Re: [PATCH V7 14/14] xfs: Introduce error injection to allocate only minlen size extents for files

Chandan Babu R
2020-10-26T03:23:27Z

On Sunday 25 October 2020 6:52:53 AM IST Allison Henderson wrote:
>
> On 10/18/20 11:40 PM, 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@gmail.com>
> > ---
> > fs/xfs/libxfs/xfs_alloc.c | 50 ++++++++++++++++++
> > fs/xfs/libxfs/xfs_alloc.h | 3 ++
> > fs/xfs/libxfs/xfs_bmap.c | 100 +++++++++++++++++++++++++++++++----
> > fs/xfs/libxfs/xfs_errortag.h | 4 +-
> > fs/xfs/xfs_error.c | 3 ++
> > 5 files changed, 150 insertions(+), 10 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> > index 852b536551b5..8e132f8b9cc4 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 i;
> Just a nit: I think "i" seems like a bit of an odd name here. I think I
> might have called it stat to match its parameter name. Other than that,
> I think the rest looks ok.

Ok, I will rename "i" with "stat" as you have suggested.

Thank you for reviewing the patchset.

>
> Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
> Allison
> > +
> > + error = xfs_exact_minlen_extent_available(args, agbp, &i);
> > + if (error || !i)
> > + 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 88db23afc51c..74e148cc41b2 100644
> > --- a/fs/xfs/libxfs/xfs_bmap.c
> > +++ b/fs/xfs/libxfs/xfs_bmap.c
> > @@ -3474,11 +3474,13 @@ xfs_bmap_compute_alignments(
> > int error;
> >
> > /* stripe alignment for allocation is determined by mount parameters */
> > - *stripe_align = 0;
> > - if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
> > - *stripe_align = mp->m_swidth;
> > - else if (mp->m_dalign)
> > - *stripe_align = mp->m_dalign;
> > + if (stripe_align) {
> > + *stripe_align = 0;
> > + if (mp->m_swidth && (mp->m_flags & XFS_MOUNT_SWALLOC))
> > + *stripe_align = mp->m_swidth;
> > + else if (mp->m_dalign)
> > + *stripe_align = mp->m_dalign;
> > + }
> >
> > if (ap->flags & XFS_BMAPI_COWFORK)
> > align = xfs_get_cowextsz_hint(ap->ip);
> > @@ -3551,6 +3553,71 @@ 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_alloc_arg args;
> > + struct xfs_mount *mp = ap->ip->i_mount;
> > + xfs_fileoff_t orig_offset;
> > + xfs_extlen_t orig_length;
> > + int error;
> > +
> > + ASSERT(ap->length);
> > + orig_offset = ap->offset;
> > + orig_length = ap->length;
> > +
> > + memset(&args, 0, sizeof(args));
> > + args.alloc_minlen_only = 1;
> > + args.tp = ap->tp;
> > + args.mp = mp;
> > +
> > + xfs_bmap_compute_alignments(ap, &args, NULL);
> > +
> > + 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;
> > +}
> > +#endif
> > +
> > STATIC int
> > xfs_bmap_btalloc(
> > struct xfs_bmalloca *ap) /* bmap alloc argument struct */
> > @@ -4112,7 +4179,13 @@ xfs_bmap_alloc_userdata(
> > return xfs_bmap_rtalloc(bma);
> > }
> >
> > - return xfs_bmap_btalloc(bma);
> > +#ifdef DEBUG
> > + if (unlikely(XFS_TEST_ERROR(false, mp,
> > + XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT)))
> > + return xfs_bmap_exact_minlen_extent_alloc(bma);
> > + else
> > +#endif
> > + return xfs_bmap_btalloc(bma);
> > }
> >
> > static int
> > @@ -4148,10 +4221,19 @@ 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) {
> > +#ifdef DEBUG
> > + if (unlikely(XFS_TEST_ERROR(false, mp,
> > + XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT)))
> > + error = xfs_bmap_exact_minlen_extent_alloc(bma);
> > + else
> > +#endif
> > + 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,
> > };
> >
> >
>

--
chandan