On Mon, Sep 16, 2019 at 08:16:28AM -0400, Brian Foster wrote:
> If the size lookup lands in the last block of the by-size btree, the
> near mode algorithm scans the entire block for the extent with best
> available locality. In preparation for similar best available
> extent tracking across both btrees, extend the allocation cursor
> with best extent data and lift the associated state from the cntbt
> last block scan code. No functional changes.
>
> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
> ---
> fs/xfs/libxfs/xfs_alloc.c | 63 ++++++++++++++++++++-------------------
> 1 file changed, 33 insertions(+), 30 deletions(-)
>
> diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
> index 5c34d4c41761..ee46989ab723 100644
> --- a/fs/xfs/libxfs/xfs_alloc.c
> +++ b/fs/xfs/libxfs/xfs_alloc.c
> @@ -716,6 +716,11 @@ struct xfs_alloc_cur {
> struct xfs_btree_cur *cnt; /* btree cursors */
> struct xfs_btree_cur *bnolt;
> struct xfs_btree_cur *bnogt;
> + xfs_agblock_t rec_bno;/* extent startblock */
> + xfs_extlen_t rec_len;/* extent length */
> + xfs_agblock_t bno; /* alloc bno */
> + xfs_extlen_t len; /* alloc len */
> + xfs_extlen_t diff; /* diff from search bno */
> unsigned busy_gen;/* busy state */
> bool busy;
> };
> @@ -735,6 +740,11 @@ xfs_alloc_cur_setup(
>
> ASSERT(args->alignment == 1 || args->type != XFS_ALLOCTYPE_THIS_BNO);
>
> + acur->rec_bno = 0;
> + acur->rec_len = 0;
> + acur->bno = 0;
> + acur->len = 0;
> + acur->diff = -1;
xfs_extlen_t is a uint32_t; is this going to cause comparison problems?
Also ... assuming that acur->diff is the successor to the bdiff variable
below, shouldn't it be initialized to zero like bdiff was?
--D
> acur->busy = false;
> acur->busy_gen = 0;
>
> @@ -1247,10 +1257,7 @@ xfs_alloc_ag_vextent_near(
> * but we never loop back to the top.
> */
> while (xfs_btree_islastblock(acur.cnt, 0)) {
> - xfs_extlen_t bdiff;
> - int besti=0;
> - xfs_extlen_t blen=0;
> - xfs_agblock_t bnew=0;
> + xfs_extlen_t diff;
>
> #ifdef DEBUG
> if (dofirst)
> @@ -1281,8 +1288,8 @@ xfs_alloc_ag_vextent_near(
> break;
> }
> i = acur.cnt->bc_ptrs[0];
> - for (j = 1, blen = 0, bdiff = 0;
> - !error && j && (blen < args->maxlen || bdiff > 0);
> + for (j = 1;
> + !error && j && (acur.len < args->maxlen || acur.diff > 0);
> error = xfs_btree_increment(acur.cnt, 0, &j)) {
> /*
> * For each entry, decide if it's better than
> @@ -1301,44 +1308,40 @@ xfs_alloc_ag_vextent_near(
> args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
> xfs_alloc_fix_len(args);
> ASSERT(args->len >= args->minlen);
> - if (args->len < blen)
> + if (args->len < acur.len)
> continue;
> - ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
> + diff = xfs_alloc_compute_diff(args->agbno, args->len,
> args->alignment, args->datatype, ltbnoa,
> ltlena, <new);
> if (ltnew != NULLAGBLOCK &&
> - (args->len > blen || ltdiff < bdiff)) {
> - bdiff = ltdiff;
> - bnew = ltnew;
> - blen = args->len;
> - besti = acur.cnt->bc_ptrs[0];
> + (args->len > acur.len || diff < acur.diff)) {
> + acur.rec_bno = ltbno;
> + acur.rec_len = ltlen;
> + acur.diff = diff;
> + acur.bno = ltnew;
> + acur.len = args->len;
> }
> }
> /*
> * It didn't work. We COULD be in a case where
> * there's a good record somewhere, so try again.
> */
> - if (blen == 0)
> + if (acur.len == 0)
> break;
> - /*
> - * Point at the best entry, and retrieve it again.
> - */
> - acur.cnt->bc_ptrs[0] = besti;
> - error = xfs_alloc_get_rec(acur.cnt, <bno, <len, &i);
> - if (error)
> - goto out;
> - XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, out);
> - ASSERT(ltbno + ltlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
> - args->len = blen;
>
> /*
> - * We are allocating starting at bnew for blen blocks.
> + * Allocate at the bno/len tracked in the cursor.
> */
> - args->agbno = bnew;
> - ASSERT(bnew >= ltbno);
> - ASSERT(bnew + blen <= ltbno + ltlen);
> - error = xfs_alloc_fixup_trees(acur.cnt, acur.bnolt, ltbno,
> - ltlen, bnew, blen, XFSA_FIXUP_CNT_OK);
> + args->agbno = acur.bno;
> + args->len = acur.len;
> + ASSERT(acur.bno >= acur.rec_bno);
> + ASSERT(acur.bno + acur.len <= acur.rec_bno + acur.rec_len);
> + ASSERT(acur.rec_bno + acur.rec_len <=
> + be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
> +
> + error = xfs_alloc_fixup_trees(acur.cnt, acur.bnolt,
> + acur.rec_bno, acur.rec_len, acur.bno, acur.len,
> + 0);
> if (error)
> goto out;
> trace_xfs_alloc_near_first(args);
> --
> 2.20.1
>
