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

["Darrick J. Wong" <djwong@kernel.org>]

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

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

> +
>  	/*
>  	 * 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
>