vfs: check bh->b_blocknr only if BH_Mapped is set
Nikanth Karthikesan [Thu, 2 Apr 2009 23:56:46 +0000 (16:56 -0700)]
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>

fs/buffer.c

index f5f8b15..2963858 100644 (file)
@@ -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);