libxfs: dirty buffers should be marked uptodate too

I started fuzz-testing the realtime rmap feature with a very large
number of realtime allocation groups.  There were so many rt groups that
repair had to rebuild /realtime in the metadata directory tree, and that
directory was big enough to spur the creation of a block format
directory.

Unfortunately, repair then walks both directory trees to look for
unconnceted files.  This part of phase 6 emits CRC errors on the newly
created buffers for the /realtime directory, declares the directory to
be garbage, and moves all the rt rmap inodes to /lost+found, resulting
in a corrupt fs.

Poking around in gdb, I noticed that the buffer contents were indeed
zero, and that UPTODATE was not set.  This was very strange, until I
added a watch on bp->b_flags to watch for accesses.  It turns out that
xfs_repair's prefetch code will _get a buffer and zero the contents if
UPTODATE is not set.

The directory tree code in libxfs will also _get a buffer, initialize
it, and log it to the coordinating transaction, which in this case is
the transactions used to reconnect the rmap btree inodes to /realtime.
At no point does any of that code ever set UPTODATE on the buffer, which
is why prefetch zaps the contents.

Hence change both buffer dirtying functions to set UPTODATE, since a
dirty buffer is by definition at least as recent as whatever's on disk.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index 0a87e5b6da9fab4af354394b01ecba44f83e4d0d..e430416f6f8f8462262106fbf961ae656363de50 100644 (file)
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -902,7 +902,7 @@ libxfs_buf_mark_dirty(
         */
        bp->b_error = 0;
        bp->b_flags &= ~LIBXFS_B_STALE;
-       bp->b_flags |= LIBXFS_B_DIRTY;
+       bp->b_flags |= LIBXFS_B_DIRTY | LIBXFS_B_UPTODATE;
 }
 
 /* Prepare a buffer to be sent to the MRU list. */

diff --git a/libxfs/trans.c b/libxfs/trans.c
index 7fec2caff4935686777f68939b50bacf7ef94ed0..7e36205c6a3d50bda4fcb051f8c55d988add9234 100644 (file)
--- a/libxfs/trans.c
+++ b/libxfs/trans.c
@@ -687,6 +687,7 @@ libxfs_trans_dirty_buf(
        ASSERT(bp->b_transp == tp);
        ASSERT(bip != NULL);
 
+       bp->b_flags |= LIBXFS_B_UPTODATE;
        tp->t_flags |= XFS_TRANS_DIRTY;
        set_bit(XFS_LI_DIRTY, &bip->bli_item.li_flags);
 }