UBIFS: introduce new flags for RO mounts

Commit 2fde99cb55fb9d9b88180512a5e8a5d939d27fec "UBIFS: mark VFS SB RO too"
introduced regression. This commit made UBIFS set the 'MS_RDONLY' flag in the
VFS superblock when it switches to R/O mode due to an error. This was done
to make VFS show the R/O UBIFS flag in /proc/mounts.

However, several places in UBIFS relied on the 'MS_RDONLY' flag and assume this
flag can only change when we re-mount. For example, 'ubifs_put_super()'.

This patch introduces new UBIFS flag - 'c->ro_mount' which changes only when
we re-mount, and preserves the way UBIFS was originally mounted (R/W or R/O).
This allows us to de-initialize UBIFS cleanly in 'ubifs_put_super()'.

This patch also changes all 'ubifs_assert(!c->ro_media)' assertions to
'ubifs_assert(!c->ro_media && !c->ro_mount)', because we never should write
anything if the FS was mounter R/O.

All the places where we test for 'MS_RDONLY' flag in the VFS SB were changed
and now we test the 'c->ro_mount' flag instead, because it preserves the
original UBIFS mount type, unlike the 'MS_RDONLY' flag.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 29 insertions, 26 deletions

diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 1cfeec5..4e5bf3f 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -1137,11 +1137,11 @@ static int check_free_space(struct ubifs_info *c)
  */
 static int mount_ubifs(struct ubifs_info *c)
 {
-	struct super_block *sb = c->vfs_sb;
-	int err, mounted_read_only = (sb->s_flags & MS_RDONLY);
+	int err;
 	long long x;
 	size_t sz;
 
+	c->ro_mount = !!(c->vfs_sb->s_flags & MS_RDONLY);
 	err = init_constants_early(c);
 	if (err)
 		return err;
@@ -1154,7 +1154,7 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (err)
 		goto out_free;
 
-	if (c->empty && (mounted_read_only || c->ro_media)) {
+	if (c->empty && (c->ro_mount || c->ro_media)) {
 		/*
 		 * This UBI volume is empty, and read-only, or the file system
 		 * is mounted read-only - we cannot format it.
@@ -1165,7 +1165,7 @@ static int mount_ubifs(struct ubifs_info *c)
 		goto out_free;
 	}
 
-	if (c->ro_media && !mounted_read_only) {
+	if (c->ro_media && !c->ro_mount) {
 		ubifs_err("cannot mount read-write - read-only media");
 		err = -EROFS;
 		goto out_free;
@@ -1185,7 +1185,7 @@ static int mount_ubifs(struct ubifs_info *c)
 	if (!c->sbuf)
 		goto out_free;
 
-	if (!mounted_read_only) {
+	if (!c->ro_mount) {
 		c->ileb_buf = vmalloc(c->leb_size);
 		if (!c->ileb_buf)
 			goto out_free;
@@ -1228,7 +1228,7 @@ static int mount_ubifs(struct ubifs_info *c)
 	}
 
 	sprintf(c->bgt_name, BGT_NAME_PATTERN, c->vi.ubi_num, c->vi.vol_id);
-	if (!mounted_read_only) {
+	if (!c->ro_mount) {
 		err = alloc_wbufs(c);
 		if (err)
 			goto out_cbuf;
@@ -1254,12 +1254,12 @@ static int mount_ubifs(struct ubifs_info *c)
 	if ((c->mst_node->flags & cpu_to_le32(UBIFS_MST_DIRTY)) != 0) {
 		ubifs_msg("recovery needed");
 		c->need_recovery = 1;
-		if (!mounted_read_only) {
+		if (!c->ro_mount) {
 			err = ubifs_recover_inl_heads(c, c->sbuf);
 			if (err)
 				goto out_master;
 		}
-	} else if (!mounted_read_only) {
+	} else if (!c->ro_mount) {
 		/*
 		 * Set the "dirty" flag so that if we reboot uncleanly we
 		 * will notice this immediately on the next mount.
@@ -1270,7 +1270,7 @@ static int mount_ubifs(struct ubifs_info *c)
 			goto out_master;
 	}
 
-	err = ubifs_lpt_init(c, 1, !mounted_read_only);
+	err = ubifs_lpt_init(c, 1, !c->ro_mount);
 	if (err)
 		goto out_lpt;
 
@@ -1285,11 +1285,11 @@ static int mount_ubifs(struct ubifs_info *c)
 	/* Calculate 'min_idx_lebs' after journal replay */
 	c->min_idx_lebs = ubifs_calc_min_idx_lebs(c);
 
-	err = ubifs_mount_orphans(c, c->need_recovery, mounted_read_only);
+	err = ubifs_mount_orphans(c, c->need_recovery, c->ro_mount);
 	if (err)
 		goto out_orphans;
 
-	if (!mounted_read_only) {
+	if (!c->ro_mount) {
 		int lnum;
 
 		err = check_free_space(c);
@@ -1351,7 +1351,7 @@ static int mount_ubifs(struct ubifs_info *c)
 	spin_unlock(&ubifs_infos_lock);
 
 	if (c->need_recovery) {
-		if (mounted_read_only)
+		if (c->ro_mount)
 			ubifs_msg("recovery deferred");
 		else {
 			c->need_recovery = 0;
@@ -1378,7 +1378,7 @@ static int mount_ubifs(struct ubifs_info *c)
 
 	ubifs_msg("mounted UBI device %d, volume %d, name \"%s\"",
 		  c->vi.ubi_num, c->vi.vol_id, c->vi.name);
-	if (mounted_read_only)
+	if (c->ro_mount)
 		ubifs_msg("mounted read-only");
 	x = (long long)c->main_lebs * c->leb_size;
 	ubifs_msg("file system size:   %lld bytes (%lld KiB, %lld MiB, %d "
@@ -1640,7 +1640,7 @@ static int ubifs_remount_rw(struct ubifs_info *c)
 	}
 
 	dbg_gen("re-mounted read-write");
-	c->vfs_sb->s_flags &= ~MS_RDONLY;
+	c->ro_mount = 0;
 	c->remounting_rw = 0;
 	c->always_chk_crc = 0;
 	err = dbg_check_space_info(c);
@@ -1676,7 +1676,7 @@ static void ubifs_remount_ro(struct ubifs_info *c)
 	int i, err;
 
 	ubifs_assert(!c->need_recovery);
-	ubifs_assert(!(c->vfs_sb->s_flags & MS_RDONLY));
+	ubifs_assert(!c->ro_mount);
 
 	mutex_lock(&c->umount_mutex);
 	if (c->bgt) {
@@ -1704,6 +1704,7 @@ static void ubifs_remount_ro(struct ubifs_info *c)
 	vfree(c->ileb_buf);
 	c->ileb_buf = NULL;
 	ubifs_lpt_free(c, 1);
+	c->ro_mount = 1;
 	err = dbg_check_space_info(c);
 	if (err)
 		ubifs_ro_mode(c, err);
@@ -1735,7 +1736,7 @@ static void ubifs_put_super(struct super_block *sb)
 	 * the mutex is locked.
 	 */
 	mutex_lock(&c->umount_mutex);
-	if (!(c->vfs_sb->s_flags & MS_RDONLY)) {
+	if (!c->ro_mount) {
 		/*
 		 * First of all kill the background thread to make sure it does
 		 * not interfere with un-mounting and freeing resources.
@@ -1745,23 +1746,23 @@ static void ubifs_put_super(struct super_block *sb)
 			c->bgt = NULL;
 		}
 
-		/* Synchronize write-buffers */
-		if (c->jheads)
-			for (i = 0; i < c->jhead_cnt; i++)
-				ubifs_wbuf_sync(&c->jheads[i].wbuf);
-
 		/*
 		 * On fatal errors c->ro_error is set to 1, in which case we do
 		 * not write the master node.
 		 */
 		if (!c->ro_error) {
+			int err;
+
+			/* Synchronize write-buffers */
+			if (c->jheads)
+				for (i = 0; i < c->jhead_cnt; i++)
+					ubifs_wbuf_sync(&c->jheads[i].wbuf);
+
 			/*
 			 * We are being cleanly unmounted which means the
 			 * orphans were killed - indicate this in the master
 			 * node. Also save the reserved GC LEB number.
 			 */
-			int err;
-
 			c->mst_node->flags &= ~cpu_to_le32(UBIFS_MST_DIRTY);
 			c->mst_node->flags |= cpu_to_le32(UBIFS_MST_NO_ORPHS);
 			c->mst_node->gc_lnum = cpu_to_le32(c->gc_lnum);
@@ -1797,7 +1798,7 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 		return err;
 	}
 
-	if ((sb->s_flags & MS_RDONLY) && !(*flags & MS_RDONLY)) {
+	if (c->ro_mount && !(*flags & MS_RDONLY)) {
 		if (c->ro_error) {
 			ubifs_msg("cannot re-mount R/W due to prior errors");
 			return -EROFS;
@@ -1809,7 +1810,7 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
 		err = ubifs_remount_rw(c);
 		if (err)
 			return err;
-	} else if (!(sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY)) {
+	} else if (!c->ro_mount && (*flags & MS_RDONLY)) {
 		if (c->ro_error) {
 			ubifs_msg("cannot re-mount R/O due to prior errors");
 			return -EROFS;
@@ -2068,9 +2069,11 @@ static int ubifs_get_sb(struct file_system_type *fs_type, int flags,
 	}
 
 	if (sb->s_root) {
+		struct ubifs_info *c1 = sb->s_fs_info;
+
 		/* A new mount point for already mounted UBIFS */
 		dbg_gen("this ubi volume is already mounted");
-		if ((flags ^ sb->s_flags) & MS_RDONLY) {
+		if (!!(flags & MS_RDONLY) != c1->ro_mount) {
 			err = -EBUSY;
 			goto out_deact;
 		}