Re: [PATCH v7 5/5] xfs: add error injection for per-AG resv failure

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

On Tue, Mar 02, 2021 at 10:48:16AM +0800, Gao Xiang wrote:
> per-AG resv failure after fixing up freespace is hard to test in an
> effective way, so directly add an error injection path to observe
> such error handling path works as expected.
> 
> Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_ag_resv.c  | 6 +++++-
>  fs/xfs/libxfs/xfs_errortag.h | 4 +++-
>  fs/xfs/xfs_error.c           | 2 ++
>  3 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c
> index fdfe6dc0d307..6c5f8d10589c 100644
> --- a/fs/xfs/libxfs/xfs_ag_resv.c
> +++ b/fs/xfs/libxfs/xfs_ag_resv.c
> @@ -211,7 +211,11 @@ __xfs_ag_resv_init(
>  		ASSERT(0);
>  		return -EINVAL;
>  	}
> -	error = xfs_mod_fdblocks(mp, -(int64_t)hidden_space, true);
> +
> +	if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_AG_RESV_FAIL))
> +		error = -ENOSPC;
> +	else
> +		error = xfs_mod_fdblocks(mp, -(int64_t)hidden_space, true);
>  	if (error) {
>  		trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
>  				error, _RET_IP_);
> diff --git a/fs/xfs/libxfs/xfs_errortag.h b/fs/xfs/libxfs/xfs_errortag.h
> index 6ca9084b6934..b433ef735217 100644
> --- a/fs/xfs/libxfs/xfs_errortag.h
> +++ b/fs/xfs/libxfs/xfs_errortag.h
> @@ -40,6 +40,7 @@
>  #define XFS_ERRTAG_REFCOUNT_FINISH_ONE			25
>  #define XFS_ERRTAG_BMAP_FINISH_ONE			26
>  #define XFS_ERRTAG_AG_RESV_CRITICAL			27
> +

Extra space?

>  /*
>   * DEBUG mode instrumentation to test and/or trigger delayed allocation
>   * block killing in the event of failed writes. When enabled, all
> @@ -58,7 +59,8 @@
>  #define XFS_ERRTAG_BUF_IOERROR				35
>  #define XFS_ERRTAG_REDUCE_MAX_IEXTENTS			36
>  #define XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT		37
> -#define XFS_ERRTAG_MAX					38
> +#define XFS_ERRTAG_AG_RESV_FAIL				38
> +#define XFS_ERRTAG_MAX					39
>  
>  /*
>   * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.

This needs to define XFS_RANDOM_AG_RESV_FAIL and put it in
xfs_errortag_random_default in xfs_error.c to avoid running off the end
of the array.

Also... that _default array /really/ needs to have a BUILD_BUG_ON
somewhere to scream loudly if it isn't XFS_ERRTAG_MAX elements long.

--D

> diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c
> index 185b4915b7bf..5192a7063d95 100644
> --- a/fs/xfs/xfs_error.c
> +++ b/fs/xfs/xfs_error.c
> @@ -168,6 +168,7 @@ XFS_ERRORTAG_ATTR_RW(iunlink_fallback,	XFS_ERRTAG_IUNLINK_FALLBACK);
>  XFS_ERRORTAG_ATTR_RW(buf_ioerror,	XFS_ERRTAG_BUF_IOERROR);
>  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);
>  
>  static struct attribute *xfs_errortag_attrs[] = {
>  	XFS_ERRORTAG_ATTR_LIST(noerror),
> @@ -208,6 +209,7 @@ static struct attribute *xfs_errortag_attrs[] = {
>  	XFS_ERRORTAG_ATTR_LIST(buf_ioerror),
>  	XFS_ERRORTAG_ATTR_LIST(reduce_max_iextents),
>  	XFS_ERRORTAG_ATTR_LIST(bmap_alloc_minlen_extent),
> +	XFS_ERRORTAG_ATTR_LIST(ag_resv_fail),
>  	NULL,
>  };
>  
> -- 
> 2.27.0
>