On Tue, Oct 06, 2020 at 09:55:03AM +0530, Chandan Babu R wrote:
> On Saturday 3 October 2020 11:26:33 AM IST 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 | 46 ++++++++++++++++++++++++++++++++++++
> > fs/xfs/libxfs/xfs_alloc.h | 1 +
> > fs/xfs/libxfs/xfs_bmap.c | 26 ++++++++++++++------
> > fs/xfs/libxfs/xfs_errortag.h | 4 +++-
> > fs/xfs/xfs_error.c | 3 +++
> > 5 files changed, 72 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> > index 852b536551b5..d8d8ab1478db 100644
> > --- a/fs/xfs/libxfs/xfs_alloc.c
> > +++ b/fs/xfs/libxfs/xfs_alloc.c
> > @@ -2473,6 +2473,45 @@ xfs_defer_agfl_block(
> > xfs_defer_add(tp, XFS_DEFER_OPS_TYPE_AGFL_FREE, &new->xefi_list);
> > }
> >
> > +STATIC int
> > +minlen_freespace_available(
> > + struct xfs_alloc_arg *args,
> > + struct xfs_buf *agbp,
> > + int *stat)
> > +{
> > + xfs_btree_cur_t *cnt_cur;
> > + xfs_agblock_t fbno;
> > + xfs_extlen_t flen;
> > + int btree_error = XFS_BTREE_NOERROR;
> > + 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) {
> > + btree_error = XFS_BTREE_ERROR;
> > + goto out;
> > + }
> > +
> > + ASSERT(*stat == 1);
> > +
> > + error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen, stat);
> > + if (error) {
> > + btree_error = XFS_BTREE_ERROR;
> > + goto out;
> > + }
> > +
> > + if (flen == args->minlen)
> > + *stat = 1;
> > + else
> > + *stat = 0;
> > +
> > +out:
> > + xfs_btree_del_cursor(cnt_cur, btree_error);
> > +
> > + return error;
> > +}
> > +
> > /*
> > * Decide whether to use this allocation group for this allocation.
> > * If so, fix up the btree freelist's size.
> > @@ -2490,6 +2529,7 @@ xfs_alloc_fix_freelist(
> > struct xfs_alloc_arg targs; /* local allocation arguments */
> > xfs_agblock_t bno; /* freelist block */
> > xfs_extlen_t need; /* total blocks needed in freelist */
> > + int i;
> > int error = 0;
> >
> > /* deferred ops (AGFL block frees) require permanent transactions */
> > @@ -2544,6 +2584,12 @@ xfs_alloc_fix_freelist(
> > if (!xfs_alloc_space_available(args, need, flags))
> > goto out_agbp_relse;
> >
> > + if (args->alloc_minlen_only) {
> > + error = minlen_freespace_available(args, agbp, &i);
> > + if (error || !i)
> > + goto out_agbp_relse;
> > + }
> > +
> > /*
> > * 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..1d04089b7fb4 100644
> > --- a/fs/xfs/libxfs/xfs_alloc.h
> > +++ b/fs/xfs/libxfs/xfs_alloc.h
> > @@ -75,6 +75,7 @@ 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 */
> > + bool alloc_minlen_only;
> > } xfs_alloc_arg_t;
> >
> > /*
> > diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> > index 5156cbd476f2..fab4097e7492 100644
> > --- a/fs/xfs/libxfs/xfs_bmap.c
> > +++ b/fs/xfs/libxfs/xfs_bmap.c
> > @@ -3510,12 +3510,19 @@ xfs_bmap_btalloc(
> > ASSERT(ap->length);
> > }
> >
> > + memset(&args, 0, sizeof(args));
> > +
> > + args.alloc_minlen_only = XFS_TEST_ERROR(false, mp,
> > + XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT);
> >
> > nullfb = ap->tp->t_firstblock == NULLFSBLOCK;
> > fb_agno = nullfb ? NULLAGNUMBER : XFS_FSB_TO_AGNO(mp,
> > ap->tp->t_firstblock);
> > if (nullfb) {
> > - if ((ap->datatype & XFS_ALLOC_USERDATA) &&
> > + if (args.alloc_minlen_only) {
> > + ag = 0;
> > + ap->blkno = XFS_AGB_TO_FSB(mp, ag, 0);
> > + } else if ((ap->datatype & XFS_ALLOC_USERDATA) &&
> > xfs_inode_is_filestream(ap->ip)) {
> > ag = xfs_filestream_lookup_ag(ap->ip);
> > ag = (ag != NULLAGNUMBER) ? ag : 0;
> > @@ -3523,10 +3530,12 @@ xfs_bmap_btalloc(
> > } else {
> > ap->blkno = XFS_INO_TO_FSB(mp, ap->ip->i_ino);
> > }
> > - } else
> > + } else {
> > ap->blkno = ap->tp->t_firstblock;
> > + }
> >
> > - xfs_bmap_adjacent(ap);
> > + if (!args.alloc_minlen_only)
> > + xfs_bmap_adjacent(ap);
> >
> > /*
> > * If allowed, use ap->blkno; otherwise must use firstblock since
> > @@ -3540,7 +3549,6 @@ xfs_bmap_btalloc(
> > * Normal allocation, done through xfs_alloc_vextent.
> > */
> > tryagain = isaligned = 0;
> > - memset(&args, 0, sizeof(args));
> > args.tp = ap->tp;
> > args.mp = mp;
> > args.fsbno = ap->blkno;
> > @@ -3549,7 +3557,10 @@ xfs_bmap_btalloc(
> > /* Trim the allocation back to the maximum an AG can fit. */
> > args.maxlen = min(ap->length, mp->m_ag_max_usable);
> > blen = 0;
> > - if (nullfb) {
> > + if (args.alloc_minlen_only) {
> > + args.type = XFS_ALLOCTYPE_START_AG;
>
> The above should have been,
>
> args.type = XFS_ALLOCTYPE_FIRST_AG;
>
> In my experiments, I had introduced a new args.type value and had later
> realized that XFS_ALLOCTYPE_FIRST_AG would suffice for my requirements. I had
> tested the changed version (which was in my git stash) and forgot to apply
> that to this commit after testing was completed. Hence I ended up sending a
> slightly stale patch. I am sorry about this. I will resend the series.
Ok, but wait till I've gotten all the way through the replies (nearly
done now).
--D
> --
> chandan
>
>
>
