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Wong" Cc: linux-xfs@vger.kernel.org, david@fromorbit.com, hch@infradead.org, allison.henderson@oracle.com Subject: Re: [PATCH V10 14/14] xfs: Introduce error injection to allocate only minlen size extents for files Date: Wed, 04 Nov 2020 08:52:41 +0530 Message-ID: <1714718.glcqsSTdsc@garuda> In-Reply-To: <20201103195651.GB7115@magnolia> References: <20201103150642.2032284-1-chandanrlinux@gmail.com> <20201103150642.2032284-15-chandanrlinux@gmail.com> <20201103195651.GB7115@magnolia> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wednesday 4 November 2020 1:26:51 AM IST Darrick J. Wong wrote: > 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 > > --- > > 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. Sure. I will do that. > > Reviewed-by: Darrick J. Wong > > --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, > > }; > > > -- chandan