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 <[email protected]>
Cc: Nick Piggin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/fs/buffer.c b/fs/buffer.c
index f5f8b15a6e4087f947a2101a46f0855048bca6f0..2963858f0f31f106b878966c75ca09991c7486f7 100644 (file)
--- 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);