fat: mark fs as dirty on mount and clean on umount

There is no documented methods to mark FAT as dirty. Unofficially MS started to use reserved Byte in boot sector for this purpose, at least since Win 2000. With Win 7 user is warned if fs is dirty and asked to clean it. Different versions of Win, handle it in different ways, but always have same meaning: - Win 2000 and XP, set it on write operations and remove it after operation was finnished - Win 7, set dirty flag on first write and remove it on umount. We will do it as follows: - set dirty flag on mount. If fs was initially dirty, warn user, remember it and do not do any changes to boot sector. - clean it on umount. If fs was initially dirty, leave it dirty. - do not do any thing if fs mounted read-only. - TODO: leave fs dirty if we found some error after mount. Signed-off-by: Oleksij Rempel <bug-track@fisher-privat.net> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fat: mark fs as dirty on mount and clean on umount
There is no documented methods to mark FAT as dirty. Unofficially MS started to use reserved Byte in boot sector for this purpose, at least since Win 2000. With Win 7 user is warned if fs is dirty and asked to clean it. Different versions of Win, handle it in different ways, but always have same meaning: - Win 2000 and XP, set it on write operations and remove it after operation was finnished - Win 7, set dirty flag on first write and remove it on umount. We will do it as follows: - set dirty flag on mount. If fs was initially dirty, warn user, remember it and do not do any changes to boot sector. - clean it on umount. If fs was initially dirty, leave it dirty. - do not do any thing if fs mounted read-only. - TODO: leave fs dirty if we found some error after mount. Signed-off-by: Oleksij Rempel <bug-track@fisher-privat.net> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Oleksij Rempel · Linus Torvalds
1 parent 6b46419b04
Showing 3 changed files with 70 additions and 0 deletions Side-by-side Diff
fs/fat/fat.h
fs/fat/inode.c
include/uapi/linux/msdos_fs.h
@@ -95,6 +95,8 @@
  
 	spinlock_t dir_hash_lock;
 	struct hlist_head dir_hashtable[FAT_HASH_SIZE];
+
+	unsigned int dirty;           /* fs state before mount */
 };
  
 #define FAT_CACHE_VALID	0	/* special case for valid cache */
@@ -488,10 +488,59 @@
 	fat_detach(inode);
 }
  
+static void fat_set_state(struct super_block *sb,
+			unsigned int set, unsigned int force)
+{
+	struct buffer_head *bh;
+	struct fat_boot_sector *b;
+	struct msdos_sb_info *sbi = sb->s_fs_info;
+
+	/* do not change any thing if mounted read only */
+	if ((sb->s_flags & MS_RDONLY) && !force)
+		return;
+
+	/* do not change state if fs was dirty */
+	if (sbi->dirty) {
+		/* warn only on set (mount). */
+		if (set)
+			fat_msg(sb, KERN_WARNING, "Volume was not properly "
+				"unmounted. Some data may be corrupt. "
+				"Please run fsck.");
+		return;
+	}
+
+	bh = sb_bread(sb, 0);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR, "unable to read boot sector "
+			"to mark fs as dirty");
+		return;
+	}
+
+	b = (struct fat_boot_sector *) bh->b_data;
+
+	if (sbi->fat_bits == 32) {
+		if (set)
+			b->fat32.state |= FAT_STATE_DIRTY;
+		else
+			b->fat32.state &= ~FAT_STATE_DIRTY;
+	} else /* fat 16 and 12 */ {
+		if (set)
+			b->fat16.state |= FAT_STATE_DIRTY;
+		else
+			b->fat16.state &= ~FAT_STATE_DIRTY;
+	}
+
+	mark_buffer_dirty(bh);
+	sync_dirty_buffer(bh);
+	brelse(bh);
+}
+
 static void fat_put_super(struct super_block *sb)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
  
+	fat_set_state(sb, 0, 0);
+
 	iput(sbi->fsinfo_inode);
 	iput(sbi->fat_inode);
  
  
@@ -566,8 +615,18 @@
  
 static int fat_remount(struct super_block *sb, int *flags, char *data)
 {
+	int new_rdonly;
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 	*flags |= MS_NODIRATIME | (sbi->options.isvfat ? 0 : MS_NOATIME);
+
+	/* make sure we update state on remount. */
+	new_rdonly = *flags & MS_RDONLY;
+	if (new_rdonly != (sb->s_flags & MS_RDONLY)) {
+		if (new_rdonly)
+			fat_set_state(sb, 0, 0);
+		else
+			fat_set_state(sb, 1, 1);
+	}
 	return 0;
 }
  
@@ -1362,6 +1421,12 @@
 	if (sbi->fat_bits != 32)
 		sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
  
+	/* some OSes set FAT_STATE_DIRTY and clean it on unmount. */
+	if (sbi->fat_bits == 32)
+		sbi->dirty = b->fat32.state & FAT_STATE_DIRTY;
+	else /* fat 16 or 12 */
+		sbi->dirty = b->fat16.state & FAT_STATE_DIRTY;
+
 	/* check that FAT table does not overflow */
 	fat_clusters = sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
 	total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
@@ -1456,6 +1521,7 @@
 					"the device does not support discard");
 	}
  
+	fat_set_state(sb, 1, 0);
 	return 0;
  
 out_invalid:
@@ -87,6 +87,8 @@
 #define IS_FSINFO(x)	(le32_to_cpu((x)->signature1) == FAT_FSINFO_SIG1 \
 			 && le32_to_cpu((x)->signature2) == FAT_FSINFO_SIG2)
  
+#define FAT_STATE_DIRTY 0x01
+
 struct __fat_dirent {
 	long		d_ino;
 	__kernel_off_t	d_off;
...	...	@@ -95,6 +95,8 @@
95	95
96	96	spinlock_t dir_hash_lock;
97	97	struct hlist_head dir_hashtable[FAT_HASH_SIZE];
	98	+
	99	+ unsigned int dirty; /* fs state before mount */
98	100	};
99	101
100	102	#define FAT_CACHE_VALID 0 /* special case for valid cache */
...	...	@@ -488,10 +488,59 @@
488	488	fat_detach(inode);
489	489	}
490	490
	491	+static void fat_set_state(struct super_block *sb,
	492	+ unsigned int set, unsigned int force)
	493	+{
	494	+ struct buffer_head *bh;
	495	+ struct fat_boot_sector *b;
	496	+ struct msdos_sb_info *sbi = sb->s_fs_info;
	497	+
	498	+ /* do not change any thing if mounted read only */
	499	+ if ((sb->s_flags & MS_RDONLY) && !force)
	500	+ return;
	501	+
	502	+ /* do not change state if fs was dirty */
	503	+ if (sbi->dirty) {
	504	+ /* warn only on set (mount). */
	505	+ if (set)
	506	+ fat_msg(sb, KERN_WARNING, "Volume was not properly "
	507	+ "unmounted. Some data may be corrupt. "
	508	+ "Please run fsck.");
	509	+ return;
	510	+ }
	511	+
	512	+ bh = sb_bread(sb, 0);
	513	+ if (bh == NULL) {
	514	+ fat_msg(sb, KERN_ERR, "unable to read boot sector "
	515	+ "to mark fs as dirty");
	516	+ return;
	517	+ }
	518	+
	519	+ b = (struct fat_boot_sector *) bh->b_data;
	520	+
	521	+ if (sbi->fat_bits == 32) {
	522	+ if (set)
	523	+ b->fat32.state \|= FAT_STATE_DIRTY;
	524	+ else
	525	+ b->fat32.state &= ~FAT_STATE_DIRTY;
	526	+ } else /* fat 16 and 12 */ {
	527	+ if (set)
	528	+ b->fat16.state \|= FAT_STATE_DIRTY;
	529	+ else
	530	+ b->fat16.state &= ~FAT_STATE_DIRTY;
	531	+ }
	532	+
	533	+ mark_buffer_dirty(bh);
	534	+ sync_dirty_buffer(bh);
	535	+ brelse(bh);
	536	+}
	537	+
491	538	static void fat_put_super(struct super_block *sb)
492	539	{
493	540	struct msdos_sb_info *sbi = MSDOS_SB(sb);
494	541
	542	+ fat_set_state(sb, 0, 0);
	543	+
495	544	iput(sbi->fsinfo_inode);
496	545	iput(sbi->fat_inode);
497	546
498	547
...	...	@@ -566,8 +615,18 @@
566	615
567	616	static int fat_remount(struct super_block sb, int flags, char *data)
568	617	{
	618	+ int new_rdonly;
569	619	struct msdos_sb_info *sbi = MSDOS_SB(sb);
570	620	*flags \|= MS_NODIRATIME \| (sbi->options.isvfat ? 0 : MS_NOATIME);
	621	+
	622	+ /* make sure we update state on remount. */
	623	+ new_rdonly = *flags & MS_RDONLY;
	624	+ if (new_rdonly != (sb->s_flags & MS_RDONLY)) {
	625	+ if (new_rdonly)
	626	+ fat_set_state(sb, 0, 0);
	627	+ else
	628	+ fat_set_state(sb, 1, 1);
	629	+ }
571	630	return 0;
572	631	}
573	632
...	...	@@ -1362,6 +1421,12 @@
1362	1421	if (sbi->fat_bits != 32)
1363	1422	sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
1364	1423
	1424	+ /* some OSes set FAT_STATE_DIRTY and clean it on unmount. */
	1425	+ if (sbi->fat_bits == 32)
	1426	+ sbi->dirty = b->fat32.state & FAT_STATE_DIRTY;
	1427	+ else /* fat 16 or 12 */
	1428	+ sbi->dirty = b->fat16.state & FAT_STATE_DIRTY;
	1429	+
1365	1430	/* check that FAT table does not overflow */
1366	1431	fat_clusters = sbi->fat_length * sb->s_blocksize * 8 / sbi->fat_bits;
1367	1432	total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
...	...	@@ -1456,6 +1521,7 @@
1456	1521	"the device does not support discard");
1457	1522	}
1458	1523
	1524	+ fat_set_state(sb, 1, 0);
1459	1525	return 0;
1460	1526
1461	1527	out_invalid:
...	...	@@ -87,6 +87,8 @@
87	87	#define IS_FSINFO(x) (le32_to_cpu((x)->signature1) == FAT_FSINFO_SIG1 \
88	88	&& le32_to_cpu((x)->signature2) == FAT_FSINFO_SIG2)
89	89
	90	+#define FAT_STATE_DIRTY 0x01
	91	+
90	92	struct __fat_dirent {
91	93	long d_ino;
92	94	__kernel_off_t d_off;