fs/ufs/super.c: fix potential race condition

Let locking subsystem decide on mutex management.  As reported by Andrew
Morton this patch fixes a bug:

: lock_ufs() is assuming that on non-preempt uniprocessor, the calling
: code will run atomically up to the matching unlock_ufs().
:
: But that isn't true. The very first site I looked at (ufs_frag_map)
: does sb_bread() under lock_ufs().  And sb_bread() will call schedule(),
: very commonly.
:
: The ->mutex_owner stuff is a bit hacky but should work OK.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/ufs/super.c b/fs/ufs/super.c
index e515e99..8092d37 100644 (file)
--- a/fs/ufs/super.c
+++ b/fs/ufs/super.c
@@ -95,22 +95,18 @@
 
 void lock_ufs(struct super_block *sb)
 {
-#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
        struct ufs_sb_info *sbi = UFS_SB(sb);
 
        mutex_lock(&sbi->mutex);
        sbi->mutex_owner = current;
-#endif
 }
 
 void unlock_ufs(struct super_block *sb)
 {
-#if defined(CONFIG_SMP) || defined (CONFIG_PREEMPT)
        struct ufs_sb_info *sbi = UFS_SB(sb);
 
        sbi->mutex_owner = NULL;
        mutex_unlock(&sbi->mutex);
-#endif
 }
 
 static struct inode *ufs_nfs_get_inode(struct super_block *sb, u64 ino, u32 generation)