enforce ->sync_fs is only called for rw superblock
Make sure a superblock really is writeable by checking MS_RDONLY
under s_umount. sync_filesystems needed some re-arragement for
that, but all but one sync_filesystem caller had the correct locking
already so that we could add that check there. cachefiles grew
s_umount locking.
I've also added a WARN_ON to sync_filesystem to assert this for
future callers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 52d8452..9f179d4 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -394,9 +394,6 @@
struct btrfs_root *root = btrfs_sb(sb);
int ret;
- if (sb->s_flags & MS_RDONLY)
- return 0;
-
if (!wait) {
filemap_flush(root->fs_info->btree_inode->i_mapping);
return 0;
diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index dafd484..431accd 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -354,7 +354,9 @@
/* make sure all pages pinned by operations on behalf of the netfs are
* written to disc */
cachefiles_begin_secure(cache, &saved_cred);
+ down_read(&cache->mnt->mnt_sb->s_umount);
ret = sync_filesystem(cache->mnt->mnt_sb);
+ up_read(&cache->mnt->mnt_sb->s_umount);
cachefiles_end_secure(cache, saved_cred);
if (ret == -EIO)
diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index 1b52daa..3da0401 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -64,18 +64,15 @@
static int reiserfs_sync_fs(struct super_block *s, int wait)
{
- if (!(s->s_flags & MS_RDONLY)) {
- struct reiserfs_transaction_handle th;
- reiserfs_write_lock(s);
- if (!journal_begin(&th, s, 1))
- if (!journal_end_sync(&th, s, 1))
- reiserfs_flush_old_commits(s);
- s->s_dirt = 0; /* Even if it's not true.
- * We'll loop forever in sync_supers otherwise */
- reiserfs_write_unlock(s);
- } else {
- s->s_dirt = 0;
- }
+ struct reiserfs_transaction_handle th;
+
+ reiserfs_write_lock(s);
+ if (!journal_begin(&th, s, 1))
+ if (!journal_end_sync(&th, s, 1))
+ reiserfs_flush_old_commits(s);
+ s->s_dirt = 0; /* Even if it's not true.
+ * We'll loop forever in sync_supers otherwise */
+ reiserfs_write_unlock(s);
return 0;
}
diff --git a/fs/sync.c b/fs/sync.c
index 4487b55..89c37f7 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -51,6 +51,18 @@
{
int ret;
+ /*
+ * We need to be protected against the filesystem going from
+ * r/o to r/w or vice versa.
+ */
+ WARN_ON(!rwsem_is_locked(&sb->s_umount));
+
+ /*
+ * No point in syncing out anything if the filesystem is read-only.
+ */
+ if (sb->s_flags & MS_RDONLY)
+ return 0;
+
ret = __sync_filesystem(sb, 0);
if (ret < 0)
return ret;
@@ -79,25 +91,22 @@
mutex_lock(&mutex); /* Could be down_interruptible */
spin_lock(&sb_lock);
- list_for_each_entry(sb, &super_blocks, s_list) {
- if (sb->s_flags & MS_RDONLY)
- continue;
+ list_for_each_entry(sb, &super_blocks, s_list)
sb->s_need_sync = 1;
- }
restart:
list_for_each_entry(sb, &super_blocks, s_list) {
if (!sb->s_need_sync)
continue;
sb->s_need_sync = 0;
- if (sb->s_flags & MS_RDONLY)
- continue; /* hm. Was remounted r/o meanwhile */
sb->s_count++;
spin_unlock(&sb_lock);
+
down_read(&sb->s_umount);
- if (sb->s_root)
+ if (!(sb->s_flags & MS_RDONLY) && sb->s_root)
__sync_filesystem(sb, wait);
up_read(&sb->s_umount);
+
/* restart only when sb is no longer on the list */
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index e9f7a75..84f3c7f 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -447,9 +447,6 @@
if (!wait)
return 0;
- if (sb->s_flags & MS_RDONLY)
- return 0;
-
/*
* VFS calls '->sync_fs()' before synchronizing all dirty inodes and
* pages, so synchronize them first, then commit the journal. Strictly