On Tue, Nov 03, 2020 at 08:36:42PM +0530, Chandan Babu R wrote:
> This commit adds XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT error tag which
> helps userspace test programs to get xfs_bmap_btalloc() to always
> allocate minlen sized extents.
>
> This is required for test programs which need a guarantee that minlen
> extents allocated for a file do not get merged with their existing
> neighbours in the inode's BMBT. "Inode fork extent overflow check" for
> Directories, Xattrs and extension of realtime inodes need this since the
> file offset at which the extents are being allocated cannot be
> explicitly controlled from userspace.
>
> One way to use this error tag is to,
> 1. Consume all of the free space by sequentially writing to a file.
> 2. Punch alternate blocks of the file. This causes CNTBT to contain
> sufficient number of one block sized extent records.
> 3. Inject XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT error tag.
> After step 3, xfs_bmap_btalloc() will issue space allocation
> requests for minlen sized extents only.
>
> ENOSPC error code is returned to userspace when there aren't any "one
> block sized" extents left in any of the AGs.
>
> Signed-off-by: Chandan Babu R <chandanrlinux@xxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_alloc.c | 50 ++++++++++++++
> fs/xfs/libxfs/xfs_alloc.h | 3 +
> fs/xfs/libxfs/xfs_bmap.c | 124 ++++++++++++++++++++++++++++-------
> fs/xfs/libxfs/xfs_errortag.h | 4 +-
> fs/xfs/xfs_error.c | 3 +
> 5 files changed, 159 insertions(+), 25 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 852b536551b5..a7c4eb1d71d5 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -2473,6 +2473,47 @@ xfs_defer_agfl_block(
> xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_AGFL_FREE, &new->xefi_list);
> }
>
> +#ifdef DEBUG
> +/*
> + * Check if an AGF has a free extent record whose length is equal to
> + * args->minlen.
> + */
> +STATIC int
> +xfs_exact_minlen_extent_available(
> + struct xfs_alloc_arg *args,
> + struct xfs_buf *agbp,
> + int *stat)
> +{
> + struct xfs_btree_cur *cnt_cur;
> + xfs_agblock_t fbno;
> + xfs_extlen_t flen;
> + int error = 0;
> +
> + cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, agbp,
> + args->agno, XFS_BTNUM_CNT);
> + error = xfs_alloc_lookup_ge(cnt_cur, 0, args->minlen, stat);
> + if (error)
> + goto out;
> +
> + if (*stat == 0) {
> + error = -EFSCORRUPTED;
> + goto out;
> + }
> +
> + error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen, stat);
> + if (error)
> + goto out;
> +
> + if (*stat == 1 && flen != args->minlen)
> + *stat = 0;
> +
> +out:
> + xfs_btree_del_cursor(cnt_cur, error);
> +
> + return error;
> +}
> +#endif
> +
> /*
> * Decide whether to use this allocation group for this allocation.
> * If so, fix up the btree freelist's size.
> @@ -2544,6 +2585,15 @@ xfs_alloc_fix_freelist(
> if (!xfs_alloc_space_available(args, need, flags))
> goto out_agbp_relse;
>
> +#ifdef DEBUG
> + if (args->alloc_minlen_only) {
> + int stat;
> +
> + error = xfs_exact_minlen_extent_available(args, agbp, &stat);
> + if (error || !stat)
> + goto out_agbp_relse;
> + }
> +#endif
> /*
> * Make the freelist shorter if it's too long.
> *
> diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
> index 6c22b12176b8..a4427c5775c2 100644
> --- a/fs/xfs/libxfs/xfs_alloc.h
> +++ b/fs/xfs/libxfs/xfs_alloc.h
> @@ -75,6 +75,9 @@ typedef struct xfs_alloc_arg {
> char wasfromfl; /* set if allocation is from freelist */
> struct xfs_owner_info oinfo; /* owner of blocks being allocated */
> enum xfs_ag_resv_type resv; /* block reservation to use */
> +#ifdef DEBUG
> + bool alloc_minlen_only; /* allocate exact minlen extent */
> +#endif
> } xfs_alloc_arg_t;
>
> /*
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index f6cd33684571..4717c5f1808e 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -3552,35 +3552,102 @@ xfs_bmap_process_allocated_extent(
> xfs_bmap_btalloc_accounting(ap, args);
> }
>
> +#ifdef DEBUG
> +static int
> +xfs_bmap_exact_minlen_extent_alloc(
> + struct xfs_bmalloca *ap)
> +{
> + struct xfs_mount *mp = ap->ip->i_mount;
> + struct xfs_alloc_arg args = { .tp = ap->tp, .mp = mp };
> + xfs_fileoff_t orig_offset;
> + xfs_extlen_t orig_length;
> + int error;
> +
> + ASSERT(ap->length);
> +
> + if (ap->minlen != 1) {
> + ap->blkno = NULLFSBLOCK;
> + ap->length = 0;
> + return 0;
> + }
> +
> + orig_offset = ap->offset;
> + orig_length = ap->length;
> +
> + args.alloc_minlen_only = 1;
> +
> + xfs_bmap_compute_alignments(ap, &args);
> +
> + if (ap->tp->t_firstblock == NULLFSBLOCK) {
> + /*
> + * Unlike the longest extent available in an AG, we don't track
> + * the length of an AG's shortest extent.
> + * XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT is a debug only knob and
> + * hence we can afford to start traversing from the 0th AG since
> + * we need not be concerned about a drop in performance in
> + * "debug only" code paths.
> + */
> + ap->blkno = XFS_AGB_TO_FSB(mp, 0, 0);
> + } else {
> + ap->blkno = ap->tp->t_firstblock;
> + }
> +
> + args.fsbno = ap->blkno;
> + args.oinfo = XFS_RMAP_OINFO_SKIP_UPDATE;
> + args.type = XFS_ALLOCTYPE_FIRST_AG;
> + args.total = args.minlen = args.maxlen = ap->minlen;
> +
> + args.alignment = 1;
> + args.minalignslop = 0;
> +
> + args.minleft = ap->minleft;
> + args.wasdel = ap->wasdel;
> + args.resv = XFS_AG_RESV_NONE;
> + args.datatype = ap->datatype;
> +
> + error = xfs_alloc_vextent(&args);
> + if (error)
> + return error;
> +
> + if (args.fsbno != NULLFSBLOCK) {
> + xfs_bmap_process_allocated_extent(ap, &args, orig_offset,
> + orig_length);
> + } else {
> + ap->blkno = NULLFSBLOCK;
> + ap->length = 0;
> + }
> +
> + return 0;
> +}
> +#else
> +
> +#define xfs_bmap_exact_minlen_extent_alloc(bma) (-EFSCORRUPTED)
> +
> +#endif
> +
> STATIC int
> xfs_bmap_btalloc(
> struct xfs_bmalloca *ap) /* bmap alloc argument struct */
> {
> - xfs_mount_t *mp; /* mount point structure */
> - xfs_alloctype_t atype = 0; /* type for allocation routines */
> - xfs_agnumber_t fb_agno; /* ag number of ap->firstblock */
> - xfs_agnumber_t ag;
> - xfs_alloc_arg_t args;
> - xfs_fileoff_t orig_offset;
> - xfs_extlen_t orig_length;
> - xfs_extlen_t blen;
> - xfs_extlen_t nextminlen = 0;
> - int nullfb; /* true if ap->firstblock isn't set */
> - int isaligned;
> - int tryagain;
> - int error;
> - int stripe_align;
> + struct xfs_mount *mp = ap->ip->i_mount; /* mount point structure */
> + struct xfs_alloc_arg args = { .tp = ap->tp, .mp = mp };
> + xfs_alloctype_t atype = 0; /* type for allocation routines */
I'll remove these comments ("bmap alloc argument struct", "mount point
structure", "type for allocation routines") that don't add much.
> + xfs_agnumber_t fb_agno; /* ag number of ap->firstblock */
> + xfs_agnumber_t ag;
> + xfs_fileoff_t orig_offset;
> + xfs_extlen_t orig_length;
> + xfs_extlen_t blen;
> + xfs_extlen_t nextminlen = 0;
> + int nullfb; /* true if ap->firstblock isn't set */
> + int isaligned;
> + int tryagain;
> + int error;
> + int stripe_align;
>
> ASSERT(ap->length);
> orig_offset = ap->offset;
> orig_length = ap->length;
>
> - mp = ap->ip->i_mount;
> -
> - memset(&args, 0, sizeof(args));
> - args.tp = ap->tp;
> - args.mp = mp;
> -
> stripe_align = xfs_bmap_compute_alignments(ap, &args);
>
> nullfb = ap->tp->t_firstblock == NULLFSBLOCK;
> @@ -4113,7 +4180,11 @@ xfs_bmap_alloc_userdata(
> return xfs_bmap_rtalloc(bma);
> }
>
> - return xfs_bmap_btalloc(bma);
> + if (unlikely(XFS_TEST_ERROR(false, mp,
> + XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT)))
> + return xfs_bmap_exact_minlen_extent_alloc(bma);
> + else
> + return xfs_bmap_btalloc(bma);
Minor nit: no need for the "else return" here, you can just do:
if (unlikely(...))
return xfs_bmap_exact_minlen_extent_alloc(bma);
return xfs_bmap_btalloc(bma);
I'll just fix those on their way into my testing tree, but please make
the changes to your dev branch if you end up sending a v11.
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> }
>
> static int
> @@ -4149,10 +4220,15 @@ xfs_bmapi_allocate(
> else
> bma->minlen = 1;
>
> - if (bma->flags & XFS_BMAPI_METADATA)
> - error = xfs_bmap_btalloc(bma);
> - else
> + if (bma->flags & XFS_BMAPI_METADATA) {
> + if (unlikely(XFS_TEST_ERROR(false, mp,
> + XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT)))
> + error = xfs_bmap_exact_minlen_extent_alloc(bma);
> + else
> + error = xfs_bmap_btalloc(bma);
> + } else {
> error = xfs_bmap_alloc_userdata(bma);
> + }
> if (error || bma->blkno == NULLFSBLOCK)
> return error;
>
> diff --git a/fs/xfs/libxfs/xfs_errortag.h b/fs/xfs/libxfs/xfs_errortag.h
> index 1c56fcceeea6..6ca9084b6934 100644
> --- a/fs/xfs/libxfs/xfs_errortag.h
> +++ b/fs/xfs/libxfs/xfs_errortag.h
> @@ -57,7 +57,8 @@
> #define XFS_ERRTAG_IUNLINK_FALLBACK 34
> #define XFS_ERRTAG_BUF_IOERROR 35
> #define XFS_ERRTAG_REDUCE_MAX_IEXTENTS 36
> -#define XFS_ERRTAG_MAX 37
> +#define XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT 37
> +#define XFS_ERRTAG_MAX 38
>
> /*
> * Random factors for above tags, 1 means always, 2 means 1/2 time, etc.
> @@ -99,5 +100,6 @@
> #define XFS_RANDOM_IUNLINK_FALLBACK (XFS_RANDOM_DEFAULT/10)
> #define XFS_RANDOM_BUF_IOERROR XFS_RANDOM_DEFAULT
> #define XFS_RANDOM_REDUCE_MAX_IEXTENTS 1
> +#define XFS_RANDOM_BMAP_ALLOC_MINLEN_EXTENT 1
>
> #endif /* __XFS_ERRORTAG_H_ */
> diff --git a/fs/xfs/xfs_error.c b/fs/xfs/xfs_error.c
> index 3780b118cc47..185b4915b7bf 100644
> --- a/fs/xfs/xfs_error.c
> +++ b/fs/xfs/xfs_error.c
> @@ -55,6 +55,7 @@ static unsigned int xfs_errortag_random_default[] = {
> XFS_RANDOM_IUNLINK_FALLBACK,
> XFS_RANDOM_BUF_IOERROR,
> XFS_RANDOM_REDUCE_MAX_IEXTENTS,
> + XFS_RANDOM_BMAP_ALLOC_MINLEN_EXTENT,
> };
>
> struct xfs_errortag_attr {
> @@ -166,6 +167,7 @@ XFS_ERRORTAG_ATTR_RW(bad_summary, XFS_ERRTAG_FORCE_SUMMARY_RECALC);
> 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);
>
> static struct attribute *xfs_errortag_attrs[] = {
> XFS_ERRORTAG_ATTR_LIST(noerror),
> @@ -205,6 +207,7 @@ static struct attribute *xfs_errortag_attrs[] = {
> XFS_ERRORTAG_ATTR_LIST(iunlink_fallback),
> XFS_ERRORTAG_ATTR_LIST(buf_ioerror),
> XFS_ERRORTAG_ATTR_LIST(reduce_max_iextents),
> + XFS_ERRORTAG_ATTR_LIST(bmap_alloc_minlen_extent),
> NULL,
> };
>
> --
> 2.28.0
>
