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linux-7.2.3/fs/fat/.kunitconfig

@@ -0,0 +1,5 @@
+CONFIG_KUNIT=y
+CONFIG_FAT_FS=y
+CONFIG_MSDOS_FS=y
+CONFIG_VFAT_FS=y
+CONFIG_FAT_KUNIT_TEST=y

linux-7.2.3/fs/fat/Kconfig

@@ -0,0 +1,131 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config FAT_FS
+	tristate
+	select BUFFER_HEAD
+	select NLS
+	select LEGACY_DIRECT_IO
+	help
+	  If you want to use one of the FAT-based file systems (the MS-DOS and
+	  VFAT (Windows 95) file systems), then you must say Y or M here
+	  to include FAT support. You will then be able to mount partitions or
+	  diskettes with FAT-based file systems and transparently access the
+	  files on them, i.e. MSDOS files will look and behave just like all
+	  other Unix files.
+
+	  This FAT support is not a file system in itself, it only provides
+	  the foundation for the other file systems. You will have to say Y or
+	  M to at least one of "MSDOS fs support" or "VFAT fs support" in
+	  order to make use of it.
+
+	  Another way to read and write MSDOS floppies and hard drive
+	  partitions from within Linux (but not transparently) is with the
+	  mtools ("man mtools") program suite. You don't need to say Y here in
+	  order to do that.
+
+	  If you need to move large files on floppies between a DOS and a
+	  Linux box, say Y here, mount the floppy under Linux with an MSDOS
+	  file system and use GNU tar's M option. GNU tar is a program
+	  available for Unix and DOS ("man tar" or "info tar").
+
+	  The FAT support will enlarge your kernel by about 37 KB. If unsure,
+	  say Y.
+
+	  To compile this as a module, choose M here: the module will be called
+	  fat.  Note that if you compile the FAT support as a module, you
+	  cannot compile any of the FAT-based file systems into the kernel
+	  -- they will have to be modules as well.
+
+config MSDOS_FS
+	tristate "MSDOS fs support"
+	select FAT_FS
+	help
+	  This allows you to mount MSDOS partitions of your hard drive (unless
+	  they are compressed; to access compressed MSDOS partitions under
+	  Linux, you can either use the DOS emulator DOSEMU, described in the
+	  DOSEMU-HOWTO, available from
+	  <https://www.tldp.org/docs.html#howto>, or try dmsdosfs in
+	  <ftp://ibiblio.org/pub/Linux/system/filesystems/dosfs/>. If you
+	  intend to use dosemu with a non-compressed MSDOS partition, say Y
+	  here) and MSDOS floppies. This means that file access becomes
+	  transparent, i.e. the MSDOS files look and behave just like all
+	  other Unix files.
+
+	  If you have Windows 95 or Windows NT installed on your MSDOS
+	  partitions, you should use the VFAT file system (say Y to "VFAT fs
+	  support" below), or you will not be able to see the long filenames
+	  generated by Windows 95 / Windows NT.
+
+	  This option will enlarge your kernel by about 7 KB. If unsure,
+	  answer Y. This will only work if you said Y to "DOS FAT fs support"
+	  as well. To compile this as a module, choose M here: the module will
+	  be called msdos.
+
+config VFAT_FS
+	tristate "VFAT (Windows-95) fs support"
+	select FAT_FS
+	help
+	  This option provides support for normal Windows file systems with
+	  long filenames.  That includes non-compressed FAT-based file systems
+	  used by Windows 95, Windows 98, Windows NT 4.0, and the Unix
+	  programs from the mtools package.
+
+	  The VFAT support enlarges your kernel by about 10 KB and it only
+	  works if you said Y to the "DOS FAT fs support" above.  Please read
+	  the file <file:Documentation/filesystems/vfat.rst> for details.  If
+	  unsure, say Y.
+
+	  To compile this as a module, choose M here: the module will be called
+	  vfat.
+
+config FAT_DEFAULT_CODEPAGE
+	int "Default codepage for FAT"
+	depends on FAT_FS
+	default 437
+	help
+	  This option should be set to the codepage of your FAT filesystems.
+	  It can be overridden with the "codepage" mount option.
+	  See <file:Documentation/filesystems/vfat.rst> for more information.
+
+config FAT_DEFAULT_IOCHARSET
+	string "Default iocharset for FAT"
+	depends on VFAT_FS
+	default "iso8859-1"
+	help
+	  Set this to the default input/output character set you'd
+	  like FAT to use. It should probably match the character set
+	  that most of your FAT filesystems use, and can be overridden
+	  with the "iocharset" mount option for FAT filesystems.
+	  Note that "utf8" is not recommended for FAT filesystems.
+	  If unsure, you shouldn't set "utf8" here - select the next option
+	  instead if you would like to use UTF-8 encoded file names by default.
+	  See <file:Documentation/filesystems/vfat.rst> for more information.
+
+	  Enable any character sets you need in File Systems/Native Language
+	  Support.
+
+config FAT_DEFAULT_UTF8
+	bool "Enable FAT UTF-8 option by default"
+	depends on VFAT_FS
+	default n
+	help
+	  Set this if you would like to have "utf8" mount option set
+	  by default when mounting FAT filesystems.
+
+	  Even if you say Y here can always disable UTF-8 for
+	  particular mount by adding "utf8=0" to mount options.
+
+	  Say Y if you use UTF-8 encoding for file names, N otherwise.
+
+	  See <file:Documentation/filesystems/vfat.rst> for more information.
+
+config FAT_KUNIT_TEST
+	tristate "Unit Tests for FAT filesystems" if !KUNIT_ALL_TESTS
+	depends on KUNIT && FAT_FS
+	default KUNIT_ALL_TESTS
+	help
+	  This builds the FAT KUnit tests
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation in Documentation/dev-tools/kunit
+
+	  If unsure, say N

linux-7.2.3/fs/fat/Makefile

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the Linux fat filesystem support.
+#
+
+obj-$(CONFIG_FAT_FS) += fat.o
+obj-$(CONFIG_VFAT_FS) += vfat.o
+obj-$(CONFIG_MSDOS_FS) += msdos.o
+
+fat-y := cache.o dir.o fatent.o file.o inode.o misc.o nfs.o
+vfat-y := namei_vfat.o
+msdos-y := namei_msdos.o
+
+obj-$(CONFIG_FAT_KUNIT_TEST) += fat_test.o

linux-7.2.3/fs/fat/cache.c

@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  linux/fs/fat/cache.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *
+ *  Mar 1999. AV. Changed cache, so that it uses the starting cluster instead
+ *	of inode number.
+ *  May 1999. AV. Fixed the bogosity with FAT32 (read "FAT28"). Fscking lusers.
+ */
+
+#include <linux/slab.h>
+#include "fat.h"
+
+/* this must be > 0. */
+#define FAT_MAX_CACHE	8
+
+struct fat_cache {
+	struct list_head cache_list;
+	int nr_contig;	/* number of contiguous clusters */
+	int fcluster;	/* cluster number in the file. */
+	int dcluster;	/* cluster number on disk. */
+};
+
+struct fat_cache_id {
+	unsigned int id;
+	int nr_contig;
+	int fcluster;
+	int dcluster;
+};
+
+static struct kmem_cache *fat_cache_cachep;
+
+static void init_once(void *foo)
+{
+	struct fat_cache *cache = (struct fat_cache *)foo;
+
+	INIT_LIST_HEAD(&cache->cache_list);
+}
+
+int __init fat_cache_init(void)
+{
+	fat_cache_cachep = kmem_cache_create("fat_cache",
+				sizeof(struct fat_cache),
+				0, SLAB_RECLAIM_ACCOUNT,
+				init_once);
+	if (fat_cache_cachep == NULL)
+		return -ENOMEM;
+	return 0;
+}
+
+void fat_cache_destroy(void)
+{
+	kmem_cache_destroy(fat_cache_cachep);
+}
+
+static inline struct fat_cache *fat_cache_alloc(void)
+{
+	return kmem_cache_alloc(fat_cache_cachep, GFP_NOFS);
+}
+
+static inline void fat_cache_free(struct fat_cache *cache)
+{
+	BUG_ON(!list_empty(&cache->cache_list));
+	kmem_cache_free(fat_cache_cachep, cache);
+}
+
+static inline void fat_cache_update_lru(struct inode *inode,
+					struct fat_cache *cache)
+{
+	if (MSDOS_I(inode)->cache_lru.next != &cache->cache_list)
+		list_move(&cache->cache_list, &MSDOS_I(inode)->cache_lru);
+}
+
+static int fat_cache_lookup(struct inode *inode, int fclus,
+			    struct fat_cache_id *cid,
+			    int *cached_fclus, int *cached_dclus)
+{
+	static struct fat_cache nohit = { .fcluster = 0, };
+
+	struct fat_cache *hit = &nohit, *p;
+	int offset = -1;
+
+	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+	list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+		/* Find the cache of "fclus" or nearest cache. */
+		if (p->fcluster <= fclus && hit->fcluster < p->fcluster) {
+			hit = p;
+			if ((hit->fcluster + hit->nr_contig) < fclus) {
+				offset = hit->nr_contig;
+			} else {
+				offset = fclus - hit->fcluster;
+				break;
+			}
+		}
+	}
+	if (hit != &nohit) {
+		fat_cache_update_lru(inode, hit);
+
+		cid->id = MSDOS_I(inode)->cache_valid_id;
+		cid->nr_contig = hit->nr_contig;
+		cid->fcluster = hit->fcluster;
+		cid->dcluster = hit->dcluster;
+		*cached_fclus = cid->fcluster + offset;
+		*cached_dclus = cid->dcluster + offset;
+	}
+	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+
+	return offset;
+}
+
+static struct fat_cache *fat_cache_merge(struct inode *inode,
+					 struct fat_cache_id *new)
+{
+	struct fat_cache *p;
+
+	list_for_each_entry(p, &MSDOS_I(inode)->cache_lru, cache_list) {
+		/* Find the same part as "new" in cluster-chain. */
+		if (p->fcluster == new->fcluster) {
+			BUG_ON(p->dcluster != new->dcluster);
+			if (new->nr_contig > p->nr_contig)
+				p->nr_contig = new->nr_contig;
+			return p;
+		}
+	}
+	return NULL;
+}
+
+static void fat_cache_add(struct inode *inode, struct fat_cache_id *new)
+{
+	struct fat_cache *cache, *tmp;
+
+	if (new->fcluster == -1) /* dummy cache */
+		return;
+
+	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+	if (new->id != FAT_CACHE_VALID &&
+	    new->id != MSDOS_I(inode)->cache_valid_id)
+		goto out;	/* this cache was invalidated */
+
+	cache = fat_cache_merge(inode, new);
+	if (cache == NULL) {
+		if (MSDOS_I(inode)->nr_caches < FAT_MAX_CACHE) {
+			MSDOS_I(inode)->nr_caches++;
+			spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+
+			tmp = fat_cache_alloc();
+			if (!tmp) {
+				spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+				MSDOS_I(inode)->nr_caches--;
+				spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+				return;
+			}
+
+			spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+			cache = fat_cache_merge(inode, new);
+			if (cache != NULL) {
+				MSDOS_I(inode)->nr_caches--;
+				fat_cache_free(tmp);
+				goto out_update_lru;
+			}
+			cache = tmp;
+		} else {
+			struct list_head *p = MSDOS_I(inode)->cache_lru.prev;
+			cache = list_entry(p, struct fat_cache, cache_list);
+		}
+		cache->fcluster = new->fcluster;
+		cache->dcluster = new->dcluster;
+		cache->nr_contig = new->nr_contig;
+	}
+out_update_lru:
+	fat_cache_update_lru(inode, cache);
+out:
+	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+}
+
+/*
+ * Cache invalidation occurs rarely, thus the LRU chain is not updated. It
+ * fixes itself after a while.
+ */
+static void __fat_cache_inval_inode(struct inode *inode)
+{
+	struct msdos_inode_info *i = MSDOS_I(inode);
+	struct fat_cache *cache;
+
+	while (!list_empty(&i->cache_lru)) {
+		cache = list_entry(i->cache_lru.next,
+				   struct fat_cache, cache_list);
+		list_del_init(&cache->cache_list);
+		i->nr_caches--;
+		fat_cache_free(cache);
+	}
+	/* Update. The copy of caches before this id is discarded. */
+	i->cache_valid_id++;
+	if (i->cache_valid_id == FAT_CACHE_VALID)
+		i->cache_valid_id++;
+}
+
+void fat_cache_inval_inode(struct inode *inode)
+{
+	spin_lock(&MSDOS_I(inode)->cache_lru_lock);
+	__fat_cache_inval_inode(inode);
+	spin_unlock(&MSDOS_I(inode)->cache_lru_lock);
+}
+
+static inline int cache_contiguous(struct fat_cache_id *cid, int dclus)
+{
+	cid->nr_contig++;
+	return ((cid->dcluster + cid->nr_contig) == dclus);
+}
+
+static inline void cache_init(struct fat_cache_id *cid, int fclus, int dclus)
+{
+	cid->id = FAT_CACHE_VALID;
+	cid->fcluster = fclus;
+	cid->dcluster = dclus;
+	cid->nr_contig = 0;
+}
+
+int fat_get_cluster(struct inode *inode, int cluster, int *fclus, int *dclus)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const int limit = sb->s_maxbytes >> sbi->cluster_bits;
+	struct fat_entry fatent;
+	struct fat_cache_id cid;
+	int nr;
+
+	BUG_ON(MSDOS_I(inode)->i_start == 0);
+
+	*fclus = 0;
+	*dclus = MSDOS_I(inode)->i_start;
+	if (!fat_valid_entry(sbi, *dclus)) {
+		fat_fs_error_ratelimit(sb,
+			"%s: invalid start cluster (i_pos %lld, start %08x)",
+			__func__, MSDOS_I(inode)->i_pos, *dclus);
+		return -EIO;
+	}
+	if (cluster == 0)
+		return 0;
+
+	if (fat_cache_lookup(inode, cluster, &cid, fclus, dclus) < 0) {
+		/*
+		 * dummy, always not contiguous
+		 * This is reinitialized by cache_init(), later.
+		 */
+		cache_init(&cid, -1, -1);
+	}
+
+	fatent_init(&fatent);
+	while (*fclus < cluster) {
+		/* prevent the infinite loop of cluster chain */
+		if (*fclus > limit) {
+			fat_fs_error_ratelimit(sb,
+				"%s: detected the cluster chain loop (i_pos %lld)",
+				__func__, MSDOS_I(inode)->i_pos);
+			nr = -EIO;
+			goto out;
+		}
+
+		nr = fat_ent_read(inode, &fatent, *dclus);
+		if (nr < 0)
+			goto out;
+		else if (nr == FAT_ENT_FREE) {
+			fat_fs_error_ratelimit(sb,
+				"%s: invalid cluster chain (i_pos %lld)",
+				__func__, MSDOS_I(inode)->i_pos);
+			nr = -EIO;
+			goto out;
+		} else if (nr == FAT_ENT_EOF) {
+			fat_cache_add(inode, &cid);
+			goto out;
+		}
+		(*fclus)++;
+		*dclus = nr;
+		if (!cache_contiguous(&cid, *dclus))
+			cache_init(&cid, *fclus, *dclus);
+	}
+	nr = 0;
+	fat_cache_add(inode, &cid);
+out:
+	fatent_brelse(&fatent);
+	return nr;
+}
+
+static int fat_bmap_cluster(struct inode *inode, int cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	int ret, fclus, dclus;
+
+	if (MSDOS_I(inode)->i_start == 0)
+		return 0;
+
+	ret = fat_get_cluster(inode, cluster, &fclus, &dclus);
+	if (ret < 0)
+		return ret;
+	else if (ret == FAT_ENT_EOF) {
+		fat_fs_error(sb, "%s: request beyond EOF (i_pos %lld)",
+			     __func__, MSDOS_I(inode)->i_pos);
+		return -EIO;
+	}
+	return dclus;
+}
+
+int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
+			   sector_t last_block,
+			   unsigned long *mapped_blocks, sector_t *bmap)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int cluster, offset;
+
+	cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
+	offset  = sector & (sbi->sec_per_clus - 1);
+	cluster = fat_bmap_cluster(inode, cluster);
+	if (cluster < 0)
+		return cluster;
+	else if (cluster) {
+		*bmap = fat_clus_to_blknr(sbi, cluster) + offset;
+		*mapped_blocks = sbi->sec_per_clus - offset;
+		if (*mapped_blocks > last_block - sector)
+			*mapped_blocks = last_block - sector;
+	}
+
+	return 0;
+}
+
+static int is_exceed_eof(struct inode *inode, sector_t sector,
+			 sector_t *last_block, int create)
+{
+	struct super_block *sb = inode->i_sb;
+	const unsigned long blocksize = sb->s_blocksize;
+	const unsigned char blocksize_bits = sb->s_blocksize_bits;
+
+	*last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
+	if (sector >= *last_block) {
+		if (!create)
+			return 1;
+
+		/*
+		 * ->mmu_private can access on only allocation path.
+		 * (caller must hold ->i_mutex)
+		 */
+		*last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
+			>> blocksize_bits;
+		if (sector >= *last_block)
+			return 1;
+	}
+
+	return 0;
+}
+
+int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
+	     unsigned long *mapped_blocks, int create, bool from_bmap)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	sector_t last_block;
+
+	*phys = 0;
+	*mapped_blocks = 0;
+	if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) {
+		if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
+			*phys = sector + sbi->dir_start;
+			*mapped_blocks = 1;
+		}
+		return 0;
+	}
+
+	if (!from_bmap) {
+		if (is_exceed_eof(inode, sector, &last_block, create))
+			return 0;
+	} else {
+		last_block = inode->i_blocks >>
+				(inode->i_sb->s_blocksize_bits - 9);
+		if (sector >= last_block)
+			return 0;
+	}
+
+	return fat_get_mapped_cluster(inode, sector, last_block, mapped_blocks,
+				      phys);
+}

linux-7.2.3/fs/fat/fat.h

@@ -0,0 +1,493 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _FAT_H
+#define _FAT_H
+
+#include <linux/buffer_head.h>
+#include <linux/nls.h>
+#include <linux/hash.h>
+#include <linux/ratelimit.h>
+#include <linux/msdos_fs.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+
+struct file_kattr;
+
+/*
+ * vfat shortname flags
+ */
+#define VFAT_SFN_DISPLAY_LOWER	0x0001 /* convert to lowercase for display */
+#define VFAT_SFN_DISPLAY_WIN95	0x0002 /* emulate win95 rule for display */
+#define VFAT_SFN_DISPLAY_WINNT	0x0004 /* emulate winnt rule for display */
+#define VFAT_SFN_CREATE_WIN95	0x0100 /* emulate win95 rule for create */
+#define VFAT_SFN_CREATE_WINNT	0x0200 /* emulate winnt rule for create */
+
+#define FAT_ERRORS_CONT		1      /* ignore error and continue */
+#define FAT_ERRORS_PANIC	2      /* panic on error */
+#define FAT_ERRORS_RO		3      /* remount r/o on error */
+
+#define FAT_NFS_STALE_RW	1      /* NFS RW support, can cause ESTALE */
+#define FAT_NFS_NOSTALE_RO	2      /* NFS RO support, no ESTALE issue */
+
+struct fat_mount_options {
+	kuid_t fs_uid;
+	kgid_t fs_gid;
+	unsigned short fs_fmask;
+	unsigned short fs_dmask;
+	unsigned short codepage;   /* Codepage for shortname conversions */
+	int time_offset;	   /* Offset of timestamps from UTC (in minutes) */
+	char *iocharset;           /* Charset used for filename input/display */
+	unsigned short shortname;  /* flags for shortname display/create rule */
+	unsigned char name_check;  /* r = relaxed, n = normal, s = strict */
+	unsigned char errors;	   /* On error: continue, panic, remount-ro */
+	unsigned char nfs;	  /* NFS support: nostale_ro, stale_rw */
+	unsigned short allow_utime;/* permission for setting the [am]time */
+	unsigned quiet:1,          /* set = fake successful chmods and chowns */
+		 showexec:1,       /* set = only set x bit for com/exe/bat */
+		 sys_immutable:1,  /* set = system files are immutable */
+		 dotsOK:1,         /* set = hidden and system files are named '.filename' */
+		 isvfat:1,         /* 0=no vfat long filename support, 1=vfat support */
+		 utf8:1,	   /* Use of UTF-8 character set (Default) */
+		 unicode_xlate:1,  /* create escape sequences for unhandled Unicode */
+		 numtail:1,        /* Does first alias have a numeric '~1' type tail? */
+		 flush:1,	   /* write things quickly */
+		 nocase:1,	   /* Does this need case conversion? 0=need case conversion*/
+		 usefree:1,	   /* Use free_clusters for FAT32 */
+		 tz_set:1,	   /* Filesystem timestamps' offset set */
+		 rodir:1,	   /* allow ATTR_RO for directory */
+		 discard:1,	   /* Issue discard requests on deletions */
+		 dos1xfloppy:1,	   /* Assume default BPB for DOS 1.x floppies */
+		 debug:1;	   /* Not currently used */
+};
+
+#define FAT_HASH_BITS	8
+#define FAT_HASH_SIZE	(1UL << FAT_HASH_BITS)
+
+/*
+ * MS-DOS file system in-core superblock data
+ */
+struct msdos_sb_info {
+	unsigned short sec_per_clus;  /* sectors/cluster */
+	unsigned short cluster_bits;  /* log2(cluster_size) */
+	unsigned int cluster_size;    /* cluster size */
+	unsigned char fats, fat_bits; /* number of FATs, FAT bits (12,16 or 32) */
+	unsigned short fat_start;
+	unsigned long fat_length;     /* FAT start & length (sec.) */
+	unsigned long dir_start;
+	unsigned short dir_entries;   /* root dir start & entries */
+	unsigned long data_start;     /* first data sector */
+	unsigned long max_cluster;    /* maximum cluster number */
+	unsigned long root_cluster;   /* first cluster of the root directory */
+	unsigned long fsinfo_sector;  /* sector number of FAT32 fsinfo */
+	struct mutex fat_lock;
+	struct mutex nfs_build_inode_lock;
+	struct mutex s_lock;
+	unsigned int prev_free;      /* previously allocated cluster number */
+	unsigned int free_clusters;  /* -1 if undefined */
+	unsigned int free_clus_valid; /* is free_clusters valid? */
+	struct fat_mount_options options;
+	struct nls_table *nls_disk;   /* Codepage used on disk */
+	struct nls_table *nls_io;     /* Charset used for input and display */
+	const void *dir_ops;	      /* Opaque; default directory operations */
+	int dir_per_block;	      /* dir entries per block */
+	int dir_per_block_bits;	      /* log2(dir_per_block) */
+	unsigned int vol_id;		/*volume ID*/
+
+	int fatent_shift;
+	const struct fatent_operations *fatent_ops;
+	struct inode *fat_inode;
+	struct inode *fsinfo_inode;
+
+	struct ratelimit_state ratelimit;
+
+	spinlock_t inode_hash_lock;
+	struct hlist_head inode_hashtable[FAT_HASH_SIZE];
+
+	spinlock_t dir_hash_lock;
+	struct hlist_head dir_hashtable[FAT_HASH_SIZE];
+
+	unsigned int dirty;           /* fs state before mount */
+	struct rcu_head rcu;
+};
+
+#define FAT_CACHE_VALID	0	/* special case for valid cache */
+
+/*
+ * MS-DOS file system inode data in memory
+ */
+struct msdos_inode_info {
+	spinlock_t cache_lru_lock;
+	struct list_head cache_lru;
+	int nr_caches;
+	/* for avoiding the race between fat_free() and fat_get_cluster() */
+	unsigned int cache_valid_id;
+
+	/* NOTE: mmu_private is 64bits, so must hold ->i_mutex to access */
+	loff_t mmu_private;	/* physically allocated size */
+
+	int i_start;		/* first cluster or 0 */
+	int i_logstart;		/* logical first cluster */
+	int i_attrs;		/* unused attribute bits */
+	loff_t i_pos;		/* on-disk position of directory entry or 0 */
+	struct hlist_node i_fat_hash;	/* hash by i_location */
+	struct hlist_node i_dir_hash;	/* hash by i_logstart */
+	struct rw_semaphore truncate_lock; /* protect bmap against truncate */
+	struct timespec64 i_crtime;	/* File creation (birth) time */
+	struct mapping_metadata_bhs i_metadata_bhs;
+	struct inode vfs_inode;
+};
+
+struct fat_slot_info {
+	loff_t i_pos;		/* on-disk position of directory entry */
+	loff_t slot_off;	/* offset for slot or de start */
+	int nr_slots;		/* number of slots + 1(de) in filename */
+	struct msdos_dir_entry *de;
+	struct buffer_head *bh;
+};
+
+static inline struct msdos_sb_info *MSDOS_SB(struct super_block *sb)
+{
+	return sb->s_fs_info;
+}
+
+/*
+ * Functions that determine the variant of the FAT file system (i.e.,
+ * whether this is FAT12, FAT16 or FAT32.
+ */
+static inline bool is_fat12(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 12;
+}
+
+static inline bool is_fat16(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 16;
+}
+
+static inline bool is_fat32(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 32;
+}
+
+/* Maximum number of clusters */
+static inline u32 max_fat(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	return is_fat32(sbi) ? MAX_FAT32 :
+		is_fat16(sbi) ? MAX_FAT16 : MAX_FAT12;
+}
+
+static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
+{
+	return container_of(inode, struct msdos_inode_info, vfs_inode);
+}
+
+/*
+ * If ->i_mode can't hold S_IWUGO (i.e. ATTR_RO), we use ->i_attrs to
+ * save ATTR_RO instead of ->i_mode.
+ *
+ * If it's directory and !sbi->options.rodir, ATTR_RO isn't read-only
+ * bit, it's just used as flag for app.
+ */
+static inline int fat_mode_can_hold_ro(struct inode *inode)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	umode_t mask;
+
+	if (S_ISDIR(inode->i_mode)) {
+		if (!sbi->options.rodir)
+			return 0;
+		mask = ~sbi->options.fs_dmask;
+	} else
+		mask = ~sbi->options.fs_fmask;
+
+	if (!(mask & S_IWUGO))
+		return 0;
+	return 1;
+}
+
+/* Convert attribute bits and a mask to the UNIX mode. */
+static inline umode_t fat_make_mode(struct msdos_sb_info *sbi,
+				   u8 attrs, umode_t mode)
+{
+	if (attrs & ATTR_RO && !((attrs & ATTR_DIR) && !sbi->options.rodir))
+		mode &= ~S_IWUGO;
+
+	if (attrs & ATTR_DIR)
+		return (mode & ~sbi->options.fs_dmask) | S_IFDIR;
+	else
+		return (mode & ~sbi->options.fs_fmask) | S_IFREG;
+}
+
+/* Return the FAT attribute byte for this inode */
+static inline u8 fat_make_attrs(struct inode *inode)
+{
+	u8 attrs = MSDOS_I(inode)->i_attrs;
+	if (S_ISDIR(inode->i_mode))
+		attrs |= ATTR_DIR;
+	if (fat_mode_can_hold_ro(inode) && !(inode->i_mode & S_IWUGO))
+		attrs |= ATTR_RO;
+	return attrs;
+}
+
+static inline void fat_save_attrs(struct inode *inode, u8 attrs)
+{
+	if (fat_mode_can_hold_ro(inode))
+		MSDOS_I(inode)->i_attrs = attrs & ATTR_UNUSED;
+	else
+		MSDOS_I(inode)->i_attrs = attrs & (ATTR_UNUSED | ATTR_RO);
+}
+
+static inline unsigned char fat_checksum(const __u8 *name)
+{
+	unsigned char s = name[0];
+	s = (s<<7) + (s>>1) + name[1];	s = (s<<7) + (s>>1) + name[2];
+	s = (s<<7) + (s>>1) + name[3];	s = (s<<7) + (s>>1) + name[4];
+	s = (s<<7) + (s>>1) + name[5];	s = (s<<7) + (s>>1) + name[6];
+	s = (s<<7) + (s>>1) + name[7];	s = (s<<7) + (s>>1) + name[8];
+	s = (s<<7) + (s>>1) + name[9];	s = (s<<7) + (s>>1) + name[10];
+	return s;
+}
+
+static inline sector_t fat_clus_to_blknr(const struct msdos_sb_info *sbi, int clus)
+{
+	return ((sector_t)clus - FAT_START_ENT) * sbi->sec_per_clus
+		+ sbi->data_start;
+}
+
+static inline void fat_get_blknr_offset(const struct msdos_sb_info *sbi,
+				loff_t i_pos, sector_t *blknr, int *offset)
+{
+	*blknr = i_pos >> sbi->dir_per_block_bits;
+	*offset = i_pos & (sbi->dir_per_block - 1);
+}
+
+static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
+					struct inode *inode)
+{
+	loff_t i_pos;
+#if BITS_PER_LONG == 32
+	spin_lock(&sbi->inode_hash_lock);
+#endif
+	i_pos = MSDOS_I(inode)->i_pos;
+#if BITS_PER_LONG == 32
+	spin_unlock(&sbi->inode_hash_lock);
+#endif
+	return i_pos;
+}
+
+static inline void fat16_towchar(wchar_t *dst, const __u8 *src, size_t len)
+{
+#ifdef __BIG_ENDIAN
+	while (len--) {
+		*dst++ = src[0] | (src[1] << 8);
+		src += 2;
+	}
+#else
+	memcpy(dst, src, len * 2);
+#endif
+}
+
+static inline int fat_get_start(const struct msdos_sb_info *sbi,
+				const struct msdos_dir_entry *de)
+{
+	int cluster = le16_to_cpu(de->start);
+	if (is_fat32(sbi))
+		cluster |= (le16_to_cpu(de->starthi) << 16);
+	return cluster;
+}
+
+static inline void fat_set_start(struct msdos_dir_entry *de, int cluster)
+{
+	de->start   = cpu_to_le16(cluster);
+	de->starthi = cpu_to_le16(cluster >> 16);
+}
+
+static inline void fatwchar_to16(__u8 *dst, const wchar_t *src, size_t len)
+{
+#ifdef __BIG_ENDIAN
+	while (len--) {
+		dst[0] = *src & 0x00FF;
+		dst[1] = (*src & 0xFF00) >> 8;
+		dst += 2;
+		src++;
+	}
+#else
+	memcpy(dst, src, len * 2);
+#endif
+}
+
+/* fat/cache.c */
+extern void fat_cache_inval_inode(struct inode *inode);
+extern int fat_get_cluster(struct inode *inode, int cluster,
+			   int *fclus, int *dclus);
+extern int fat_get_mapped_cluster(struct inode *inode, sector_t sector,
+				  sector_t last_block,
+				  unsigned long *mapped_blocks, sector_t *bmap);
+extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
+		    unsigned long *mapped_blocks, int create, bool from_bmap);
+
+/* fat/dir.c */
+extern const struct file_operations fat_dir_operations;
+extern int fat_search_long(struct inode *inode, const unsigned char *name,
+			   int name_len, struct fat_slot_info *sinfo);
+extern int fat_dir_empty(struct inode *dir);
+extern int fat_subdirs(struct inode *dir);
+extern int fat_scan(struct inode *dir, const unsigned char *name,
+		    struct fat_slot_info *sinfo);
+extern int fat_scan_logstart(struct inode *dir, int i_logstart,
+			     struct fat_slot_info *sinfo);
+extern int fat_get_dotdot_entry(struct inode *dir, struct buffer_head **bh,
+				struct msdos_dir_entry **de);
+extern int fat_alloc_new_dir(struct inode *dir, struct timespec64 *ts);
+extern int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
+			   struct fat_slot_info *sinfo);
+extern int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo);
+
+/* fat/fatent.c */
+struct fat_entry {
+	int entry;
+	union {
+		u8 *ent12_p[2];
+		__le16 *ent16_p;
+		__le32 *ent32_p;
+	} u;
+	int nr_bhs;
+	struct buffer_head *bhs[2];
+	struct inode *fat_inode;
+};
+
+static inline void fatent_init(struct fat_entry *fatent)
+{
+	fatent->nr_bhs = 0;
+	fatent->entry = 0;
+	fatent->u.ent32_p = NULL;
+	fatent->bhs[0] = fatent->bhs[1] = NULL;
+	fatent->fat_inode = NULL;
+}
+
+static inline void fatent_set_entry(struct fat_entry *fatent, int entry)
+{
+	fatent->entry = entry;
+	fatent->u.ent32_p = NULL;
+}
+
+static inline void fatent_brelse(struct fat_entry *fatent)
+{
+	int i;
+	fatent->u.ent32_p = NULL;
+	for (i = 0; i < fatent->nr_bhs; i++)
+		brelse(fatent->bhs[i]);
+	fatent->nr_bhs = 0;
+	fatent->bhs[0] = fatent->bhs[1] = NULL;
+	fatent->fat_inode = NULL;
+}
+
+static inline bool fat_valid_entry(struct msdos_sb_info *sbi, int entry)
+{
+	return FAT_START_ENT <= entry && entry < sbi->max_cluster;
+}
+
+extern void fat_ent_access_init(struct super_block *sb);
+extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent,
+			int entry);
+extern int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
+			 int new, int wait);
+extern int fat_alloc_clusters(struct inode *inode, int *cluster,
+			      int nr_cluster);
+extern int fat_free_clusters(struct inode *inode, int cluster);
+extern int fat_count_free_clusters(struct super_block *sb);
+extern int fat_trim_fs(struct inode *inode, struct fstrim_range *range);
+
+/* fat/file.c */
+extern long fat_generic_ioctl(struct file *filp, unsigned int cmd,
+			      unsigned long arg);
+extern const struct file_operations fat_file_operations;
+extern const struct inode_operations fat_file_inode_operations;
+extern int fat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		       struct iattr *attr);
+extern void fat_truncate_blocks(struct inode *inode, loff_t offset);
+extern int fat_getattr(struct mnt_idmap *idmap,
+		       const struct path *path, struct kstat *stat,
+		       u32 request_mask, unsigned int flags);
+int fat_fileattr_get(struct dentry *dentry, struct file_kattr *fa);
+extern int fat_file_fsync(struct file *file, loff_t start, loff_t end,
+			  int datasync);
+
+/* fat/inode.c */
+extern int fat_block_truncate_page(struct inode *inode, loff_t from);
+extern void fat_attach(struct inode *inode, loff_t i_pos);
+extern void fat_detach(struct inode *inode);
+extern struct inode *fat_iget(struct super_block *sb, loff_t i_pos);
+extern struct inode *fat_build_inode(struct super_block *sb,
+			struct msdos_dir_entry *de, loff_t i_pos);
+extern int fat_sync_inode(struct inode *inode);
+extern int fat_fill_super(struct super_block *sb, struct fs_context *fc,
+			  void (*setup)(struct super_block *));
+extern int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de);
+
+extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
+			    struct inode *i2);
+
+extern const struct fs_parameter_spec fat_param_spec[];
+int fat_init_fs_context(struct fs_context *fc, bool is_vfat);
+void fat_free_fc(struct fs_context *fc);
+
+int fat_parse_param(struct fs_context *fc, struct fs_parameter *param,
+		    bool is_vfat);
+int fat_reconfigure(struct fs_context *fc);
+
+static inline unsigned long fat_dir_hash(int logstart)
+{
+	return hash_32(logstart, FAT_HASH_BITS);
+}
+extern int fat_add_cluster(struct inode *inode);
+
+/* fat/misc.c */
+extern __printf(3, 4) __cold
+void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...);
+#define fat_fs_error(sb, fmt, args...)		\
+	__fat_fs_error(sb, 1, fmt , ## args)
+#define fat_fs_error_ratelimit(sb, fmt, args...) \
+	__fat_fs_error(sb, __ratelimit(&MSDOS_SB(sb)->ratelimit), fmt , ## args)
+
+#define FAT_PRINTK_PREFIX "%sFAT-fs (%s): "
+#define fat_msg(sb, level, fmt, args...)				\
+do {									\
+	printk_index_subsys_emit(FAT_PRINTK_PREFIX, level, fmt, ##args);\
+	_fat_msg(sb, level, fmt, ##args);				\
+} while (0)
+__printf(3, 4) __cold
+void _fat_msg(struct super_block *sb, const char *level, const char *fmt, ...);
+#define fat_msg_ratelimit(sb, level, fmt, args...)	\
+	do {	\
+			if (__ratelimit(&MSDOS_SB(sb)->ratelimit))	\
+				fat_msg(sb, level, fmt, ## args);	\
+	 } while (0)
+extern int fat_clusters_flush(struct super_block *sb);
+extern int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster);
+extern void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			      __le16 __time, __le16 __date, u8 time_cs);
+extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
+			      __le16 *time, __le16 *date, u8 *time_cs);
+extern struct timespec64 fat_truncate_atime(const struct msdos_sb_info *sbi,
+					    const struct timespec64 *ts);
+#define FAT_UPDATE_ATIME	(1u << 0)
+#define FAT_UPDATE_CMTIME	(1u << 1)
+void fat_truncate_time(struct inode *inode, struct timespec64 *now,
+		unsigned int flags);
+int fat_update_time(struct inode *inode, enum fs_update_time type,
+		unsigned int flags);
+extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
+
+int fat_cache_init(void);
+void fat_cache_destroy(void);
+
+/* fat/nfs.c */
+extern const struct export_operations fat_export_ops;
+extern const struct export_operations fat_export_ops_nostale;
+
+/* helper for printk */
+typedef unsigned long long	llu;
+
+#endif /* !_FAT_H */

linux-7.2.3/fs/fat/fat_test.c

@@ -0,0 +1,395 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for FAT filesystems.
+ *
+ * Copyright (C) 2020 Google LLC.
+ * Author: David Gow <davidgow@google.com>
+ */
+
+#include <kunit/test.h>
+
+#include "fat.h"
+
+static void fat_checksum_test(struct kunit *test)
+{
+	/* With no extension. */
+	KUNIT_EXPECT_EQ(test, fat_checksum("VMLINUX    "), (u8)44);
+	/* With 3-letter extension. */
+	KUNIT_EXPECT_EQ(test, fat_checksum("README  TXT"), (u8)115);
+	/* With short (1-letter) extension. */
+	KUNIT_EXPECT_EQ(test, fat_checksum("ABCDEFGHA  "), (u8)98);
+}
+
+static void fat_clus_to_blknr_test(struct kunit *test)
+{
+	static const struct msdos_sb_info sbi = {
+		.sec_per_clus = 4,
+		.data_start = 100,
+	};
+
+	KUNIT_EXPECT_EQ(test, (sector_t)100,
+			fat_clus_to_blknr(&sbi, FAT_START_ENT));
+	KUNIT_EXPECT_EQ(test, (sector_t)112, fat_clus_to_blknr(&sbi, 5));
+}
+
+static void fat_get_blknr_offset_test(struct kunit *test)
+{
+	static const struct msdos_sb_info sbi = {
+		.dir_per_block = 16,
+		.dir_per_block_bits = 4,
+	};
+
+	sector_t blknr;
+	int offset;
+
+	fat_get_blknr_offset(&sbi, 0, &blknr, &offset);
+	KUNIT_EXPECT_EQ(test, (sector_t)0, blknr);
+	KUNIT_EXPECT_EQ(test, 0, offset);
+
+	fat_get_blknr_offset(&sbi, (10 << 4) | 7, &blknr, &offset);
+	KUNIT_EXPECT_EQ(test, (sector_t)10, blknr);
+	KUNIT_EXPECT_EQ(test, 7, offset);
+}
+
+struct fat_timestamp_testcase {
+	const char *name;
+	struct timespec64 ts;
+	__le16 time;
+	__le16 date;
+	u8 cs;
+	int time_offset;
+};
+
+struct fat_unix2fat_clamp_testcase {
+	const char *name;
+	struct timespec64 ts;
+	__le16 time;
+	__le16 date;
+	u8 cs;
+	int time_offset;
+};
+
+struct fat_truncate_atime_testcase {
+	const char *name;
+	struct timespec64 ts;
+	struct timespec64 expected;
+	int time_offset;
+};
+
+static struct fat_timestamp_testcase time_test_cases[] = {
+	{
+		.name = "Earliest possible UTC (1980-01-01 00:00:00)",
+		.ts = {.tv_sec = 315532800LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Latest possible UTC (2107-12-31 23:59:58)",
+		.ts = {.tv_sec = 4354819198LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(65439),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Earliest possible (UTC-11) (== 1979-12-31 13:00:00 UTC)",
+		.ts = {.tv_sec = 315493200LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 0,
+		.time_offset = 11 * 60,
+	},
+	{
+		.name = "Latest possible (UTC+11) (== 2108-01-01 10:59:58 UTC)",
+		.ts = {.tv_sec = 4354858798LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(65439),
+		.cs = 0,
+		.time_offset = -11 * 60,
+	},
+	{
+		.name = "Leap Day / Year (1996-02-29 00:00:00)",
+		.ts = {.tv_sec = 825552000LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(8285),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Year 2000 is leap year (2000-02-29 00:00:00)",
+		.ts = {.tv_sec = 951782400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(10333),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Year 2100 not leap year (2100-03-01 00:00:00)",
+		.ts = {.tv_sec = 4107542400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(61537),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Leap year + timezone UTC+1 (== 2004-02-29 00:30:00 UTC)",
+		.ts = {.tv_sec = 1078014600LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(48064),
+		.date = cpu_to_le16(12380),
+		.cs = 0,
+		.time_offset = -60,
+	},
+	{
+		.name = "Leap year + timezone UTC-1 (== 2004-02-29 23:30:00 UTC)",
+		.ts = {.tv_sec = 1078097400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(960),
+		.date = cpu_to_le16(12385),
+		.cs = 0,
+		.time_offset = 60,
+	},
+	{
+		.name = "VFAT odd-second resolution (1999-12-31 23:59:59)",
+		.ts = {.tv_sec = 946684799LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(10143),
+		.cs = 100,
+		.time_offset = 0,
+	},
+	{
+		.name = "VFAT 10ms resolution (1980-01-01 00:00:00:0010)",
+		.ts = {.tv_sec = 315532800LL, .tv_nsec = 10000000L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 1,
+		.time_offset = 0,
+	},
+};
+
+static struct fat_unix2fat_clamp_testcase unix2fat_clamp_test_cases[] = {
+	{
+		.name = "Clamp to earliest FAT date for 1979-12-31 23:59:59 UTC",
+		.ts = {.tv_sec = 315532799LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 0,
+		.time_offset = 0,
+	},
+	{
+		.name = "Clamp after time_offset=-60 pushes 1980-01-01 00:30 UTC below 1980",
+		.ts = {.tv_sec = 315534600LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(0),
+		.date = cpu_to_le16(33),
+		.cs = 0,
+		.time_offset = -60,
+	},
+	{
+		.name = "Clamp to latest FAT date for 2108-01-01 00:00:00 UTC",
+		.ts = {.tv_sec = 4354819200LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(65439),
+		.cs = 199,
+		.time_offset = 0,
+	},
+	{
+		.name = "Clamp after time_offset=60 pushes 2107-12-31 23:30 UTC beyond 2107",
+		.ts = {.tv_sec = 4354817400LL, .tv_nsec = 0L},
+		.time = cpu_to_le16(49021),
+		.date = cpu_to_le16(65439),
+		.cs = 199,
+		.time_offset = 60,
+	},
+};
+
+static struct fat_truncate_atime_testcase truncate_atime_test_cases[] = {
+	{
+		.name = "UTC atime truncates to 2004-02-29 00:00:00",
+		.ts = {.tv_sec = 1078058096LL, .tv_nsec = 789000000L},
+		.expected = {.tv_sec = 1078012800LL, .tv_nsec = 0L},
+		.time_offset = 0,
+	},
+	{
+		.name = "time_offset=-60 truncates 2004-02-29 00:30 UTC to previous local midnight",
+		.ts = {.tv_sec = 1078014645LL, .tv_nsec = 123000000L},
+		.expected = {.tv_sec = 1077930000LL, .tv_nsec = 0L},
+		.time_offset = -60,
+	},
+	{
+		.name = "time_offset=60 truncates 2004-02-29 23:30 UTC to next local midnight",
+		.ts = {.tv_sec = 1078097445LL, .tv_nsec = 123000000L},
+		.expected = {.tv_sec = 1078095600LL, .tv_nsec = 0L},
+		.time_offset = 60,
+	},
+};
+
+static void time_testcase_desc(struct fat_timestamp_testcase *t,
+			       char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+static void unix2fat_clamp_testcase_desc(struct fat_unix2fat_clamp_testcase *t,
+					 char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+static void truncate_atime_testcase_desc(struct fat_truncate_atime_testcase *t,
+					 char *desc)
+{
+	strscpy(desc, t->name, KUNIT_PARAM_DESC_SIZE);
+}
+
+KUNIT_ARRAY_PARAM(fat_time, time_test_cases, time_testcase_desc);
+KUNIT_ARRAY_PARAM(fat_unix2fat_clamp, unix2fat_clamp_test_cases,
+		  unix2fat_clamp_testcase_desc);
+KUNIT_ARRAY_PARAM(fat_truncate_atime, truncate_atime_test_cases,
+		  truncate_atime_testcase_desc);
+
+static void fat_test_set_time_offset(struct msdos_sb_info *sbi, int time_offset)
+{
+	memset(sbi, 0, sizeof(*sbi));
+	sbi->options.tz_set = 1;
+	sbi->options.time_offset = time_offset;
+}
+
+static void fat_time_fat2unix_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	struct timespec64 ts;
+	struct fat_timestamp_testcase *testcase =
+		(struct fat_timestamp_testcase *)test->param_value;
+
+	fat_test_set_time_offset(&fake_sb, testcase->time_offset);
+
+	fat_time_fat2unix(&fake_sb, &ts,
+			  testcase->time,
+			  testcase->date,
+			  testcase->cs);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->ts.tv_sec,
+			    ts.tv_sec,
+			    "Timestamp mismatch (seconds)\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->ts.tv_nsec,
+			    ts.tv_nsec,
+			    "Timestamp mismatch (nanoseconds)\n");
+}
+
+static void fat_time_unix2fat_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	__le16 date, time;
+	u8 cs;
+	struct fat_timestamp_testcase *testcase =
+		(struct fat_timestamp_testcase *)test->param_value;
+
+	fat_test_set_time_offset(&fake_sb, testcase->time_offset);
+
+	fat_time_unix2fat(&fake_sb, &testcase->ts,
+			  &time, &date, &cs);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->time,
+			    time,
+			    "Time mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->date,
+			    date,
+			    "Date mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->cs,
+			    cs,
+			    "Centisecond mismatch\n");
+}
+
+static void fat_time_unix2fat_clamp_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	__le16 date, time;
+	u8 cs;
+	struct fat_unix2fat_clamp_testcase *testcase =
+		(struct fat_unix2fat_clamp_testcase *)test->param_value;
+
+	fat_test_set_time_offset(&fake_sb, testcase->time_offset);
+
+	fat_time_unix2fat(&fake_sb, &testcase->ts, &time, &date, &cs);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->time,
+			    time,
+			    "Clamped time mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->date,
+			    date,
+			    "Clamped date mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->cs,
+			    cs,
+			    "Clamped centisecond mismatch\n");
+}
+
+static void fat_time_unix2fat_no_csec_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	struct timespec64 ts = {
+		.tv_sec = 946684799LL,
+		.tv_nsec = 0L,
+	};
+	__le16 date, time;
+
+	fat_test_set_time_offset(&fake_sb, 0);
+
+	fat_time_unix2fat(&fake_sb, &ts, &time, &date, NULL);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    49021,
+			    le16_to_cpu(time),
+			    "Time mismatch without centiseconds\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    10143,
+			    le16_to_cpu(date),
+			    "Date mismatch without centiseconds\n");
+}
+
+static void fat_truncate_atime_test(struct kunit *test)
+{
+	static struct msdos_sb_info fake_sb;
+	struct timespec64 actual;
+	struct fat_truncate_atime_testcase *testcase =
+		(struct fat_truncate_atime_testcase *)test->param_value;
+
+	fat_test_set_time_offset(&fake_sb, testcase->time_offset);
+
+	actual = fat_truncate_atime(&fake_sb, &testcase->ts);
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->expected.tv_sec,
+			    actual.tv_sec,
+			    "Atime truncation seconds mismatch\n");
+	KUNIT_EXPECT_EQ_MSG(test,
+			    testcase->expected.tv_nsec,
+			    actual.tv_nsec,
+			    "Atime truncation nanoseconds mismatch\n");
+}
+
+static struct kunit_case fat_test_cases[] = {
+	KUNIT_CASE(fat_checksum_test),
+	KUNIT_CASE(fat_clus_to_blknr_test),
+	KUNIT_CASE(fat_get_blknr_offset_test),
+	KUNIT_CASE_PARAM(fat_time_fat2unix_test, fat_time_gen_params),
+	KUNIT_CASE_PARAM(fat_time_unix2fat_test, fat_time_gen_params),
+	KUNIT_CASE_PARAM(fat_time_unix2fat_clamp_test,
+			 fat_unix2fat_clamp_gen_params),
+	KUNIT_CASE(fat_time_unix2fat_no_csec_test),
+	KUNIT_CASE_PARAM(fat_truncate_atime_test,
+			 fat_truncate_atime_gen_params),
+	{},
+};
+
+static struct kunit_suite fat_test_suite = {
+	.name = "fat_test",
+	.test_cases = fat_test_cases,
+};
+
+kunit_test_suites(&fat_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for FAT filesystems");
+MODULE_LICENSE("GPL v2");

linux-7.2.3/fs/fat/fatent.c

@@ -0,0 +1,853 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2004, OGAWA Hirofumi
+ */
+
+#include <linux/blkdev.h>
+#include <linux/sched/signal.h>
+#include <linux/backing-dev-defs.h>
+#include "fat.h"
+
+struct fatent_operations {
+	void (*ent_blocknr)(struct super_block *, int, int *, sector_t *);
+	void (*ent_set_ptr)(struct fat_entry *, int);
+	int (*ent_bread)(struct super_block *, struct fat_entry *,
+			 int, sector_t);
+	int (*ent_get)(struct fat_entry *);
+	void (*ent_put)(struct fat_entry *, int);
+	int (*ent_next)(struct fat_entry *);
+};
+
+static DEFINE_SPINLOCK(fat12_entry_lock);
+
+static void fat12_ent_blocknr(struct super_block *sb, int entry,
+			      int *offset, sector_t *blocknr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int bytes = entry + (entry >> 1);
+	WARN_ON(!fat_valid_entry(sbi, entry));
+	*offset = bytes & (sb->s_blocksize - 1);
+	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
+}
+
+static void fat_ent_blocknr(struct super_block *sb, int entry,
+			    int *offset, sector_t *blocknr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int bytes = (entry << sbi->fatent_shift);
+	WARN_ON(!fat_valid_entry(sbi, entry));
+	*offset = bytes & (sb->s_blocksize - 1);
+	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
+}
+
+static void fat12_ent_set_ptr(struct fat_entry *fatent, int offset)
+{
+	struct buffer_head **bhs = fatent->bhs;
+	if (fatent->nr_bhs == 1) {
+		WARN_ON(offset >= (bhs[0]->b_size - 1));
+		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
+		fatent->u.ent12_p[1] = bhs[0]->b_data + (offset + 1);
+	} else {
+		WARN_ON(offset != (bhs[0]->b_size - 1));
+		fatent->u.ent12_p[0] = bhs[0]->b_data + offset;
+		fatent->u.ent12_p[1] = bhs[1]->b_data;
+	}
+}
+
+static void fat16_ent_set_ptr(struct fat_entry *fatent, int offset)
+{
+	WARN_ON(offset & (2 - 1));
+	fatent->u.ent16_p = (__le16 *)(fatent->bhs[0]->b_data + offset);
+}
+
+static void fat32_ent_set_ptr(struct fat_entry *fatent, int offset)
+{
+	WARN_ON(offset & (4 - 1));
+	fatent->u.ent32_p = (__le32 *)(fatent->bhs[0]->b_data + offset);
+}
+
+static int fat12_ent_bread(struct super_block *sb, struct fat_entry *fatent,
+			   int offset, sector_t blocknr)
+{
+	struct buffer_head **bhs = fatent->bhs;
+
+	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
+	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
+
+	bhs[0] = sb_bread(sb, blocknr);
+	if (!bhs[0])
+		goto err;
+
+	if ((offset + 1) < sb->s_blocksize)
+		fatent->nr_bhs = 1;
+	else {
+		/* This entry is block boundary, it needs the next block */
+		blocknr++;
+		bhs[1] = sb_bread(sb, blocknr);
+		if (!bhs[1])
+			goto err_brelse;
+		fatent->nr_bhs = 2;
+	}
+	fat12_ent_set_ptr(fatent, offset);
+	return 0;
+
+err_brelse:
+	brelse(bhs[0]);
+err:
+	fat_msg_ratelimit(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
+			  (llu)blocknr);
+	return -EIO;
+}
+
+static int fat_ent_bread(struct super_block *sb, struct fat_entry *fatent,
+			 int offset, sector_t blocknr)
+{
+	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+
+	WARN_ON(blocknr < MSDOS_SB(sb)->fat_start);
+	fatent->fat_inode = MSDOS_SB(sb)->fat_inode;
+	fatent->bhs[0] = sb_bread(sb, blocknr);
+	if (!fatent->bhs[0]) {
+		fat_msg_ratelimit(sb, KERN_ERR, "FAT read failed (blocknr %llu)",
+				  (llu)blocknr);
+		return -EIO;
+	}
+	fatent->nr_bhs = 1;
+	ops->ent_set_ptr(fatent, offset);
+	return 0;
+}
+
+static int fat12_ent_get(struct fat_entry *fatent)
+{
+	u8 **ent12_p = fatent->u.ent12_p;
+	int next;
+
+	spin_lock(&fat12_entry_lock);
+	if (fatent->entry & 1)
+		next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
+	else
+		next = (*ent12_p[1] << 8) | *ent12_p[0];
+	spin_unlock(&fat12_entry_lock);
+
+	next &= 0x0fff;
+	if (next >= BAD_FAT12)
+		next = FAT_ENT_EOF;
+	return next;
+}
+
+static int fat16_ent_get(struct fat_entry *fatent)
+{
+	int next = le16_to_cpu(*fatent->u.ent16_p);
+	WARN_ON((unsigned long)fatent->u.ent16_p & (2 - 1));
+	if (next >= BAD_FAT16)
+		next = FAT_ENT_EOF;
+	return next;
+}
+
+static int fat32_ent_get(struct fat_entry *fatent)
+{
+	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
+	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
+	if (next >= BAD_FAT32)
+		next = FAT_ENT_EOF;
+	return next;
+}
+
+static void fat12_ent_put(struct fat_entry *fatent, int new)
+{
+	u8 **ent12_p = fatent->u.ent12_p;
+
+	if (new == FAT_ENT_EOF)
+		new = EOF_FAT12;
+
+	spin_lock(&fat12_entry_lock);
+	if (fatent->entry & 1) {
+		*ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
+		*ent12_p[1] = new >> 4;
+	} else {
+		*ent12_p[0] = new & 0xff;
+		*ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
+	}
+	spin_unlock(&fat12_entry_lock);
+
+	mmb_mark_buffer_dirty(fatent->bhs[0],
+			      &MSDOS_I(fatent->fat_inode)->i_metadata_bhs);
+	if (fatent->nr_bhs == 2)
+		mmb_mark_buffer_dirty(fatent->bhs[1],
+				&MSDOS_I(fatent->fat_inode)->i_metadata_bhs);
+}
+
+static void fat16_ent_put(struct fat_entry *fatent, int new)
+{
+	if (new == FAT_ENT_EOF)
+		new = EOF_FAT16;
+
+	*fatent->u.ent16_p = cpu_to_le16(new);
+	mmb_mark_buffer_dirty(fatent->bhs[0],
+			      &MSDOS_I(fatent->fat_inode)->i_metadata_bhs);
+}
+
+static void fat32_ent_put(struct fat_entry *fatent, int new)
+{
+	WARN_ON(new & 0xf0000000);
+	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
+	*fatent->u.ent32_p = cpu_to_le32(new);
+	mmb_mark_buffer_dirty(fatent->bhs[0],
+			      &MSDOS_I(fatent->fat_inode)->i_metadata_bhs);
+}
+
+static int fat12_ent_next(struct fat_entry *fatent)
+{
+	u8 **ent12_p = fatent->u.ent12_p;
+	struct buffer_head **bhs = fatent->bhs;
+	u8 *nextp = ent12_p[1] + 1 + (fatent->entry & 1);
+
+	fatent->entry++;
+	if (fatent->nr_bhs == 1) {
+		WARN_ON(ent12_p[0] > (u8 *)(bhs[0]->b_data +
+							(bhs[0]->b_size - 2)));
+		WARN_ON(ent12_p[1] > (u8 *)(bhs[0]->b_data +
+							(bhs[0]->b_size - 1)));
+		if (nextp < (u8 *)(bhs[0]->b_data + (bhs[0]->b_size - 1))) {
+			ent12_p[0] = nextp - 1;
+			ent12_p[1] = nextp;
+			return 1;
+		}
+	} else {
+		WARN_ON(ent12_p[0] != (u8 *)(bhs[0]->b_data +
+							(bhs[0]->b_size - 1)));
+		WARN_ON(ent12_p[1] != (u8 *)bhs[1]->b_data);
+		ent12_p[0] = nextp - 1;
+		ent12_p[1] = nextp;
+		brelse(bhs[0]);
+		bhs[0] = bhs[1];
+		fatent->nr_bhs = 1;
+		return 1;
+	}
+	ent12_p[0] = NULL;
+	ent12_p[1] = NULL;
+	return 0;
+}
+
+static int fat16_ent_next(struct fat_entry *fatent)
+{
+	const struct buffer_head *bh = fatent->bhs[0];
+	fatent->entry++;
+	if (fatent->u.ent16_p < (__le16 *)(bh->b_data + (bh->b_size - 2))) {
+		fatent->u.ent16_p++;
+		return 1;
+	}
+	fatent->u.ent16_p = NULL;
+	return 0;
+}
+
+static int fat32_ent_next(struct fat_entry *fatent)
+{
+	const struct buffer_head *bh = fatent->bhs[0];
+	fatent->entry++;
+	if (fatent->u.ent32_p < (__le32 *)(bh->b_data + (bh->b_size - 4))) {
+		fatent->u.ent32_p++;
+		return 1;
+	}
+	fatent->u.ent32_p = NULL;
+	return 0;
+}
+
+static const struct fatent_operations fat12_ops = {
+	.ent_blocknr	= fat12_ent_blocknr,
+	.ent_set_ptr	= fat12_ent_set_ptr,
+	.ent_bread	= fat12_ent_bread,
+	.ent_get	= fat12_ent_get,
+	.ent_put	= fat12_ent_put,
+	.ent_next	= fat12_ent_next,
+};
+
+static const struct fatent_operations fat16_ops = {
+	.ent_blocknr	= fat_ent_blocknr,
+	.ent_set_ptr	= fat16_ent_set_ptr,
+	.ent_bread	= fat_ent_bread,
+	.ent_get	= fat16_ent_get,
+	.ent_put	= fat16_ent_put,
+	.ent_next	= fat16_ent_next,
+};
+
+static const struct fatent_operations fat32_ops = {
+	.ent_blocknr	= fat_ent_blocknr,
+	.ent_set_ptr	= fat32_ent_set_ptr,
+	.ent_bread	= fat_ent_bread,
+	.ent_get	= fat32_ent_get,
+	.ent_put	= fat32_ent_put,
+	.ent_next	= fat32_ent_next,
+};
+
+static inline void lock_fat(struct msdos_sb_info *sbi)
+{
+	mutex_lock(&sbi->fat_lock);
+}
+
+static inline void unlock_fat(struct msdos_sb_info *sbi)
+{
+	mutex_unlock(&sbi->fat_lock);
+}
+
+void fat_ent_access_init(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	mutex_init(&sbi->fat_lock);
+
+	if (is_fat32(sbi)) {
+		sbi->fatent_shift = 2;
+		sbi->fatent_ops = &fat32_ops;
+	} else if (is_fat16(sbi)) {
+		sbi->fatent_shift = 1;
+		sbi->fatent_ops = &fat16_ops;
+	} else if (is_fat12(sbi)) {
+		sbi->fatent_shift = -1;
+		sbi->fatent_ops = &fat12_ops;
+	} else {
+		fat_fs_error(sb, "invalid FAT variant, %u bits", sbi->fat_bits);
+	}
+}
+
+static void mark_fsinfo_dirty(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (sb_rdonly(sb) || !is_fat32(sbi))
+		return;
+
+	__mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
+}
+
+static inline int fat_ent_update_ptr(struct super_block *sb,
+				     struct fat_entry *fatent,
+				     int offset, sector_t blocknr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct buffer_head **bhs = fatent->bhs;
+
+	/* Is this fatent's blocks including this entry? */
+	if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
+		return 0;
+	if (is_fat12(sbi)) {
+		if ((offset + 1) < sb->s_blocksize) {
+			/* This entry is on bhs[0]. */
+			if (fatent->nr_bhs == 2) {
+				brelse(bhs[1]);
+				fatent->nr_bhs = 1;
+			}
+		} else {
+			/* This entry needs the next block. */
+			if (fatent->nr_bhs != 2)
+				return 0;
+			if (bhs[1]->b_blocknr != (blocknr + 1))
+				return 0;
+		}
+	}
+	ops->ent_set_ptr(fatent, offset);
+	return 1;
+}
+
+int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	int err, offset;
+	sector_t blocknr;
+
+	if (!fat_valid_entry(sbi, entry)) {
+		fatent_brelse(fatent);
+		fat_fs_error_ratelimit(sb, "invalid access to FAT (entry 0x%08x)", entry);
+		return -EIO;
+	}
+
+	fatent_set_entry(fatent, entry);
+	ops->ent_blocknr(sb, entry, &offset, &blocknr);
+
+	if (!fat_ent_update_ptr(sb, fatent, offset, blocknr)) {
+		fatent_brelse(fatent);
+		err = ops->ent_bread(sb, fatent, offset, blocknr);
+		if (err)
+			return err;
+	}
+	return ops->ent_get(fatent);
+}
+
+/* FIXME: We can write the blocks as more big chunk. */
+static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs,
+			  int nr_bhs)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *c_bh;
+	int err, n, copy;
+
+	err = 0;
+	for (copy = 1; copy < sbi->fats; copy++) {
+		sector_t backup_fat = sbi->fat_length * copy;
+
+		for (n = 0; n < nr_bhs; n++) {
+			c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr);
+			if (!c_bh) {
+				err = -ENOMEM;
+				goto error;
+			}
+			/* Avoid race with userspace read via bdev */
+			lock_buffer(c_bh);
+			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
+			set_buffer_uptodate(c_bh);
+			unlock_buffer(c_bh);
+			mmb_mark_buffer_dirty(c_bh,
+				&MSDOS_I(sbi->fat_inode)->i_metadata_bhs);
+			if (sb->s_flags & SB_SYNCHRONOUS)
+				err = sync_dirty_buffer(c_bh);
+			brelse(c_bh);
+			if (err)
+				goto error;
+		}
+	}
+error:
+	return err;
+}
+
+int fat_ent_write(struct inode *inode, struct fat_entry *fatent,
+		  int new, int wait)
+{
+	struct super_block *sb = inode->i_sb;
+	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+	int err;
+
+	ops->ent_put(fatent, new);
+	if (wait) {
+		err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs);
+		if (err)
+			return err;
+	}
+	return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs);
+}
+
+static inline int fat_ent_next(struct msdos_sb_info *sbi,
+			       struct fat_entry *fatent)
+{
+	if (sbi->fatent_ops->ent_next(fatent)) {
+		if (fatent->entry < sbi->max_cluster)
+			return 1;
+	}
+	return 0;
+}
+
+static inline int fat_ent_read_block(struct super_block *sb,
+				     struct fat_entry *fatent)
+{
+	const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops;
+	sector_t blocknr;
+	int offset;
+
+	fatent_brelse(fatent);
+	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+	return ops->ent_bread(sb, fatent, offset, blocknr);
+}
+
+static void fat_collect_bhs(struct buffer_head **bhs, int *nr_bhs,
+			    struct fat_entry *fatent)
+{
+	int n, i;
+
+	for (n = 0; n < fatent->nr_bhs; n++) {
+		for (i = 0; i < *nr_bhs; i++) {
+			if (fatent->bhs[n] == bhs[i])
+				break;
+		}
+		if (i == *nr_bhs) {
+			get_bh(fatent->bhs[n]);
+			bhs[i] = fatent->bhs[n];
+			(*nr_bhs)++;
+		}
+	}
+}
+
+int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent, prev_ent;
+	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
+	int i, count, err, nr_bhs, idx_clus;
+
+	BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));	/* fixed limit */
+
+	lock_fat(sbi);
+	if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
+	    sbi->free_clusters < nr_cluster) {
+		unlock_fat(sbi);
+		return -ENOSPC;
+	}
+
+	err = nr_bhs = idx_clus = 0;
+	count = FAT_START_ENT;
+	fatent_init(&prev_ent);
+	fatent_init(&fatent);
+	fatent_set_entry(&fatent, sbi->prev_free + 1);
+	while (count < sbi->max_cluster) {
+		if (fatent.entry >= sbi->max_cluster)
+			fatent.entry = FAT_START_ENT;
+		fatent_set_entry(&fatent, fatent.entry);
+		err = fat_ent_read_block(sb, &fatent);
+		if (err)
+			goto out;
+
+		/* Find the free entries in a block */
+		do {
+			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
+				int entry = fatent.entry;
+
+				/* make the cluster chain */
+				ops->ent_put(&fatent, FAT_ENT_EOF);
+				if (prev_ent.nr_bhs)
+					ops->ent_put(&prev_ent, entry);
+
+				fat_collect_bhs(bhs, &nr_bhs, &fatent);
+
+				sbi->prev_free = entry;
+				if (sbi->free_clusters != -1)
+					sbi->free_clusters--;
+
+				cluster[idx_clus] = entry;
+				idx_clus++;
+				if (idx_clus == nr_cluster)
+					goto out;
+
+				/*
+				 * fat_collect_bhs() gets ref-count of bhs,
+				 * so we can still use the prev_ent.
+				 */
+				prev_ent = fatent;
+			}
+			count++;
+			if (count == sbi->max_cluster)
+				break;
+		} while (fat_ent_next(sbi, &fatent));
+	}
+
+	/* Couldn't allocate the free entries */
+	sbi->free_clusters = 0;
+	sbi->free_clus_valid = 1;
+	err = -ENOSPC;
+
+out:
+	unlock_fat(sbi);
+	mark_fsinfo_dirty(sb);
+	fatent_brelse(&fatent);
+	if (!err) {
+		if (inode_needs_sync(inode))
+			err = fat_sync_bhs(bhs, nr_bhs);
+		if (!err)
+			err = fat_mirror_bhs(sb, bhs, nr_bhs);
+	}
+	for (i = 0; i < nr_bhs; i++)
+		brelse(bhs[i]);
+
+	if (err && idx_clus)
+		fat_free_clusters(inode, cluster[0]);
+
+	return err;
+}
+
+int fat_free_clusters(struct inode *inode, int cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent;
+	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
+	int i, err, nr_bhs;
+	int first_cl = cluster, dirty_fsinfo = 0;
+
+	nr_bhs = 0;
+	fatent_init(&fatent);
+	lock_fat(sbi);
+	do {
+		cluster = fat_ent_read(inode, &fatent, cluster);
+		if (cluster < 0) {
+			err = cluster;
+			goto error;
+		} else if (cluster == FAT_ENT_FREE) {
+			fat_fs_error(sb, "%s: deleting FAT entry beyond EOF",
+				     __func__);
+			err = -EIO;
+			goto error;
+		}
+
+		if (sbi->options.discard) {
+			/*
+			 * Issue discard for the sectors we no longer
+			 * care about, batching contiguous clusters
+			 * into one request
+			 */
+			if (cluster != fatent.entry + 1) {
+				int nr_clus = fatent.entry - first_cl + 1;
+
+				sb_issue_discard(sb,
+					fat_clus_to_blknr(sbi, first_cl),
+					nr_clus * sbi->sec_per_clus,
+					GFP_NOFS, 0);
+
+				first_cl = cluster;
+			}
+		}
+
+		ops->ent_put(&fatent, FAT_ENT_FREE);
+		if (sbi->free_clusters != -1) {
+			sbi->free_clusters++;
+			dirty_fsinfo = 1;
+		}
+
+		if (nr_bhs + fatent.nr_bhs > MAX_BUF_PER_PAGE) {
+			if (sb->s_flags & SB_SYNCHRONOUS) {
+				err = fat_sync_bhs(bhs, nr_bhs);
+				if (err)
+					goto error;
+			}
+			err = fat_mirror_bhs(sb, bhs, nr_bhs);
+			if (err)
+				goto error;
+			for (i = 0; i < nr_bhs; i++)
+				brelse(bhs[i]);
+			nr_bhs = 0;
+		}
+		fat_collect_bhs(bhs, &nr_bhs, &fatent);
+	} while (cluster != FAT_ENT_EOF);
+
+	if (sb->s_flags & SB_SYNCHRONOUS) {
+		err = fat_sync_bhs(bhs, nr_bhs);
+		if (err)
+			goto error;
+	}
+	err = fat_mirror_bhs(sb, bhs, nr_bhs);
+error:
+	fatent_brelse(&fatent);
+	for (i = 0; i < nr_bhs; i++)
+		brelse(bhs[i]);
+	unlock_fat(sbi);
+	if (dirty_fsinfo)
+		mark_fsinfo_dirty(sb);
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(fat_free_clusters);
+
+struct fatent_ra {
+	sector_t cur;
+	sector_t limit;
+
+	unsigned int ra_blocks;
+	sector_t ra_advance;
+	sector_t ra_next;
+	sector_t ra_limit;
+};
+
+static void fat_ra_init(struct super_block *sb, struct fatent_ra *ra,
+			struct fat_entry *fatent, int ent_limit)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	sector_t blocknr, block_end;
+	int offset;
+	/*
+	 * This is the sequential read, so ra_pages * 2 (but try to
+	 * align the optimal hardware IO size).
+	 * [BTW, 128kb covers the whole sectors for FAT12 and FAT16]
+	 */
+	unsigned long ra_pages = sb->s_bdi->ra_pages;
+	unsigned int reada_blocks;
+
+	if (fatent->entry >= ent_limit)
+		return;
+
+	if (ra_pages > sb->s_bdi->io_pages)
+		ra_pages = rounddown(ra_pages, sb->s_bdi->io_pages);
+	reada_blocks = ra_pages << (PAGE_SHIFT - sb->s_blocksize_bits + 1);
+
+	/* Initialize the range for sequential read */
+	ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+	ops->ent_blocknr(sb, ent_limit - 1, &offset, &block_end);
+	ra->cur = 0;
+	ra->limit = (block_end + 1) - blocknr;
+
+	/* Advancing the window at half size */
+	ra->ra_blocks = reada_blocks >> 1;
+	ra->ra_advance = ra->cur;
+	ra->ra_next = ra->cur;
+	ra->ra_limit = ra->cur + min_t(sector_t, reada_blocks, ra->limit);
+}
+
+/* Assuming to be called before reading a new block (increments ->cur). */
+static void fat_ent_reada(struct super_block *sb, struct fatent_ra *ra,
+			  struct fat_entry *fatent)
+{
+	if (ra->ra_next >= ra->ra_limit)
+		return;
+
+	if (ra->cur >= ra->ra_advance) {
+		struct msdos_sb_info *sbi = MSDOS_SB(sb);
+		const struct fatent_operations *ops = sbi->fatent_ops;
+		struct blk_plug plug;
+		sector_t blocknr, diff;
+		int offset;
+
+		ops->ent_blocknr(sb, fatent->entry, &offset, &blocknr);
+
+		diff = blocknr - ra->cur;
+		blk_start_plug(&plug);
+		/*
+		 * FIXME: we would want to directly use the bio with
+		 * pages to reduce the number of segments.
+		 */
+		for (; ra->ra_next < ra->ra_limit; ra->ra_next++)
+			sb_breadahead(sb, ra->ra_next + diff);
+		blk_finish_plug(&plug);
+
+		/* Advance the readahead window */
+		ra->ra_advance += ra->ra_blocks;
+		ra->ra_limit += min_t(sector_t,
+				      ra->ra_blocks, ra->limit - ra->ra_limit);
+	}
+	ra->cur++;
+}
+
+int fat_count_free_clusters(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent;
+	struct fatent_ra fatent_ra;
+	int err = 0, free;
+
+	lock_fat(sbi);
+	if (sbi->free_clusters != -1 && sbi->free_clus_valid)
+		goto out;
+
+	free = 0;
+	fatent_init(&fatent);
+	fatent_set_entry(&fatent, FAT_START_ENT);
+	fat_ra_init(sb, &fatent_ra, &fatent, sbi->max_cluster);
+	while (fatent.entry < sbi->max_cluster) {
+		/* readahead of fat blocks */
+		fat_ent_reada(sb, &fatent_ra, &fatent);
+
+		err = fat_ent_read_block(sb, &fatent);
+		if (err)
+			goto out;
+
+		do {
+			if (ops->ent_get(&fatent) == FAT_ENT_FREE)
+				free++;
+		} while (fat_ent_next(sbi, &fatent));
+		cond_resched();
+	}
+	sbi->free_clusters = free;
+	sbi->free_clus_valid = 1;
+	mark_fsinfo_dirty(sb);
+	fatent_brelse(&fatent);
+out:
+	unlock_fat(sbi);
+	return err;
+}
+
+static int fat_trim_clusters(struct super_block *sb, u32 clus, u32 nr_clus)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	return sb_issue_discard(sb, fat_clus_to_blknr(sbi, clus),
+				nr_clus * sbi->sec_per_clus, GFP_NOFS, 0);
+}
+
+int fat_trim_fs(struct inode *inode, struct fstrim_range *range)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	const struct fatent_operations *ops = sbi->fatent_ops;
+	struct fat_entry fatent;
+	struct fatent_ra fatent_ra;
+	u64 ent_start, ent_end, minlen, trimmed = 0;
+	u32 free = 0;
+	int err = 0;
+
+	/*
+	 * FAT data is organized as clusters, trim at the granulary of cluster.
+	 *
+	 * fstrim_range is in byte, convert values to cluster index.
+	 * Treat sectors before data region as all used, not to trim them.
+	 */
+	ent_start = max_t(u64, range->start>>sbi->cluster_bits, FAT_START_ENT);
+	ent_end = ent_start + (range->len >> sbi->cluster_bits) - 1;
+	minlen = range->minlen >> sbi->cluster_bits;
+
+	if (ent_start >= sbi->max_cluster || range->len < sbi->cluster_size)
+		return -EINVAL;
+	if (ent_end >= sbi->max_cluster)
+		ent_end = sbi->max_cluster - 1;
+
+	fatent_init(&fatent);
+	lock_fat(sbi);
+	fatent_set_entry(&fatent, ent_start);
+	fat_ra_init(sb, &fatent_ra, &fatent, ent_end + 1);
+	while (fatent.entry <= ent_end) {
+		/* readahead of fat blocks */
+		fat_ent_reada(sb, &fatent_ra, &fatent);
+
+		err = fat_ent_read_block(sb, &fatent);
+		if (err)
+			goto error;
+		do {
+			if (ops->ent_get(&fatent) == FAT_ENT_FREE) {
+				free++;
+			} else if (free) {
+				if (free >= minlen) {
+					u32 clus = fatent.entry - free;
+
+					err = fat_trim_clusters(sb, clus, free);
+					if (err && err != -EOPNOTSUPP)
+						goto error;
+					if (!err)
+						trimmed += free;
+					err = 0;
+				}
+				free = 0;
+			}
+		} while (fat_ent_next(sbi, &fatent) && fatent.entry <= ent_end);
+
+		if (fatal_signal_pending(current)) {
+			err = -ERESTARTSYS;
+			goto error;
+		}
+
+		if (need_resched()) {
+			fatent_brelse(&fatent);
+			unlock_fat(sbi);
+			cond_resched();
+			lock_fat(sbi);
+		}
+	}
+	/* handle scenario when tail entries are all free */
+	if (free && free >= minlen) {
+		u32 clus = fatent.entry - free;
+
+		err = fat_trim_clusters(sb, clus, free);
+		if (err && err != -EOPNOTSUPP)
+			goto error;
+		if (!err)
+			trimmed += free;
+		err = 0;
+	}
+
+error:
+	fatent_brelse(&fatent);
+	unlock_fat(sbi);
+
+	range->len = trimmed << sbi->cluster_bits;
+
+	return err;
+}

linux-7.2.3/fs/fat/file.c

@@ -0,0 +1,615 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/fat/file.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *
+ *  regular file handling primitives for fat-based filesystems
+ */
+
+#include <linux/capability.h>
+#include <linux/module.h>
+#include <linux/compat.h>
+#include <linux/mount.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/filelock.h>
+#include <linux/fsnotify.h>
+#include <linux/security.h>
+#include <linux/falloc.h>
+#include <linux/fileattr.h>
+#include "fat.h"
+
+static long fat_fallocate(struct file *file, int mode,
+			  loff_t offset, loff_t len);
+
+static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
+{
+	u32 attr;
+
+	inode_lock_shared(inode);
+	attr = fat_make_attrs(inode);
+	inode_unlock_shared(inode);
+
+	return put_user(attr, user_attr);
+}
+
+static int fat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
+{
+	struct inode *inode = file_inode(file);
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	int is_dir = S_ISDIR(inode->i_mode);
+	u32 attr, oldattr;
+	struct iattr ia;
+	int err;
+
+	err = get_user(attr, user_attr);
+	if (err)
+		goto out;
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+	inode_lock(inode);
+
+	/*
+	 * ATTR_VOLUME and ATTR_DIR cannot be changed; this also
+	 * prevents the user from turning us into a VFAT
+	 * longname entry.  Also, we obviously can't set
+	 * any of the NTFS attributes in the high 24 bits.
+	 */
+	attr &= 0xff & ~(ATTR_VOLUME | ATTR_DIR);
+	/* Merge in ATTR_VOLUME and ATTR_DIR */
+	attr |= (MSDOS_I(inode)->i_attrs & ATTR_VOLUME) |
+		(is_dir ? ATTR_DIR : 0);
+	oldattr = fat_make_attrs(inode);
+
+	/* Equivalent to a chmod() */
+	ia.ia_valid = ATTR_MODE | ATTR_CTIME;
+	ia.ia_ctime = current_time(inode);
+	if (is_dir)
+		ia.ia_mode = fat_make_mode(sbi, attr, S_IRWXUGO);
+	else {
+		ia.ia_mode = fat_make_mode(sbi, attr,
+			S_IRUGO | S_IWUGO | (inode->i_mode & S_IXUGO));
+	}
+
+	/* The root directory has no attributes */
+	if (inode->i_ino == MSDOS_ROOT_INO && attr != ATTR_DIR) {
+		err = -EINVAL;
+		goto out_unlock_inode;
+	}
+
+	if (sbi->options.sys_immutable &&
+	    ((attr | oldattr) & ATTR_SYS) &&
+	    !capable(CAP_LINUX_IMMUTABLE)) {
+		err = -EPERM;
+		goto out_unlock_inode;
+	}
+
+	/*
+	 * The security check is questionable...  We single
+	 * out the RO attribute for checking by the security
+	 * module, just because it maps to a file mode.
+	 */
+	err = security_inode_setattr(file_mnt_idmap(file),
+				     file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	/* This MUST be done before doing anything irreversible... */
+	err = fat_setattr(file_mnt_idmap(file), file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	fsnotify_change(file->f_path.dentry, ia.ia_valid);
+	if (sbi->options.sys_immutable) {
+		if (attr & ATTR_SYS)
+			inode->i_flags |= S_IMMUTABLE;
+		else
+			inode->i_flags &= ~S_IMMUTABLE;
+	}
+
+	fat_save_attrs(inode, attr);
+	mark_inode_dirty(inode);
+out_unlock_inode:
+	inode_unlock(inode);
+	mnt_drop_write_file(file);
+out:
+	return err;
+}
+
+static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	return put_user(sbi->vol_id, user_attr);
+}
+
+static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
+{
+	struct super_block *sb = inode->i_sb;
+	struct fstrim_range __user *user_range;
+	struct fstrim_range range;
+	int err;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (!bdev_max_discard_sectors(sb->s_bdev))
+		return -EOPNOTSUPP;
+
+	user_range = (struct fstrim_range __user *)arg;
+	if (copy_from_user(&range, user_range, sizeof(range)))
+		return -EFAULT;
+
+	range.minlen = max(range.minlen, bdev_discard_granularity(sb->s_bdev));
+
+	err = fat_trim_fs(inode, &range);
+	if (err < 0)
+		return err;
+
+	if (copy_to_user(user_range, &range, sizeof(range)))
+		return -EFAULT;
+
+	return 0;
+}
+
+long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	u32 __user *user_attr = (u32 __user *)arg;
+
+	switch (cmd) {
+	case FAT_IOCTL_GET_ATTRIBUTES:
+		return fat_ioctl_get_attributes(inode, user_attr);
+	case FAT_IOCTL_SET_ATTRIBUTES:
+		return fat_ioctl_set_attributes(filp, user_attr);
+	case FAT_IOCTL_GET_VOLUME_ID:
+		return fat_ioctl_get_volume_id(inode, user_attr);
+	case FITRIM:
+		return fat_ioctl_fitrim(inode, arg);
+	default:
+		return -ENOTTY;	/* Inappropriate ioctl for device */
+	}
+}
+
+static int fat_file_release(struct inode *inode, struct file *filp)
+{
+	if ((filp->f_mode & FMODE_WRITE) &&
+	    MSDOS_SB(inode->i_sb)->options.flush) {
+		fat_flush_inodes(inode->i_sb, inode, NULL);
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		io_schedule_timeout(HZ/10);
+	}
+	return 0;
+}
+
+int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = filp->f_mapping->host;
+	struct inode *fat_inode = MSDOS_SB(inode->i_sb)->fat_inode;
+	int err;
+
+	err = mmb_fsync_noflush(filp, &MSDOS_I(inode)->i_metadata_bhs,
+				start, end, datasync);
+	if (err)
+		return err;
+
+	err = mmb_sync(&MSDOS_I(fat_inode)->i_metadata_bhs);
+	if (err)
+		return err;
+
+	return blkdev_issue_flush(inode->i_sb->s_bdev);
+}
+
+
+const struct file_operations fat_file_operations = {
+	.llseek		= generic_file_llseek,
+	.read_iter	= generic_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.mmap_prepare	= generic_file_mmap_prepare,
+	.release	= fat_file_release,
+	.unlocked_ioctl	= fat_generic_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+	.fsync		= fat_file_fsync,
+	.splice_read	= filemap_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.fallocate	= fat_fallocate,
+	.setlease	= generic_setlease,
+};
+
+static int fat_cont_expand(struct inode *inode, loff_t size)
+{
+	struct address_space *mapping = inode->i_mapping;
+	loff_t start = inode->i_size, count = size - inode->i_size;
+	int err;
+
+	err = generic_cont_expand_simple(inode, size);
+	if (err)
+		goto out;
+
+	fat_truncate_time(inode, NULL, FAT_UPDATE_CMTIME);
+	mark_inode_dirty(inode);
+	if (IS_SYNC(inode)) {
+		int err2;
+
+		/*
+		 * Opencode syncing since we don't have a file open to use
+		 * standard fsync path.
+		 */
+		err = filemap_fdatawrite_range(mapping, start,
+					       start + count - 1);
+		err2 = mmb_sync(&MSDOS_I(inode)->i_metadata_bhs);
+		if (!err)
+			err = err2;
+		err2 = write_inode_now(inode, 1);
+		if (!err)
+			err = err2;
+		if (!err) {
+			err =  filemap_fdatawait_range(mapping, start,
+						       start + count - 1);
+		}
+	}
+out:
+	return err;
+}
+
+/*
+ * Preallocate space for a file. This implements fat's fallocate file
+ * operation, which gets called from sys_fallocate system call. User
+ * space requests len bytes at offset. If FALLOC_FL_KEEP_SIZE is set
+ * we just allocate clusters without zeroing them out. Otherwise we
+ * allocate and zero out clusters via an expanding truncate.
+ */
+static long fat_fallocate(struct file *file, int mode,
+			  loff_t offset, loff_t len)
+{
+	int nr_cluster; /* Number of clusters to be allocated */
+	loff_t mm_bytes; /* Number of bytes to be allocated for file */
+	loff_t ondisksize; /* block aligned on-disk size in bytes*/
+	struct inode *inode = file->f_mapping->host;
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int err = 0;
+
+	/* No support for hole punch or other fallocate flags. */
+	if (mode & ~FALLOC_FL_KEEP_SIZE)
+		return -EOPNOTSUPP;
+
+	/* No support for dir */
+	if (!S_ISREG(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	inode_lock(inode);
+	if (mode & FALLOC_FL_KEEP_SIZE) {
+		ondisksize = inode->i_blocks << 9;
+		if ((offset + len) <= ondisksize)
+			goto error;
+
+		/* First compute the number of clusters to be allocated */
+		mm_bytes = offset + len - ondisksize;
+		nr_cluster = (mm_bytes + (sbi->cluster_size - 1)) >>
+			sbi->cluster_bits;
+
+		/* Start the allocation.We are not zeroing out the clusters */
+		while (nr_cluster-- > 0) {
+			err = fat_add_cluster(inode);
+			if (err)
+				goto error;
+		}
+	} else {
+		if ((offset + len) <= i_size_read(inode))
+			goto error;
+
+		/* This is just an expanding truncate */
+		err = fat_cont_expand(inode, (offset + len));
+	}
+
+error:
+	inode_unlock(inode);
+	return err;
+}
+
+/* Free all clusters after the skip'th cluster. */
+static int fat_free(struct inode *inode, int skip)
+{
+	struct super_block *sb = inode->i_sb;
+	int err, wait, free_start, i_start, i_logstart;
+
+	if (MSDOS_I(inode)->i_start == 0)
+		return 0;
+
+	fat_cache_inval_inode(inode);
+
+	wait = IS_DIRSYNC(inode);
+	i_start = free_start = MSDOS_I(inode)->i_start;
+	i_logstart = MSDOS_I(inode)->i_logstart;
+
+	/* First, we write the new file size. */
+	if (!skip) {
+		MSDOS_I(inode)->i_start = 0;
+		MSDOS_I(inode)->i_logstart = 0;
+	}
+	MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
+	fat_truncate_time(inode, NULL, FAT_UPDATE_CMTIME);
+	if (wait) {
+		err = fat_sync_inode(inode);
+		if (err) {
+			MSDOS_I(inode)->i_start = i_start;
+			MSDOS_I(inode)->i_logstart = i_logstart;
+			return err;
+		}
+	} else
+		mark_inode_dirty(inode);
+
+	/* Write a new EOF, and get the remaining cluster chain for freeing. */
+	if (skip) {
+		struct fat_entry fatent;
+		int ret, fclus, dclus;
+
+		ret = fat_get_cluster(inode, skip - 1, &fclus, &dclus);
+		if (ret < 0)
+			return ret;
+		else if (ret == FAT_ENT_EOF)
+			return 0;
+
+		fatent_init(&fatent);
+		ret = fat_ent_read(inode, &fatent, dclus);
+		if (ret == FAT_ENT_EOF) {
+			fatent_brelse(&fatent);
+			return 0;
+		} else if (ret == FAT_ENT_FREE) {
+			fat_fs_error(sb,
+				     "%s: invalid cluster chain (i_pos %lld)",
+				     __func__, MSDOS_I(inode)->i_pos);
+			ret = -EIO;
+		} else if (ret > 0) {
+			err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait);
+			if (err)
+				ret = err;
+		}
+		fatent_brelse(&fatent);
+		if (ret < 0)
+			return ret;
+
+		free_start = ret;
+	}
+	inode->i_blocks = skip << (MSDOS_SB(sb)->cluster_bits - 9);
+
+	/* Freeing the remained cluster chain */
+	return fat_free_clusters(inode, free_start);
+}
+
+void fat_truncate_blocks(struct inode *inode, loff_t offset)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	const unsigned int cluster_size = sbi->cluster_size;
+	int nr_clusters;
+
+	/*
+	 * This protects against truncating a file bigger than it was then
+	 * trying to write into the hole.
+	 */
+	if (MSDOS_I(inode)->mmu_private > offset)
+		MSDOS_I(inode)->mmu_private = offset;
+
+	nr_clusters = (offset + (cluster_size - 1)) >> sbi->cluster_bits;
+
+	fat_free(inode, nr_clusters);
+	fat_flush_inodes(inode->i_sb, inode, NULL);
+}
+
+int fat_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
+	bool case_sensitive;
+
+	/*
+	 * FAT filesystems are case-insensitive by default. VFAT
+	 * becomes case-sensitive when mounted with 'check=strict',
+	 * which installs vfat_dentry_ops. MSDOS has no such option;
+	 * its 'nocase' mount option selects case-sensitive matching.
+	 *
+	 * VFAT long filename entries preserve case. Without VFAT, only
+	 * uppercased 8.3 short names are stored. MSDOS with 'nocase'
+	 * also preserves case.
+	 */
+	if (sbi->options.isvfat)
+		case_sensitive = sbi->options.name_check == 's';
+	else
+		case_sensitive = sbi->options.nocase;
+
+	if (!case_sensitive) {
+		fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
+		fa->flags |= FS_CASEFOLD_FL;
+		if (!sbi->options.isvfat)
+			fa->fsx_xflags |= FS_XFLAG_CASENONPRESERVING;
+	}
+	if (d_inode(dentry)->i_flags & S_IMMUTABLE) {
+		fa->fsx_xflags |= FS_XFLAG_IMMUTABLE;
+		fa->flags |= FS_IMMUTABLE_FL;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_fileattr_get);
+
+int fat_getattr(struct mnt_idmap *idmap, const struct path *path,
+		struct kstat *stat, u32 request_mask, unsigned int flags)
+{
+	struct inode *inode = d_inode(path->dentry);
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+
+	generic_fillattr(idmap, request_mask, inode, stat);
+	stat->blksize = sbi->cluster_size;
+
+	if (sbi->options.nfs == FAT_NFS_NOSTALE_RO) {
+		/* Use i_pos for ino. This is used as fileid of nfs. */
+		stat->ino = fat_i_pos_read(sbi, inode);
+	}
+
+	if (sbi->options.isvfat && request_mask & STATX_BTIME) {
+		stat->result_mask |= STATX_BTIME;
+		stat->btime = MSDOS_I(inode)->i_crtime;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_getattr);
+
+static int fat_sanitize_mode(const struct msdos_sb_info *sbi,
+			     struct inode *inode, umode_t *mode_ptr)
+{
+	umode_t mask, perm;
+
+	/*
+	 * Note, the basic check is already done by a caller of
+	 * (attr->ia_mode & ~FAT_VALID_MODE)
+	 */
+
+	if (S_ISREG(inode->i_mode))
+		mask = sbi->options.fs_fmask;
+	else
+		mask = sbi->options.fs_dmask;
+
+	perm = *mode_ptr & ~(S_IFMT | mask);
+
+	/*
+	 * Of the r and x bits, all (subject to umask) must be present. Of the
+	 * w bits, either all (subject to umask) or none must be present.
+	 *
+	 * If fat_mode_can_hold_ro(inode) is false, can't change w bits.
+	 */
+	if ((perm & (S_IRUGO | S_IXUGO)) != (inode->i_mode & (S_IRUGO|S_IXUGO)))
+		return -EPERM;
+	if (fat_mode_can_hold_ro(inode)) {
+		if ((perm & S_IWUGO) && ((perm & S_IWUGO) != (S_IWUGO & ~mask)))
+			return -EPERM;
+	} else {
+		if ((perm & S_IWUGO) != (S_IWUGO & ~mask))
+			return -EPERM;
+	}
+
+	*mode_ptr &= S_IFMT | perm;
+
+	return 0;
+}
+
+static int fat_allow_set_time(struct mnt_idmap *idmap,
+			      struct msdos_sb_info *sbi, struct inode *inode)
+{
+	umode_t allow_utime = sbi->options.allow_utime;
+
+	if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode),
+			    current_fsuid())) {
+		if (vfsgid_in_group_p(i_gid_into_vfsgid(idmap, inode)))
+			allow_utime >>= 3;
+		if (allow_utime & MAY_WRITE)
+			return 1;
+	}
+
+	/* use a default check */
+	return 0;
+}
+
+#define TIMES_SET_FLAGS	(ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)
+/* valid file mode bits */
+#define FAT_VALID_MODE	(S_IFREG | S_IFDIR | S_IRWXUGO)
+
+int fat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		struct iattr *attr)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
+	struct inode *inode = d_inode(dentry);
+	unsigned int ia_valid;
+	int error;
+
+	/* Check for setting the inode time. */
+	ia_valid = attr->ia_valid;
+	if (ia_valid & TIMES_SET_FLAGS) {
+		if (fat_allow_set_time(idmap, sbi, inode))
+			attr->ia_valid &= ~TIMES_SET_FLAGS;
+	}
+
+	error = setattr_prepare(idmap, dentry, attr);
+	attr->ia_valid = ia_valid;
+	if (error) {
+		if (sbi->options.quiet)
+			error = 0;
+		goto out;
+	}
+
+	/*
+	 * Expand the file. Since inode_setattr() updates ->i_size
+	 * before calling the ->truncate(), but FAT needs to fill the
+	 * hole before it. XXX: this is no longer true with new truncate
+	 * sequence.
+	 */
+	if (attr->ia_valid & ATTR_SIZE) {
+		inode_dio_wait(inode);
+
+		if (attr->ia_size > inode->i_size) {
+			error = fat_cont_expand(inode, attr->ia_size);
+			if (error || attr->ia_valid == ATTR_SIZE)
+				goto out;
+			attr->ia_valid &= ~ATTR_SIZE;
+		}
+	}
+
+	if (((attr->ia_valid & ATTR_UID) &&
+	     (!uid_eq(from_vfsuid(idmap, i_user_ns(inode), attr->ia_vfsuid),
+		      sbi->options.fs_uid))) ||
+	    ((attr->ia_valid & ATTR_GID) &&
+	     (!gid_eq(from_vfsgid(idmap, i_user_ns(inode), attr->ia_vfsgid),
+		      sbi->options.fs_gid))) ||
+	    ((attr->ia_valid & ATTR_MODE) &&
+	     (attr->ia_mode & ~FAT_VALID_MODE)))
+		error = -EPERM;
+
+	if (error) {
+		if (sbi->options.quiet)
+			error = 0;
+		goto out;
+	}
+
+	/*
+	 * We don't return -EPERM here. Yes, strange, but this is too
+	 * old behavior.
+	 */
+	if (attr->ia_valid & ATTR_MODE) {
+		if (fat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
+			attr->ia_valid &= ~ATTR_MODE;
+	}
+
+	if (attr->ia_valid & ATTR_SIZE) {
+		error = fat_block_truncate_page(inode, attr->ia_size);
+		if (error)
+			goto out;
+		down_write(&MSDOS_I(inode)->truncate_lock);
+		truncate_setsize(inode, attr->ia_size);
+		fat_truncate_blocks(inode, attr->ia_size);
+		up_write(&MSDOS_I(inode)->truncate_lock);
+	}
+
+	/*
+	 * setattr_copy can't truncate these appropriately, so we'll copy them
+	 * ourselves.  See fat_truncate_time for the c/mtime logic on fat.
+	 */
+	if (attr->ia_valid & ATTR_ATIME)
+		fat_truncate_time(inode, &attr->ia_atime, FAT_UPDATE_ATIME);
+	if (attr->ia_valid & ATTR_MTIME)
+		fat_truncate_time(inode, &attr->ia_mtime, FAT_UPDATE_CMTIME);
+	attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
+
+	setattr_copy(idmap, inode, attr);
+	mark_inode_dirty(inode);
+out:
+	return error;
+}
+EXPORT_SYMBOL_GPL(fat_setattr);
+
+const struct inode_operations fat_file_inode_operations = {
+	.setattr	= fat_setattr,
+	.getattr	= fat_getattr,
+	.fileattr_get	= fat_fileattr_get,
+	.update_time	= fat_update_time,
+};

linux-7.2.3/fs/fat/misc.c

@@ -0,0 +1,362 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/fat/misc.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *  22/11/2000 - Fixed fat_date_unix2dos for dates earlier than 01/01/1980
+ *		 and date_dos2unix for date==0 by Igor Zhbanov(bsg@uniyar.ac.ru)
+ */
+
+#include "fat.h"
+#include <linux/iversion.h>
+
+/*
+ * fat_fs_error reports a file system problem that might indicate fa data
+ * corruption/inconsistency. Depending on 'errors' mount option the
+ * panic() is called, or error message is printed FAT and nothing is done,
+ * or filesystem is remounted read-only (default behavior).
+ * In case the file system is remounted read-only, it can be made writable
+ * again by remounting it.
+ */
+void __fat_fs_error(struct super_block *sb, int report, const char *fmt, ...)
+{
+	struct fat_mount_options *opts = &MSDOS_SB(sb)->options;
+	va_list args;
+	struct va_format vaf;
+
+	if (report) {
+		va_start(args, fmt);
+		vaf.fmt = fmt;
+		vaf.va = &args;
+		fat_msg(sb, KERN_ERR, "error, %pV", &vaf);
+		va_end(args);
+	}
+
+	if (opts->errors == FAT_ERRORS_PANIC)
+		panic("FAT-fs (%s): fs panic from previous error\n", sb->s_id);
+	else if (opts->errors == FAT_ERRORS_RO && !sb_rdonly(sb)) {
+		sb->s_flags |= SB_RDONLY;
+		fat_msg(sb, KERN_ERR, "Filesystem has been set read-only");
+	}
+}
+EXPORT_SYMBOL_GPL(__fat_fs_error);
+
+/**
+ * _fat_msg() - Print a preformatted FAT message based on a superblock.
+ * @sb: A pointer to a &struct super_block
+ * @level: A Kernel printk level constant
+ * @fmt: The printf-style format string to print.
+ *
+ * Everything that is not fat_fs_error() should be fat_msg().
+ *
+ * fat_msg() wraps _fat_msg() for printk indexing.
+ */
+void _fat_msg(struct super_block *sb, const char *level, const char *fmt, ...)
+{
+	struct va_format vaf;
+	va_list args;
+
+	va_start(args, fmt);
+	vaf.fmt = fmt;
+	vaf.va = &args;
+	_printk(FAT_PRINTK_PREFIX "%pV\n", level, sb->s_id, &vaf);
+	va_end(args);
+}
+
+/* Flushes the number of free clusters on FAT32 */
+/* XXX: Need to write one per FSINFO block.  Currently only writes 1 */
+int fat_clusters_flush(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct buffer_head *bh;
+	struct fat_boot_fsinfo *fsinfo;
+
+	if (!is_fat32(sbi))
+		return 0;
+
+	bh = sb_bread(sb, sbi->fsinfo_sector);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR, "bread failed in fat_clusters_flush");
+		return -EIO;
+	}
+
+	fsinfo = (struct fat_boot_fsinfo *)bh->b_data;
+	/* Sanity check */
+	if (!IS_FSINFO(fsinfo)) {
+		fat_msg(sb, KERN_ERR, "Invalid FSINFO signature: "
+		       "0x%08x, 0x%08x (sector = %lu)",
+		       le32_to_cpu(fsinfo->signature1),
+		       le32_to_cpu(fsinfo->signature2),
+		       sbi->fsinfo_sector);
+	} else {
+		if (sbi->free_clusters != -1)
+			fsinfo->free_clusters = cpu_to_le32(sbi->free_clusters);
+		if (sbi->prev_free != -1)
+			fsinfo->next_cluster = cpu_to_le32(sbi->prev_free);
+		mark_buffer_dirty(bh);
+	}
+	brelse(bh);
+
+	return 0;
+}
+
+/*
+ * fat_chain_add() adds a new cluster to the chain of clusters represented
+ * by inode.
+ */
+int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster)
+{
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	int ret, new_fclus, last;
+
+	/*
+	 * We must locate the last cluster of the file to add this new
+	 * one (new_dclus) to the end of the link list (the FAT).
+	 */
+	last = new_fclus = 0;
+	if (MSDOS_I(inode)->i_start) {
+		int fclus, dclus;
+
+		ret = fat_get_cluster(inode, FAT_ENT_EOF, &fclus, &dclus);
+		if (ret < 0)
+			return ret;
+		new_fclus = fclus + 1;
+		last = dclus;
+	}
+
+	/* add new one to the last of the cluster chain */
+	if (last) {
+		struct fat_entry fatent;
+
+		fatent_init(&fatent);
+		ret = fat_ent_read(inode, &fatent, last);
+		if (ret >= 0) {
+			int wait = inode_needs_sync(inode);
+			ret = fat_ent_write(inode, &fatent, new_dclus, wait);
+			fatent_brelse(&fatent);
+		}
+		if (ret < 0)
+			return ret;
+		/*
+		 * FIXME:Although we can add this cache, fat_cache_add() is
+		 * assuming to be called after linear search with fat_cache_id.
+		 */
+//		fat_cache_add(inode, new_fclus, new_dclus);
+	} else {
+		MSDOS_I(inode)->i_start = new_dclus;
+		MSDOS_I(inode)->i_logstart = new_dclus;
+		/*
+		 * Since generic_write_sync() synchronizes regular files later,
+		 * we sync here only directories.
+		 */
+		if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode)) {
+			ret = fat_sync_inode(inode);
+			if (ret)
+				return ret;
+		} else
+			mark_inode_dirty(inode);
+	}
+	if (new_fclus != (inode->i_blocks >> (sbi->cluster_bits - 9))) {
+		fat_fs_error_ratelimit(
+			sb, "clusters badly computed (%d != %llu)", new_fclus,
+			(llu)(inode->i_blocks >> (sbi->cluster_bits - 9)));
+		fat_cache_inval_inode(inode);
+	}
+	inode->i_blocks += nr_cluster << (sbi->cluster_bits - 9);
+
+	return 0;
+}
+
+/*
+ * The epoch of FAT timestamp is 1980.
+ *     :  bits :     value
+ * date:  0 -  4: day	(1 -  31)
+ * date:  5 -  8: month	(1 -  12)
+ * date:  9 - 15: year	(0 - 127) from 1980
+ * time:  0 -  4: sec	(0 -  29) 2sec counts
+ * time:  5 - 10: min	(0 -  59)
+ * time: 11 - 15: hour	(0 -  23)
+ */
+#define SECS_PER_MIN	60
+#define SECS_PER_HOUR	(60 * 60)
+#define SECS_PER_DAY	(SECS_PER_HOUR * 24)
+/* days between 1.1.70 and 1.1.80 (2 leap days) */
+#define DAYS_DELTA	(365 * 10 + 2)
+/* 120 (2100 - 1980) isn't leap year */
+#define YEAR_2100	120
+#define IS_LEAP_YEAR(y)	(!((y) & 3) && (y) != YEAR_2100)
+
+/* Linear day numbers of the respective 1sts in non-leap years. */
+static long days_in_year[] = {
+	/* Jan  Feb  Mar  Apr  May  Jun  Jul  Aug  Sep  Oct  Nov  Dec */
+	0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,
+};
+
+static inline int fat_tz_offset(const struct msdos_sb_info *sbi)
+{
+	return (sbi->options.tz_set ?
+	       -sbi->options.time_offset :
+	       sys_tz.tz_minuteswest) * SECS_PER_MIN;
+}
+
+/* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */
+void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
+		       __le16 __time, __le16 __date, u8 time_cs)
+{
+	u16 time = le16_to_cpu(__time), date = le16_to_cpu(__date);
+	time64_t second;
+	long day, leap_day, month, year;
+
+	year  = date >> 9;
+	month = max(1, (date >> 5) & 0xf);
+	day   = max(1, date & 0x1f) - 1;
+
+	leap_day = (year + 3) / 4;
+	if (year > YEAR_2100)		/* 2100 isn't leap year */
+		leap_day--;
+	if (IS_LEAP_YEAR(year) && month > 2)
+		leap_day++;
+
+	second =  (time & 0x1f) << 1;
+	second += ((time >> 5) & 0x3f) * SECS_PER_MIN;
+	second += (time >> 11) * SECS_PER_HOUR;
+	second += (time64_t)(year * 365 + leap_day
+		   + days_in_year[month] + day
+		   + DAYS_DELTA) * SECS_PER_DAY;
+
+	second += fat_tz_offset(sbi);
+
+	if (time_cs) {
+		ts->tv_sec = second + (time_cs / 100);
+		ts->tv_nsec = (time_cs % 100) * 10000000;
+	} else {
+		ts->tv_sec = second;
+		ts->tv_nsec = 0;
+	}
+}
+
+/* Export fat_time_fat2unix() for the fat_test KUnit tests. */
+EXPORT_SYMBOL_GPL(fat_time_fat2unix);
+
+/* Convert linear UNIX date to a FAT time/date pair. */
+void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
+		       __le16 *time, __le16 *date, u8 *time_cs)
+{
+	struct tm tm;
+	time64_to_tm(ts->tv_sec, -fat_tz_offset(sbi), &tm);
+
+	/*  FAT can only support year between 1980 to 2107 */
+	if (tm.tm_year < 1980 - 1900) {
+		*time = 0;
+		*date = cpu_to_le16((0 << 9) | (1 << 5) | 1);
+		if (time_cs)
+			*time_cs = 0;
+		return;
+	}
+	if (tm.tm_year > 2107 - 1900) {
+		*time = cpu_to_le16((23 << 11) | (59 << 5) | 29);
+		*date = cpu_to_le16((127 << 9) | (12 << 5) | 31);
+		if (time_cs)
+			*time_cs = 199;
+		return;
+	}
+
+	/* from 1900 -> from 1980 */
+	tm.tm_year -= 80;
+	/* 0~11 -> 1~12 */
+	tm.tm_mon++;
+	/* 0~59 -> 0~29(2sec counts) */
+	tm.tm_sec >>= 1;
+
+	*time = cpu_to_le16(tm.tm_hour << 11 | tm.tm_min << 5 | tm.tm_sec);
+	*date = cpu_to_le16(tm.tm_year << 9 | tm.tm_mon << 5 | tm.tm_mday);
+	if (time_cs)
+		*time_cs = (ts->tv_sec & 1) * 100 + ts->tv_nsec / 10000000;
+}
+EXPORT_SYMBOL_GPL(fat_time_unix2fat);
+
+static inline struct timespec64 fat_timespec64_trunc_2secs(struct timespec64 ts)
+{
+	return (struct timespec64){ ts.tv_sec & ~1ULL, 0 };
+}
+
+/*
+ * truncate atime to 24 hour granularity (00:00:00 in local timezone)
+ */
+struct timespec64 fat_truncate_atime(const struct msdos_sb_info *sbi,
+				     const struct timespec64 *ts)
+{
+	/* to localtime */
+	time64_t seconds = ts->tv_sec - fat_tz_offset(sbi);
+	s32 remainder;
+
+	div_s64_rem(seconds, SECS_PER_DAY, &remainder);
+	/* to day boundary, and back to unix time */
+	seconds = seconds + fat_tz_offset(sbi) - remainder;
+
+	return (struct timespec64){ seconds, 0 };
+}
+/* Export fat_truncate_atime() for the fat_test KUnit tests. */
+EXPORT_SYMBOL_GPL(fat_truncate_atime);
+
+/*
+ * Update the in-inode atime and/or mtime after truncating the timestamp to the
+ * granularity.  All timestamps in root inode are always 0.
+ *
+ * ctime and mtime share the same on-disk field, and should be identical in
+ * memory.  All mtime updates will be applied to ctime, but ctime updates are
+ * ignored.
+ */
+void fat_truncate_time(struct inode *inode, struct timespec64 *now,
+		unsigned int flags)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	struct timespec64 ts;
+
+	if (inode->i_ino == MSDOS_ROOT_INO)
+		return;
+
+	if (now == NULL) {
+		now = &ts;
+		ts = current_time(inode);
+	}
+
+	if (flags & FAT_UPDATE_ATIME)
+		inode_set_atime_to_ts(inode, fat_truncate_atime(sbi, now));
+	if (flags & FAT_UPDATE_CMTIME) {
+		/* truncate mtime to 2 second granularity */
+		struct timespec64 mtime = fat_timespec64_trunc_2secs(*now);
+
+		inode_set_mtime_to_ts(inode, mtime);
+		inode_set_ctime_to_ts(inode, mtime);
+	}
+}
+EXPORT_SYMBOL_GPL(fat_truncate_time);
+
+int fat_update_time(struct inode *inode, enum fs_update_time type,
+		unsigned int flags)
+{
+	if (inode->i_ino != MSDOS_ROOT_INO) {
+		fat_truncate_time(inode, NULL, type == FS_UPD_ATIME ?
+				FAT_UPDATE_ATIME : FAT_UPDATE_CMTIME);
+		__mark_inode_dirty(inode, inode_time_dirty_flag(inode));
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_update_time);
+
+int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
+{
+	int i, err = 0;
+
+	for (i = 0; i < nr_bhs; i++)
+		write_dirty_buffer(bhs[i], 0);
+
+	for (i = 0; i < nr_bhs; i++) {
+		wait_on_buffer(bhs[i]);
+		if (!err && !buffer_uptodate(bhs[i]))
+			err = -EIO;
+	}
+	return err;
+}

linux-7.2.3/fs/fat/namei_msdos.c

@@ -0,0 +1,718 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/fs/msdos/namei.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ *  Hidden files 1995 by Albert Cahalan <albert@ccs.neu.edu> <adc@coe.neu.edu>
+ *  Rewritten for constant inumbers 1999 by Al Viro
+ */
+
+#include <linux/module.h>
+#include <linux/iversion.h>
+#include "fat.h"
+
+/* Characters that are undesirable in an MS-DOS file name */
+static unsigned char bad_chars[] = "*?<>|\"";
+static unsigned char bad_if_strict[] = "+=,; ";
+
+/***** Formats an MS-DOS file name. Rejects invalid names. */
+static int msdos_format_name(const unsigned char *name, int len,
+			     unsigned char *res, struct fat_mount_options *opts)
+	/*
+	 * name is the proposed name, len is its length, res is
+	 * the resulting name, opts->name_check is either (r)elaxed,
+	 * (n)ormal or (s)trict, opts->dotsOK allows dots at the
+	 * beginning of name (for hidden files)
+	 */
+{
+	unsigned char *walk;
+	unsigned char c;
+	int space;
+
+	if (name[0] == '.') {	/* dotfile because . and .. already done */
+		if (opts->dotsOK) {
+			/* Get rid of dot - test for it elsewhere */
+			name++;
+			len--;
+		} else
+			return -EINVAL;
+	}
+	/*
+	 * disallow names that _really_ start with a dot
+	 */
+	space = 1;
+	c = 0;
+	for (walk = res; len && walk - res < 8; walk++) {
+		c = *name++;
+		len--;
+		if (opts->name_check != 'r' && strchr(bad_chars, c))
+			return -EINVAL;
+		if (opts->name_check == 's' && strchr(bad_if_strict, c))
+			return -EINVAL;
+		if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
+			return -EINVAL;
+		if (c < ' ' || c == ':' || c == '\\')
+			return -EINVAL;
+	/*
+	 * 0xE5 is legal as a first character, but we must substitute
+	 * 0x05 because 0xE5 marks deleted files.  Yes, DOS really
+	 * does this.
+	 * It seems that Microsoft hacked DOS to support non-US
+	 * characters after the 0xE5 character was already in use to
+	 * mark deleted files.
+	 */
+		if ((res == walk) && (c == 0xE5))
+			c = 0x05;
+		if (c == '.')
+			break;
+		space = (c == ' ');
+		*walk = (!opts->nocase && c >= 'a' && c <= 'z') ? c - 32 : c;
+	}
+	if (space)
+		return -EINVAL;
+	if (opts->name_check == 's' && len && c != '.') {
+		c = *name++;
+		len--;
+		if (c != '.')
+			return -EINVAL;
+	}
+	while (c != '.' && len--)
+		c = *name++;
+	if (c == '.') {
+		while (walk - res < 8)
+			*walk++ = ' ';
+		while (len > 0 && walk - res < MSDOS_NAME) {
+			c = *name++;
+			len--;
+			if (opts->name_check != 'r' && strchr(bad_chars, c))
+				return -EINVAL;
+			if (opts->name_check == 's' &&
+			    strchr(bad_if_strict, c))
+				return -EINVAL;
+			if (c < ' ' || c == ':' || c == '\\')
+				return -EINVAL;
+			if (c == '.') {
+				if (opts->name_check == 's')
+					return -EINVAL;
+				break;
+			}
+			if (c >= 'A' && c <= 'Z' && opts->name_check == 's')
+				return -EINVAL;
+			space = c == ' ';
+			if (!opts->nocase && c >= 'a' && c <= 'z')
+				*walk++ = c - 32;
+			else
+				*walk++ = c;
+		}
+		if (space)
+			return -EINVAL;
+		if (opts->name_check == 's' && len)
+			return -EINVAL;
+	}
+	while (walk - res < MSDOS_NAME)
+		*walk++ = ' ';
+
+	return 0;
+}
+
+/***** Locates a directory entry.  Uses unformatted name. */
+static int msdos_find(struct inode *dir, const unsigned char *name, int len,
+		      struct fat_slot_info *sinfo)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
+	unsigned char msdos_name[MSDOS_NAME];
+	int err;
+
+	err = msdos_format_name(name, len, msdos_name, &sbi->options);
+	if (err)
+		return -ENOENT;
+
+	err = fat_scan(dir, msdos_name, sinfo);
+	if (!err && sbi->options.dotsOK) {
+		if (name[0] == '.') {
+			if (!(sinfo->de->attr & ATTR_HIDDEN))
+				err = -ENOENT;
+		} else {
+			if (sinfo->de->attr & ATTR_HIDDEN)
+				err = -ENOENT;
+		}
+		if (err)
+			brelse(sinfo->bh);
+	}
+	return err;
+}
+
+/*
+ * Compute the hash for the msdos name corresponding to the dentry.
+ * Note: if the name is invalid, we leave the hash code unchanged so
+ * that the existing dentry can be used. The msdos fs routines will
+ * return ENOENT or EINVAL as appropriate.
+ */
+static int msdos_hash(const struct dentry *dentry, struct qstr *qstr)
+{
+	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
+	unsigned char msdos_name[MSDOS_NAME];
+	int error;
+
+	error = msdos_format_name(qstr->name, qstr->len, msdos_name, options);
+	if (!error)
+		qstr->hash = full_name_hash(dentry, msdos_name, MSDOS_NAME);
+	return 0;
+}
+
+/*
+ * Compare two msdos names. If either of the names are invalid,
+ * we fall back to doing the standard name comparison.
+ */
+static int msdos_cmp(const struct dentry *dentry,
+		unsigned int len, const char *str, const struct qstr *name)
+{
+	struct fat_mount_options *options = &MSDOS_SB(dentry->d_sb)->options;
+	unsigned char a_msdos_name[MSDOS_NAME], b_msdos_name[MSDOS_NAME];
+	int error;
+
+	error = msdos_format_name(name->name, name->len, a_msdos_name, options);
+	if (error)
+		goto old_compare;
+	error = msdos_format_name(str, len, b_msdos_name, options);
+	if (error)
+		goto old_compare;
+	error = memcmp(a_msdos_name, b_msdos_name, MSDOS_NAME);
+out:
+	return error;
+
+old_compare:
+	error = 1;
+	if (name->len == len)
+		error = memcmp(name->name, str, len);
+	goto out;
+}
+
+static const struct dentry_operations msdos_dentry_operations = {
+	.d_hash		= msdos_hash,
+	.d_compare	= msdos_cmp,
+};
+
+/*
+ * AV. Wrappers for FAT sb operations. Is it wise?
+ */
+
+/***** Get inode using directory and name */
+static struct dentry *msdos_lookup(struct inode *dir, struct dentry *dentry,
+				   unsigned int flags)
+{
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	struct inode *inode;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
+	switch (err) {
+	case -ENOENT:
+		inode = NULL;
+		break;
+	case 0:
+		inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+		brelse(sinfo.bh);
+		break;
+	default:
+		inode = ERR_PTR(err);
+	}
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return d_splice_alias(inode, dentry);
+}
+
+/***** Creates a directory entry (name is already formatted). */
+static int msdos_add_entry(struct inode *dir, const unsigned char *name,
+			   int is_dir, int is_hid, int cluster,
+			   struct timespec64 *ts, struct fat_slot_info *sinfo)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(dir->i_sb);
+	struct msdos_dir_entry de;
+	__le16 time, date;
+	int err;
+
+	memcpy(de.name, name, MSDOS_NAME);
+	de.attr = is_dir ? ATTR_DIR : ATTR_ARCH;
+	if (is_hid)
+		de.attr |= ATTR_HIDDEN;
+	de.lcase = 0;
+	fat_time_unix2fat(sbi, ts, &time, &date, NULL);
+	de.cdate = de.adate = 0;
+	de.ctime = 0;
+	de.ctime_cs = 0;
+	de.time = time;
+	de.date = date;
+	fat_set_start(&de, cluster);
+	de.size = 0;
+
+	err = fat_add_entries(dir, &de, 1, sinfo);
+	if (err)
+		return err;
+
+	fat_truncate_time(dir, ts, FAT_UPDATE_CMTIME);
+	if (IS_DIRSYNC(dir))
+		(void)fat_sync_inode(dir);
+	else
+		mark_inode_dirty(dir);
+
+	return 0;
+}
+
+/***** Create a file */
+static int msdos_create(struct mnt_idmap *idmap, struct inode *dir,
+			struct dentry *dentry, umode_t mode, bool excl)
+{
+	struct super_block *sb = dir->i_sb;
+	struct inode *inode = NULL;
+	struct fat_slot_info sinfo;
+	struct timespec64 ts;
+	unsigned char msdos_name[MSDOS_NAME];
+	int err, is_hid;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
+				msdos_name, &MSDOS_SB(sb)->options);
+	if (err)
+		goto out;
+	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
+	/* Have to do it due to foo vs. .foo conflicts */
+	if (!fat_scan(dir, msdos_name, &sinfo)) {
+		brelse(sinfo.bh);
+		err = -EINVAL;
+		goto out;
+	}
+
+	ts = current_time(dir);
+	err = msdos_add_entry(dir, msdos_name, 0, is_hid, 0, &ts, &sinfo);
+	if (err)
+		goto out;
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		goto out;
+	}
+	fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
+	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
+
+	d_instantiate(dentry, inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, dir, inode);
+	return err;
+}
+
+/***** Remove a directory */
+static int msdos_rmdir(struct inode *dir, struct dentry *dentry)
+{
+	struct super_block *sb = dir->i_sb;
+	struct inode *inode = d_inode(dentry);
+	struct fat_slot_info sinfo;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = fat_dir_empty(inode);
+	if (err)
+		goto out;
+	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
+	if (err)
+		goto out;
+
+	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
+	if (err)
+		goto out;
+	if (dir->i_nlink >= 3)
+		drop_nlink(dir);
+	else {
+		fat_fs_error(sb, "parent dir link count too low (%u)",
+			dir->i_nlink);
+	}
+
+	clear_nlink(inode);
+	fat_detach(inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, dir, inode);
+
+	return err;
+}
+
+/***** Make a directory */
+static struct dentry *msdos_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+				  struct dentry *dentry, umode_t mode)
+{
+	struct super_block *sb = dir->i_sb;
+	struct fat_slot_info sinfo;
+	struct inode *inode;
+	unsigned char msdos_name[MSDOS_NAME];
+	struct timespec64 ts;
+	int err, is_hid, cluster;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = msdos_format_name(dentry->d_name.name, dentry->d_name.len,
+				msdos_name, &MSDOS_SB(sb)->options);
+	if (err)
+		goto out;
+	is_hid = (dentry->d_name.name[0] == '.') && (msdos_name[0] != '.');
+	/* foo vs .foo situation */
+	if (!fat_scan(dir, msdos_name, &sinfo)) {
+		brelse(sinfo.bh);
+		err = -EINVAL;
+		goto out;
+	}
+
+	ts = current_time(dir);
+	cluster = fat_alloc_new_dir(dir, &ts);
+	if (cluster < 0) {
+		err = cluster;
+		goto out;
+	}
+	err = msdos_add_entry(dir, msdos_name, 1, is_hid, cluster, &ts, &sinfo);
+	if (err)
+		goto out_free;
+	inc_nlink(dir);
+
+	inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+	brelse(sinfo.bh);
+	if (IS_ERR(inode)) {
+		err = PTR_ERR(inode);
+		/* the directory was completed, just return a error */
+		goto out;
+	}
+	set_nlink(inode, 2);
+	fat_truncate_time(inode, &ts, FAT_UPDATE_ATIME | FAT_UPDATE_CMTIME);
+	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
+
+	d_instantiate(dentry, inode);
+
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	fat_flush_inodes(sb, dir, inode);
+	return NULL;
+
+out_free:
+	fat_free_clusters(dir, cluster);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	return ERR_PTR(err);
+}
+
+/***** Unlink a file */
+static int msdos_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct inode *inode = d_inode(dentry);
+	struct super_block *sb = inode->i_sb;
+	struct fat_slot_info sinfo;
+	int err;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+	err = msdos_find(dir, dentry->d_name.name, dentry->d_name.len, &sinfo);
+	if (err)
+		goto out;
+
+	err = fat_remove_entries(dir, &sinfo);	/* and releases bh */
+	if (err)
+		goto out;
+	clear_nlink(inode);
+	fat_detach(inode);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, dir, inode);
+
+	return err;
+}
+
+static int do_msdos_rename(struct inode *old_dir, unsigned char *old_name,
+			   struct dentry *old_dentry,
+			   struct inode *new_dir, unsigned char *new_name,
+			   struct dentry *new_dentry, int is_hid)
+{
+	struct buffer_head *dotdot_bh;
+	struct msdos_dir_entry *dotdot_de;
+	struct inode *old_inode, *new_inode;
+	struct fat_slot_info old_sinfo, sinfo;
+	struct timespec64 ts;
+	loff_t new_i_pos;
+	int err, old_attrs, is_dir, update_dotdot, corrupt = 0;
+
+	old_sinfo.bh = sinfo.bh = dotdot_bh = NULL;
+	old_inode = d_inode(old_dentry);
+	new_inode = d_inode(new_dentry);
+
+	err = fat_scan(old_dir, old_name, &old_sinfo);
+	if (err) {
+		err = -EIO;
+		goto out;
+	}
+
+	is_dir = S_ISDIR(old_inode->i_mode);
+	update_dotdot = (is_dir && old_dir != new_dir);
+	if (update_dotdot) {
+		if (fat_get_dotdot_entry(old_inode, &dotdot_bh, &dotdot_de)) {
+			err = -EIO;
+			goto out;
+		}
+	}
+
+	old_attrs = MSDOS_I(old_inode)->i_attrs;
+	err = fat_scan(new_dir, new_name, &sinfo);
+	if (!err) {
+		if (!new_inode) {
+			/* "foo" -> ".foo" case. just change the ATTR_HIDDEN */
+			if (sinfo.de != old_sinfo.de) {
+				err = -EINVAL;
+				goto out;
+			}
+			if (is_hid)
+				MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
+			else
+				MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
+			if (IS_DIRSYNC(old_dir)) {
+				err = fat_sync_inode(old_inode);
+				if (err) {
+					MSDOS_I(old_inode)->i_attrs = old_attrs;
+					goto out;
+				}
+			} else
+				mark_inode_dirty(old_inode);
+
+			inode_inc_iversion(old_dir);
+			fat_truncate_time(old_dir, NULL, FAT_UPDATE_CMTIME);
+			if (IS_DIRSYNC(old_dir))
+				(void)fat_sync_inode(old_dir);
+			else
+				mark_inode_dirty(old_dir);
+			goto out;
+		}
+	}
+
+	ts = current_time(old_inode);
+	if (new_inode) {
+		if (err)
+			goto out;
+		if (is_dir) {
+			err = fat_dir_empty(new_inode);
+			if (err)
+				goto out;
+		}
+		new_i_pos = MSDOS_I(new_inode)->i_pos;
+		fat_detach(new_inode);
+	} else {
+		err = msdos_add_entry(new_dir, new_name, is_dir, is_hid, 0,
+				      &ts, &sinfo);
+		if (err)
+			goto out;
+		new_i_pos = sinfo.i_pos;
+	}
+	inode_inc_iversion(new_dir);
+
+	fat_detach(old_inode);
+	fat_attach(old_inode, new_i_pos);
+	if (is_hid)
+		MSDOS_I(old_inode)->i_attrs |= ATTR_HIDDEN;
+	else
+		MSDOS_I(old_inode)->i_attrs &= ~ATTR_HIDDEN;
+	if (IS_DIRSYNC(new_dir)) {
+		err = fat_sync_inode(old_inode);
+		if (err)
+			goto error_inode;
+	} else
+		mark_inode_dirty(old_inode);
+
+	if (update_dotdot) {
+		fat_set_start(dotdot_de, MSDOS_I(new_dir)->i_logstart);
+		mmb_mark_buffer_dirty(dotdot_bh,
+				      &MSDOS_I(old_inode)->i_metadata_bhs);
+		if (IS_DIRSYNC(new_dir)) {
+			err = sync_dirty_buffer(dotdot_bh);
+			if (err)
+				goto error_dotdot;
+		}
+		drop_nlink(old_dir);
+		if (!new_inode)
+			inc_nlink(new_dir);
+	}
+
+	err = fat_remove_entries(old_dir, &old_sinfo);	/* and releases bh */
+	old_sinfo.bh = NULL;
+	if (err)
+		goto error_dotdot;
+	inode_inc_iversion(old_dir);
+	fat_truncate_time(old_dir, &ts, FAT_UPDATE_CMTIME);
+	if (IS_DIRSYNC(old_dir))
+		(void)fat_sync_inode(old_dir);
+	else
+		mark_inode_dirty(old_dir);
+
+	if (new_inode) {
+		drop_nlink(new_inode);
+		if (is_dir)
+			drop_nlink(new_inode);
+	}
+out:
+	brelse(sinfo.bh);
+	brelse(dotdot_bh);
+	brelse(old_sinfo.bh);
+	return err;
+
+error_dotdot:
+	/* data cluster is shared, serious corruption */
+	corrupt = 1;
+
+	if (update_dotdot) {
+		fat_set_start(dotdot_de, MSDOS_I(old_dir)->i_logstart);
+		mmb_mark_buffer_dirty(dotdot_bh,
+				      &MSDOS_I(old_inode)->i_metadata_bhs);
+		corrupt |= sync_dirty_buffer(dotdot_bh);
+	}
+error_inode:
+	fat_detach(old_inode);
+	fat_attach(old_inode, old_sinfo.i_pos);
+	MSDOS_I(old_inode)->i_attrs = old_attrs;
+	if (new_inode) {
+		fat_attach(new_inode, new_i_pos);
+		if (corrupt)
+			corrupt |= fat_sync_inode(new_inode);
+	} else {
+		/*
+		 * If new entry was not sharing the data cluster, it
+		 * shouldn't be serious corruption.
+		 */
+		int err2 = fat_remove_entries(new_dir, &sinfo);
+		if (corrupt)
+			corrupt |= err2;
+		sinfo.bh = NULL;
+	}
+	if (corrupt < 0) {
+		fat_fs_error(new_dir->i_sb,
+			     "%s: Filesystem corrupted (i_pos %lld)",
+			     __func__, sinfo.i_pos);
+	}
+	goto out;
+}
+
+/***** Rename, a wrapper for rename_same_dir & rename_diff_dir */
+static int msdos_rename(struct mnt_idmap *idmap,
+			struct inode *old_dir, struct dentry *old_dentry,
+			struct inode *new_dir, struct dentry *new_dentry,
+			unsigned int flags)
+{
+	struct super_block *sb = old_dir->i_sb;
+	unsigned char old_msdos_name[MSDOS_NAME], new_msdos_name[MSDOS_NAME];
+	int err, is_hid;
+
+	if (flags & ~RENAME_NOREPLACE)
+		return -EINVAL;
+
+	mutex_lock(&MSDOS_SB(sb)->s_lock);
+
+	err = msdos_format_name(old_dentry->d_name.name,
+				old_dentry->d_name.len, old_msdos_name,
+				&MSDOS_SB(old_dir->i_sb)->options);
+	if (err)
+		goto out;
+	err = msdos_format_name(new_dentry->d_name.name,
+				new_dentry->d_name.len, new_msdos_name,
+				&MSDOS_SB(new_dir->i_sb)->options);
+	if (err)
+		goto out;
+
+	is_hid =
+	     (new_dentry->d_name.name[0] == '.') && (new_msdos_name[0] != '.');
+
+	err = do_msdos_rename(old_dir, old_msdos_name, old_dentry,
+			      new_dir, new_msdos_name, new_dentry, is_hid);
+out:
+	mutex_unlock(&MSDOS_SB(sb)->s_lock);
+	if (!err)
+		err = fat_flush_inodes(sb, old_dir, new_dir);
+	return err;
+}
+
+static const struct inode_operations msdos_dir_inode_operations = {
+	.create		= msdos_create,
+	.lookup		= msdos_lookup,
+	.unlink		= msdos_unlink,
+	.mkdir		= msdos_mkdir,
+	.rmdir		= msdos_rmdir,
+	.rename		= msdos_rename,
+	.setattr	= fat_setattr,
+	.getattr	= fat_getattr,
+	.fileattr_get	= fat_fileattr_get,
+	.update_time	= fat_update_time,
+};
+
+static void setup(struct super_block *sb)
+{
+	MSDOS_SB(sb)->dir_ops = &msdos_dir_inode_operations;
+	set_default_d_op(sb, &msdos_dentry_operations);
+	sb->s_flags |= SB_NOATIME;
+}
+
+static int msdos_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	return fat_fill_super(sb, fc, setup);
+}
+
+static int msdos_get_tree(struct fs_context *fc)
+{
+	return get_tree_bdev(fc, msdos_fill_super);
+}
+
+static int msdos_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	return fat_parse_param(fc, param, false);
+}
+
+static const struct fs_context_operations msdos_context_ops = {
+	.parse_param	= msdos_parse_param,
+	.get_tree	= msdos_get_tree,
+	.reconfigure	= fat_reconfigure,
+	.free		= fat_free_fc,
+};
+
+static int msdos_init_fs_context(struct fs_context *fc)
+{
+	int err;
+
+	/* Initialize with is_vfat == false */
+	err = fat_init_fs_context(fc, false);
+	if (err)
+		return err;
+
+	fc->ops = &msdos_context_ops;
+	return 0;
+}
+
+static struct file_system_type msdos_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "msdos",
+	.kill_sb	= kill_block_super,
+	.fs_flags	= FS_REQUIRES_DEV | FS_ALLOW_IDMAP,
+	.init_fs_context = msdos_init_fs_context,
+	.parameters	= fat_param_spec,
+};
+MODULE_ALIAS_FS("msdos");
+
+static int __init init_msdos_fs(void)
+{
+	return register_filesystem(&msdos_fs_type);
+}
+
+static void __exit exit_msdos_fs(void)
+{
+	unregister_filesystem(&msdos_fs_type);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Werner Almesberger");
+MODULE_DESCRIPTION("MS-DOS filesystem support");
+
+module_init(init_msdos_fs)
+module_exit(exit_msdos_fs)

linux-7.2.3/fs/fat/nfs.c

@@ -0,0 +1,299 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* fs/fat/nfs.c
+ */
+
+#include <linux/exportfs.h>
+#include "fat.h"
+
+struct fat_fid {
+	u32 i_gen;
+	u32 i_pos_low;
+	u16 i_pos_hi;
+	u16 parent_i_pos_hi;
+	u32 parent_i_pos_low;
+	u32 parent_i_gen;
+};
+
+#define FAT_FID_SIZE_WITHOUT_PARENT 3
+#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))
+
+/*
+ * Look up a directory inode given its starting cluster.
+ */
+static struct inode *fat_dget(struct super_block *sb, int i_logstart)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct hlist_head *head;
+	struct msdos_inode_info *i;
+	struct inode *inode = NULL;
+
+	head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
+	spin_lock(&sbi->dir_hash_lock);
+	hlist_for_each_entry(i, head, i_dir_hash) {
+		BUG_ON(i->vfs_inode.i_sb != sb);
+		if (i->i_logstart != i_logstart)
+			continue;
+		inode = igrab(&i->vfs_inode);
+		if (inode)
+			break;
+	}
+	spin_unlock(&sbi->dir_hash_lock);
+	return inode;
+}
+
+static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
+{
+	if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
+		return fat_iget(sb, i_pos);
+
+	else {
+		if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
+			return NULL;
+		return ilookup(sb, ino);
+	}
+}
+
+static struct inode *__fat_nfs_get_inode(struct super_block *sb,
+				       u64 ino, u32 generation, loff_t i_pos)
+{
+	struct inode *inode = fat_ilookup(sb, ino, i_pos);
+
+	if (inode && generation && (inode->i_generation != generation)) {
+		iput(inode);
+		inode = NULL;
+	}
+	if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
+		struct buffer_head *bh = NULL;
+		struct msdos_dir_entry *de ;
+		sector_t blocknr;
+		int offset;
+		fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset);
+		bh = sb_bread(sb, blocknr);
+		if (!bh) {
+			fat_msg(sb, KERN_ERR,
+				"unable to read block(%llu) for building NFS inode",
+				(llu)blocknr);
+			return inode;
+		}
+		de = (struct msdos_dir_entry *)bh->b_data;
+		/* If a file is deleted on server and client is not updated
+		 * yet, we must not build the inode upon a lookup call.
+		 */
+		if (IS_FREE(de[offset].name))
+			inode = NULL;
+		else
+			inode = fat_build_inode(sb, &de[offset], i_pos);
+		brelse(bh);
+	}
+
+	return inode;
+}
+
+static struct inode *fat_nfs_get_inode(struct super_block *sb,
+				       u64 ino, u32 generation)
+{
+
+	return __fat_nfs_get_inode(sb, ino, generation, 0);
+}
+
+static int
+fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
+		      struct inode *parent)
+{
+	int len = *lenp;
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	struct fat_fid *fid = (struct fat_fid *) fh;
+	loff_t i_pos;
+	int type = FILEID_FAT_WITHOUT_PARENT;
+
+	if (parent) {
+		if (len < FAT_FID_SIZE_WITH_PARENT) {
+			*lenp = FAT_FID_SIZE_WITH_PARENT;
+			return FILEID_INVALID;
+		}
+	} else {
+		if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
+			*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
+			return FILEID_INVALID;
+		}
+	}
+
+	i_pos = fat_i_pos_read(sbi, inode);
+	*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
+	fid->i_gen = inode->i_generation;
+	fid->i_pos_low = i_pos & 0xFFFFFFFF;
+	fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
+	if (parent) {
+		i_pos = fat_i_pos_read(sbi, parent);
+		fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
+		fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
+		fid->parent_i_gen = parent->i_generation;
+		type = FILEID_FAT_WITH_PARENT;
+		*lenp = FAT_FID_SIZE_WITH_PARENT;
+	} else {
+		/*
+		 * We need to initialize this field because the fh is actually
+		 * 12 bytes long
+		 */
+		fid->parent_i_pos_hi = 0;
+	}
+
+	return type;
+}
+
+/*
+ * Map a NFS file handle to a corresponding dentry.
+ * The dentry may or may not be connected to the filesystem root.
+ */
+static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
+				int fh_len, int fh_type)
+{
+	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
+				    fat_nfs_get_inode);
+}
+
+static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
+					       struct fid *fh, int fh_len,
+					       int fh_type)
+{
+	struct inode *inode = NULL;
+	struct fat_fid *fid = (struct fat_fid *)fh;
+	loff_t i_pos;
+
+	switch (fh_type) {
+	case FILEID_FAT_WITHOUT_PARENT:
+		if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
+			return NULL;
+		break;
+	case FILEID_FAT_WITH_PARENT:
+		if (fh_len < FAT_FID_SIZE_WITH_PARENT)
+			return NULL;
+		break;
+	default:
+		return NULL;
+	}
+	i_pos = fid->i_pos_hi;
+	i_pos = (i_pos << 32) | (fid->i_pos_low);
+	inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);
+
+	return d_obtain_alias(inode);
+}
+
+/*
+ * Find the parent for a file specified by NFS handle.
+ * This requires that the handle contain the i_ino of the parent.
+ */
+static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
+				int fh_len, int fh_type)
+{
+	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
+				    fat_nfs_get_inode);
+}
+
+static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
+					       struct fid *fh, int fh_len,
+					       int fh_type)
+{
+	struct inode *inode = NULL;
+	struct fat_fid *fid = (struct fat_fid *)fh;
+	loff_t i_pos;
+
+	if (fh_len < FAT_FID_SIZE_WITH_PARENT)
+		return NULL;
+
+	switch (fh_type) {
+	case FILEID_FAT_WITH_PARENT:
+		i_pos = fid->parent_i_pos_hi;
+		i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
+		inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos);
+		break;
+	}
+
+	return d_obtain_alias(inode);
+}
+
+/*
+ * Rebuild the parent for a directory that is not connected
+ *  to the filesystem root
+ */
+static
+struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
+{
+	int search_clus, clus_to_match;
+	struct msdos_dir_entry *de;
+	struct inode *parent = NULL;
+	struct inode *dummy_grand_parent = NULL;
+	struct fat_slot_info sinfo;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart);
+	struct buffer_head *parent_bh = sb_bread(sb, blknr);
+	if (!parent_bh) {
+		fat_msg(sb, KERN_ERR,
+			"unable to read cluster of parent directory");
+		return NULL;
+	}
+
+	de = (struct msdos_dir_entry *) parent_bh->b_data;
+	clus_to_match = fat_get_start(sbi, &de[0]);
+	search_clus = fat_get_start(sbi, &de[1]);
+
+	dummy_grand_parent = fat_dget(sb, search_clus);
+	if (!dummy_grand_parent) {
+		dummy_grand_parent = new_inode(sb);
+		if (!dummy_grand_parent) {
+			brelse(parent_bh);
+			return parent;
+		}
+
+		dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
+		fat_fill_inode(dummy_grand_parent, &de[1]);
+		MSDOS_I(dummy_grand_parent)->i_pos = -1;
+	}
+
+	if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo))
+		parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
+
+	brelse(parent_bh);
+	iput(dummy_grand_parent);
+
+	return parent;
+}
+
+/*
+ * Find the parent for a directory that is not currently connected to
+ * the filesystem root.
+ *
+ * On entry, the caller holds d_inode(child_dir)->i_mutex.
+ */
+static struct dentry *fat_get_parent(struct dentry *child_dir)
+{
+	struct super_block *sb = child_dir->d_sb;
+	struct buffer_head *bh = NULL;
+	struct msdos_dir_entry *de;
+	struct inode *parent_inode = NULL;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (!fat_get_dotdot_entry(d_inode(child_dir), &bh, &de)) {
+		int parent_logstart = fat_get_start(sbi, de);
+		parent_inode = fat_dget(sb, parent_logstart);
+		if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
+			parent_inode = fat_rebuild_parent(sb, parent_logstart);
+	}
+	brelse(bh);
+
+	return d_obtain_alias(parent_inode);
+}
+
+const struct export_operations fat_export_ops = {
+	.encode_fh	= generic_encode_ino32_fh,
+	.fh_to_dentry   = fat_fh_to_dentry,
+	.fh_to_parent   = fat_fh_to_parent,
+	.get_parent     = fat_get_parent,
+};
+
+const struct export_operations fat_export_ops_nostale = {
+	.encode_fh      = fat_encode_fh_nostale,
+	.fh_to_dentry   = fat_fh_to_dentry_nostale,
+	.fh_to_parent   = fat_fh_to_parent_nostale,
+	.get_parent     = fat_get_parent,
+};