On 12/4/18 9:48 PM, Eric Sandeen wrote:
> 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>
Uh, the summary is wrong too, o? We /already/ "don't error out"
on dirs with a single leafn block. Maybe:
xfs_repair: rebuild directory when non-root leafn blocks claim block 0
?
