Re: [RFC PATCH v2 1/2] xfs: add leaf split error tag

[Catherine Hoang <catherine.hoang@oracle.com>]

> On Jan 18, 2022, at 8:47 PM, Darrick J. Wong <djwong@kernel.org> wrote:
> 
> On Mon, Jan 10, 2022 at 09:24:53PM +0000, Catherine Hoang wrote:
>> Add an error tag on xfs_da3_split to test log attribute recovery
>> and replay.
>> 
>> Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
>> Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
>> ---
>> fs/xfs/libxfs/xfs_da_btree.c | 5 +++++
>> fs/xfs/libxfs/xfs_errortag.h | 4 +++-
>> fs/xfs/xfs_error.c           | 3 +++
>> 3 files changed, 11 insertions(+), 1 deletion(-)
>> 
>> diff --git a/fs/xfs/libxfs/xfs_da_btree.c b/fs/xfs/libxfs/xfs_da_btree.c
>> index dd7a2dbce1d1..258a5fef64b2 100644
>> --- a/fs/xfs/libxfs/xfs_da_btree.c
>> +++ b/fs/xfs/libxfs/xfs_da_btree.c
>> @@ -22,6 +22,7 @@
>> #include "xfs_trace.h"
>> #include "xfs_buf_item.h"
>> #include "xfs_log.h"
>> +#include "xfs_errortag.h"
>> 
>> /*
>>  * xfs_da_btree.c
>> @@ -482,6 +483,10 @@ xfs_da3_split(
>> 
>> 	trace_xfs_da_split(state->args);
>> 
>> +	if (XFS_TEST_ERROR(false, state->mp, XFS_ERRTAG_LARP_LEAF_SPLIT)) {
> 
> This error injection knob is in the middle of the dabtree code, so it
> really ought to be namespaced _DA_ and not _LARP_:
> 
> XFS_ERRTAG_DA_LEAF_SPLIT

Ok, this makes sense. Will fix, thanks for the explanation!
> 
> A bit of background: in XFS, directories and extended file attributes
> both start their lives as arrays of variable length records that map a
> name to some sort of binary data.  Directory entries map a human-
> readable bytestring to an inode number, and xattrs map a namespaced
> human-readable bytestring to a blob of binary data.
> 
> To speed up lookups by name, both structures support adding a btree
> index that maps the human-readable name to a hash value, then maps the
> hash value(s) to positions within the array.  Within the xfs codebase,
> that btree is called the "dabtree" to distinguish it from xfs_btree,
> which is a totally different animal.
> 
> Hence, any error injection knobs touching xfs_da* functions really
> should be namespaced _DA_ to match.
> 
> (And for everyone else following along at home, "LARP" refers to Logging
> extended Attributes that are Replayable on Purpose or something like
> that.)
> 
>> +		return -EIO;
>> +	}
> 
> Nit: don't need braces for a single-line if body.
> 
> Other than those two things, this looks good to me.
> 
> --D

Sure, I’ll remove the braces here.
> 
>> +
>> 	/*
>> 	 * Walk back up the tree splitting/inserting/adjusting as necessary.
>> 	 * If we need to insert and there isn't room, split the node, then
>> diff --git a/fs/xfs/libxfs/xfs_errortag.h b/fs/xfs/libxfs/xfs_errortag.h
>> index c15d2340220c..970f3a3f3750 100644
>> --- a/fs/xfs/libxfs/xfs_errortag.h
>> +++ b/fs/xfs/libxfs/xfs_errortag.h
>> @@ -60,7 +60,8 @@
>> #define XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT		37
>> #define XFS_ERRTAG_AG_RESV_FAIL				38
>> #define XFS_ERRTAG_LARP					39
>> -#define XFS_ERRTAG_MAX					40
>> +#define XFS_ERRTAG_LARP_LEAF_SPLIT			40
>> +#define XFS_ERRTAG_MAX					41
>> 
>> /*
>>  * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
>> @@ -105,5 +106,6 @@
>> #define XFS_RANDOM_BMAP_ALLOC_MINLEN_EXTENT		1
>> #define XFS_RANDOM_AG_RESV_FAIL				1
>> #define XFS_RANDOM_LARP					1
>> +#define XFS_RANDOM_LARP_LEAF_SPLIT			1
>> 
>> #endif /* __XFS_ERRORTAG_H_ */
>> diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c
>> index d4b2256ba00b..9cb6743a5ae3 100644
>> --- a/fs/xfs/xfs_error.c
>> +++ b/fs/xfs/xfs_error.c
>> @@ -58,6 +58,7 @@ static unsigned int xfs_errortag_random_default[] = {
>> 	XFS_RANDOM_BMAP_ALLOC_MINLEN_EXTENT,
>> 	XFS_RANDOM_AG_RESV_FAIL,
>> 	XFS_RANDOM_LARP,
>> +	XFS_RANDOM_LARP_LEAF_SPLIT,
>> };
>> 
>> struct xfs_errortag_attr {
>> @@ -172,6 +173,7 @@ XFS_ERRORTAG_ATTR_RW(reduce_max_iextents,	XFS_ERRTAG_REDUCE_MAX_IEXTENTS);
>> XFS_ERRORTAG_ATTR_RW(bmap_alloc_minlen_extent,	XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT);
>> XFS_ERRORTAG_ATTR_RW(ag_resv_fail, XFS_ERRTAG_AG_RESV_FAIL);
>> XFS_ERRORTAG_ATTR_RW(larp,		XFS_ERRTAG_LARP);
>> +XFS_ERRORTAG_ATTR_RW(larp_leaf_split,	XFS_ERRTAG_LARP_LEAF_SPLIT);
>> 
>> static struct attribute *xfs_errortag_attrs[] = {
>> 	XFS_ERRORTAG_ATTR_LIST(noerror),
>> @@ -214,6 +216,7 @@ static struct attribute *xfs_errortag_attrs[] = {
>> 	XFS_ERRORTAG_ATTR_LIST(bmap_alloc_minlen_extent),
>> 	XFS_ERRORTAG_ATTR_LIST(ag_resv_fail),
>> 	XFS_ERRORTAG_ATTR_LIST(larp),
>> +	XFS_ERRORTAG_ATTR_LIST(larp_leaf_split),
>> 	NULL,
>> };
>> 
>> -- 
>> 2.25.1
>>