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>

1 files changed, 9 insertions, 12 deletions

diff --git a/fs/reiserfs/super.c b/fs/reiserfs/super.c
index 1b52daa351c5..3da0401c0a96 100644
--- a/fs/reiserfs/super.c
+++ b/fs/reiserfs/super.c
@@ -64,18 +64,15 @@ static int reiserfs_statfs(struct dentry *dentry, struct kstatfs *buf);
 
 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;
 }