vfs: check bh->b_blocknr only if BH_Mapped is set

Check bh->b_blocknr only if BH_Mapped is set.

akpm: I doubt if b_blocknr is ever uninitialised here, but it could
conceivably cause a problem if we're doing a lookup for block zero.

Signed-off-by: Nikanth Karthikesan <knikanth@suse.de>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index f5f8b15a6e40..2963858f0f31 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -199,13 +199,13 @@ __find_get_block_slow(struct block_device *bdev, sector_t block)
         head = page_buffers(page);
         bh = head;
         do {
-                if (bh->b_blocknr == block) {
+                if (!buffer_mapped(bh))
+                        all_mapped = 0;
+                else if (bh->b_blocknr == block) {
                         ret = bh;
                         get_bh(bh);
                         goto out_unlock;
                 }
-                if (!buffer_mapped(bh))
-                        all_mapped = 0;
                 bh = bh->b_this_page;
         } while (bh != head);