On 11/22/18 12:13 PM, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> In process_node_dir2, we need to distinguish between a directory with a
> single leafn block (yes, they exist) having no interior da nodes, and a
> directory with a da tree that incorrectly points to dablk 0. If we
> happened to fill out any part of the da cursor then we have a da btree
> with garbage in it; otherwise, we have a single leafn block.
>
> This was found by repair repeatedly rebuilding a directory containing a
> single leafn block (xfs/495).
>
> Fixes: 67a79e2cc932 ("xfs_repair: treat zero da btree pointers as corruption")
> Reported-by: Dave Chinner <david@xxxxxxxxxxxxx>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
I'm finding the commit log hard to parse/understand.
Let's reference
71a6af8 Revert "xfs_repair: treat zero da btree pointers as corruption"
for starters, but can we do something like this....?
===
As explained in
71a6af8 Revert "xfs_repair: treat zero da btree pointers as corruption"
a single root LEAFN block can exist in a directory until it grows further.
This is why, normally, we skip directories with a root marked
XFS_DIR2_LEAFN_MAGIC, as detected by the left-most leaf block being
found at file block 0.
However, if we traversed any level of a btree to get here (as
indicated by da_cursor.active > 0), then a leaf block claiming block
0 indicates corruption, and we should handle it as such, and rebuild
the directory.
This was found by repair repeatedly rebuilding a directory containing a
single leafn block (xfs/495).
Fixes: 67a79e2cc932 ("xfs_repair: treat zero da btree pointers as corruption")
Reported-by: Dave Chinner <david@xxxxxxxxxxxxx>
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
===
I'm not hung up on rewriting the commit log, but if you like it give me
thumbs up. I needed to think it through that way to grok the change.
Anyway, for the change now that I do grok it,
Reviewed-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> v2: now that the regression test has landed, mention that in the
> changelog
> ---
> repair/dir2.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/repair/dir2.c b/repair/dir2.c
> index ba5763ed..e67ec590 100644
> --- a/repair/dir2.c
> +++ b/repair/dir2.c
> @@ -1243,10 +1243,21 @@ process_node_dir2(
>
> /*
> * Skip directories with a root marked XFS_DIR2_LEAFN_MAGIC
> + *
> + * Be careful here: If any level of the da cursor was filled out then
> + * the directory has a da btree containing an invalid before pointer to
> + * dblock 0, and we should move on to rebuilding the directory. If no
> + * levels in the da cursor got filled out, then we just have a single
> + * leafn block and we're done.
> */
> if (bno == 0) {
> - release_da_cursor(mp, &da_cursor, 0);
> - return 0;
> + if (da_cursor.active > 0) {
> + err_release_da_cursor(mp, &da_cursor, 0);
> + return 1;
> + } else {
> + release_da_cursor(mp, &da_cursor, 0);
> + return 0;
> + }
> } else {
> /*
> * Now pass cursor and bno into leaf-block processing routine.
>
