[PATCH v3 2/4] xfs: use locality optimized cntbt lookups for near mode allocations

Brian Foster
2019-08-15T12:55:40Z

The extent allocation code in XFS has several allocation modes with
unique implementations. These modes are not all that different from
a high level perspective. The most involved mode is near allocation
mode which attempts to allocate an optimally sized extent with ideal
locality with respect to a provided agbno hint.

In the common case, a near mode allocation consists of a conditional
scan of the last cntbt block followed by a concurrent left and right
spanning search of the bnobt starting from the ideal point of
locality in the bnobt. This works reasonably well as filesystems age
via most common allocation patterns. If free space fragments as the
filesystem ages, however, the near algorithm has very poor breakdown
characteristics. If the extent size lookup happens to land outside
(i.e., before) the last cntbt block, the alloc bypasses the cntbt
entirely. If a suitably sized extent is far enough away from the
starting points of the bnobt search, the left/right scans can take a
significant amount of time to locate the target extent. This leads
to pathological allocation latencies in certain workloads.

While locality is important to near mode allocations, it is not so
important as to incur pathological allocation latency to provide the
asolute best locality for every allocation. The left/right bnobt
scan is inefficient in many large allocation scenarios. As an
alternative, we can use locality optimized lookups of the cntbt to
find the closest extent to the target agbno of a particular size. We
can repeat this lookup to cover a larger span of extents much more
efficiently. Finally, we can combine this cntbt lookup algorithm
with the existing bnobt scan to provide a natural balance between
the two for large and small allocations. For example, the bnobt scan
may be able to satisfy inode chunk or btree block allocations fairly
quickly where the cntbt search may have to search through a large
set of extent sizes. On the other hand, the cntbt search can more
deterministically scan the set of free extents available for much
larger delayed allocation requests where the bnobt scan may have to
search the entire AG.

Rework the near mode allocation algorithm as described above to
provide predictable allocation latency under breakdown conditions
with good enough locality in the common case. In doing so, refactor
the affected code into a more generic interface and mechanisms to
facilitate future reuse by the by-size and exact mode algorithms.
Both allocation modes currently have unique, ground-up
implementations that can be replaced with minimal logic additions to
the generic code in this patch.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
fs/xfs/libxfs/xfs_alloc.c | 1045 +++++++++++++++++++------------------
fs/xfs/xfs_trace.h | 43 +-
2 files changed, 581 insertions(+), 507 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 6340f59ac3f4..7753b61ba532 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -37,7 +37,6 @@ struct workqueue_struct *xfs_alloc_wq;
#define XFSA_FIXUP_CNT_OK 2

STATIC int xfs_alloc_ag_vextent_exact(xfs_alloc_arg_t *);
-STATIC int xfs_alloc_ag_vextent_near(xfs_alloc_arg_t *);
STATIC int xfs_alloc_ag_vextent_size(xfs_alloc_arg_t *);

/*
@@ -710,8 +709,446 @@ xfs_alloc_update_counters(
}

/*
- * Allocation group level functions.
+ * Block allocation algorithm and data structures.
*/
+struct xfs_alloc_cur {
+ struct xfs_btree_cur *cnt; /* btree cursors */
+ struct xfs_btree_cur *bnolt;
+ struct xfs_btree_cur *bnogt;
+ xfs_extlen_t cur_len;/* current search length */
+ 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;
+};
+
+/*
+ * Set up cursors, etc. in the extent allocation cursor. This function can be
+ * called multiple times to reset an initialized structure without having to
+ * reallocate cursors.
+ */
+static int
+xfs_alloc_cur_setup(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur)
+{
+ int error;
+ int i;
+
+ ASSERT(args->alignment == 1 || args->type != XFS_ALLOCTYPE_THIS_BNO);
+
+ acur->cur_len = args->maxlen;
+ acur->rec_bno = 0;
+ acur->rec_len = 0;
+ acur->bno = 0;
+ acur->len = 0;
+ acur->diff = -1;
+ acur->busy = false;
+ acur->busy_gen = 0;
+
+ /*
+ * Allocate the cntbt cursor and set the starting search length to
+ * maxlen or minlen.
+ */
+ if (!acur->cnt)
+ acur->cnt = xfs_allocbt_init_cursor(args->mp, args->tp,
+ args->agbp, args->agno, XFS_BTNUM_CNT);
+ error = xfs_alloc_lookup_ge(acur->cnt, 0, acur->cur_len, &i);
+ if (!error && !i && args->maxlen != args->minlen) {
+ acur->cur_len = args->minlen;
+ error = xfs_alloc_lookup_ge(acur->cnt, 0, acur->cur_len, &i);
+ }
+ if (error)
+ return error;
+ if (!i)
+ return -ENOSPC;
+
+ /*
+ * Allocate the bnobt left and right search cursors.
+ */
+ if (!acur->bnolt)
+ acur->bnolt = xfs_allocbt_init_cursor(args->mp, args->tp,
+ args->agbp, args->agno, XFS_BTNUM_BNO);
+ if (!acur->bnogt)
+ acur->bnogt = xfs_allocbt_init_cursor(args->mp, args->tp,
+ args->agbp, args->agno, XFS_BTNUM_BNO);
+ return 0;
+}
+
+static void
+xfs_alloc_cur_close(
+ struct xfs_alloc_cur *acur,
+ bool error)
+{
+ int cur_error = XFS_BTREE_NOERROR;
+
+ if (error)
+ cur_error = XFS_BTREE_ERROR;
+
+ if (acur->cnt)
+ xfs_btree_del_cursor(acur->cnt, cur_error);
+ if (acur->bnolt)
+ xfs_btree_del_cursor(acur->bnolt, cur_error);
+ if (acur->bnogt)
+ xfs_btree_del_cursor(acur->bnogt, cur_error);
+ acur->cnt = acur->bnolt = acur->bnogt = NULL;
+}
+
+/*
+ * Check an extent for allocation and track the best available candidate in the
+ * allocation structure. The cursor is deactivated if it has entered an out of
+ * range state based on allocation arguments. Optionally return the extent
+ * extent geometry and allocation status if requested by the caller.
+ */
+static int
+xfs_alloc_cur_check(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ struct xfs_btree_cur *cur,
+ int *new)
+{
+ int error, i;
+ xfs_agblock_t bno, bnoa, bnew;
+ xfs_extlen_t len, lena, diff = -1;
+ bool busy;
+ unsigned busy_gen = 0;
+ bool deactivate = false;
+ bool isbnobt = cur->bc_btnum == XFS_BTNUM_BNO;
+
+ *new = 0;
+
+ error = xfs_alloc_get_rec(cur, &bno, &len, &i);
+ if (error)
+ return error;
+ XFS_WANT_CORRUPTED_RETURN(args->mp, i == 1);
+
+ /*
+ * Check minlen and deactivate a cntbt cursor if out of acceptable size
+ * range (i.e., walking backwards looking for a minlen extent).
+ */
+ if (len < args->minlen) {
+ deactivate = !isbnobt;
+ goto out;
+ }
+
+ busy = xfs_alloc_compute_aligned(args, bno, len, &bnoa, &lena,
+ &busy_gen);
+ acur->busy |= busy;
+ if (busy)
+ acur->busy_gen = busy_gen;
+ /* deactivate a bnobt cursor outside of locality range */
+ if (bnoa < args->min_agbno || bnoa > args->max_agbno) {
+ deactivate = isbnobt;
+ goto out;
+ }
+ if (lena < args->minlen)
+ goto out;
+
+ args->len = XFS_EXTLEN_MIN(lena, args->maxlen);
+ xfs_alloc_fix_len(args);
+ ASSERT(args->len >= args->minlen);
+ if (args->len < acur->len)
+ goto out;
+
+ /*
+ * We have an aligned record that satisfies minlen and beats or matches
+ * the candidate extent size. Compare locality for near allocation mode.
+ */
+ ASSERT(args->type == XFS_ALLOCTYPE_NEAR_BNO);
+ diff = xfs_alloc_compute_diff(args->agbno, args->len,
+ args->alignment, args->datatype,
+ bnoa, lena, &bnew);
+ if (bnew == NULLAGBLOCK)
+ goto out;
+
+ /*
+ * We always prioritize allocation size over locality, so select this
+ * extent if it is larger or matches size with equal or better locality.
+ * Don't filter out equivalent extents because the higher level
+ * algorithm can use selection from particular cursors to terminate the
+ * search. For example, a bnobt cursor maxlen hit means this is the
+ * optimal free extent.
+ */
+ if (args->len == acur->len && diff > acur->diff) {
+ deactivate = isbnobt;
+ goto out;
+ }
+
+ ASSERT(args->len > acur->len ||
+ (args->len == acur->len && diff <= acur->diff));
+ acur->rec_bno = bno;
+ acur->rec_len = len;
+ acur->bno = bnew;
+ acur->len = args->len;
+ acur->diff = diff;
+ *new = 1;
+out:
+ if (deactivate)
+ cur->bc_private.a.priv.abt.active = false;
+ trace_xfs_alloc_cur_check(args->mp, cur->bc_btnum, bno, len, diff,
+ *new);
+ return 0;
+}
+
+/*
+ * Complete an allocation of a candidate extent. Remove the extent from both
+ * trees and update the args structure.
+ */
+STATIC int
+xfs_alloc_cur_finish(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur)
+{
+ int error;
+
+ ASSERT(acur->len);
+ ASSERT(acur->cnt && acur->bnolt);
+
+ error = xfs_alloc_fixup_trees(acur->cnt, acur->bnolt, acur->rec_bno,
+ acur->rec_len, acur->bno, acur->len, 0);
+ if (error)
+ return error;
+
+ args->agbno = acur->bno;
+ args->len = acur->len;
+ args->wasfromfl = 0;
+
+ trace_xfs_alloc_cur(args);
+ return 0;
+}
+
+/*
+ * Locality allocation lookup algorithm. This expects a cntbt cursor and uses
+ * bno optimized lookup to search for extents with ideal size and locality.
+ */
+STATIC int
+xfs_alloc_lookup_iter(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ struct xfs_btree_cur *cur)
+{
+ xfs_agblock_t bno;
+ xfs_extlen_t len, cur_len;
+ int error;
+ int i;
+
+ if (!xfs_alloc_cur_active(cur))
+ return 0;
+
+ /* locality optimized lookup */
+ cur_len = acur->cur_len;
+ error = xfs_alloc_lookup_ge(cur, args->agbno, cur_len, &i);
+ if (error)
+ return error;
+ if (i == 0)
+ return 0;
+ error = xfs_alloc_get_rec(cur, &bno, &len, &i);
+ if (error)
+ return error;
+
+ /* check the current record and update search length from it */
+ error = xfs_alloc_cur_check(args, acur, cur, &i);
+ if (error)
+ return error;
+ ASSERT(len >= acur->cur_len);
+ acur->cur_len = len;
+
+ /*
+ * We looked up the first record >= [agbno, len] above. The agbno is a
+ * secondary key and so the current record may lie just before or after
+ * agbno. If it is past agbno, check the previous record too so long as
+ * the length matches as it may be closer. Don't check a smaller record
+ * because that could deactivate our cursor.
+ */
+ if (bno > args->agbno) {
+ error = xfs_btree_decrement(cur, 0, &i);
+ if (!error && i) {
+ error = xfs_alloc_get_rec(cur, &bno, &len, &i);
+ if (!error && i && len == acur->cur_len)
+ error = xfs_alloc_cur_check(args, acur, cur,
+ &i);
+ }
+ if (error)
+ return error;
+ }
+
+ /*
+ * Increment the search key until we find at least one allocation
+ * candidate or if the extent we found was larger. Otherwise, double the
+ * search key to optimize the search. Efficiency is more important here
+ * than absolute best locality.
+ */
+ cur_len <<= 1;
+ if (!acur->len || acur->cur_len >= cur_len)
+ acur->cur_len++;
+ else
+ acur->cur_len = cur_len;
+
+ return error;
+}
+
+/*
+ * Incremental lookup algorithm. Walk a btree in either direction looking for
+ * candidate extents. This works for either bnobt (locality allocation) or cntbt
+ * (by-size allocation) cursors.
+ */
+STATIC int
+xfs_alloc_walk_iter(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ struct xfs_btree_cur *cur,
+ bool increment,
+ bool findone,
+ int iters,
+ int *stat)
+{
+ int error;
+ int i;
+
+ *stat = 0;
+
+ if (!xfs_alloc_cur_active(cur))
+ return 0;
+
+ for (; iters > 0; iters--) {
+ error = xfs_alloc_cur_check(args, acur, cur, &i);
+ if (error)
+ return error;
+ if (i) {
+ *stat = 1;
+ if (findone)
+ break;
+ }
+ if (!xfs_alloc_cur_active(cur))
+ break;
+
+ if (increment)
+ error = xfs_btree_increment(cur, 0, &i);
+ else
+ error = xfs_btree_decrement(cur, 0, &i);
+ if (error)
+ return error;
+ if (i == 0) {
+ cur->bc_private.a.priv.abt.active = false;
+ break;
+ }
+ }
+
+ return error;
+}
+
+/*
+ * High level locality allocation algorithm. Search the bnobt (left and right)
+ * in parallel with locality-optimized cntbt lookups to find an extent with
+ * ideal locality.
+ */
+STATIC int
+xfs_alloc_ag_vextent_lookup(
+ struct xfs_alloc_arg *args,
+ struct xfs_alloc_cur *acur,
+ int *stat)
+{
+ int error;
+ int i;
+ struct xfs_btree_cur *fbcur = NULL;
+ bool fbinc = false;
+
+ ASSERT(acur->cnt);
+ ASSERT(args->type == XFS_ALLOCTYPE_NEAR_BNO);
+ *stat = 0;
+
+ /*
+ * Set up available cursors for a locality allocation search based on
+ * the ->agbno hint. An exact allocation only needs the bnolt so disable
+ * the cntbt cursor explicitly.
+ */
+ error = xfs_alloc_lookup_ge(acur->cnt, args->agbno, acur->cur_len, &i);
+ if (error)
+ return error;
+ error = xfs_alloc_lookup_le(acur->bnolt, args->agbno, 0, &i);
+ if (error)
+ return error;
+ error = xfs_alloc_lookup_ge(acur->bnogt, args->agbno, 0, &i);
+ if (error)
+ return error;
+
+ /* search as long as we have at least one active cursor */
+ while (xfs_alloc_cur_active(acur->cnt) ||
+ xfs_alloc_cur_active(acur->bnolt) ||
+ xfs_alloc_cur_active(acur->bnogt)) {
+ trace_xfs_alloc_cur_lookup(args);
+
+ /*
+ * Search the bnobt left and right. If either of these find a
+ * maxlen extent, we know we've found ideal locality. Do a
+ * capped search in the opposite direction and we're done.
+ */
+ error = xfs_alloc_walk_iter(args, acur, acur->bnolt, false,
+ true, 1, &i);
+ if (error)
+ return error;
+ if (i && acur->len == args->maxlen) {
+ trace_xfs_alloc_cur_left(args);
+ fbcur = acur->bnogt;
+ fbinc = true;
+ break;
+ }
+
+ error = xfs_alloc_walk_iter(args, acur, acur->bnogt, true,
+ true, 1, &i);
+ if (error)
+ return error;
+ if (i && acur->len == args->maxlen) {
+ trace_xfs_alloc_cur_right(args);
+ fbcur = acur->bnolt;
+ break;
+ }
+
+ /*
+ * Search the cntbt for a maximum sized extent with ideal
+ * locality. The lookup search terminates on reaching the end of
+ * the cntbt. Break out of the loop if this occurs to throttle
+ * the bnobt scans.
+ */
+ error = xfs_alloc_lookup_iter(args, acur, acur->cnt);
+ if (error)
+ return error;
+ if (!xfs_alloc_cur_active(acur->cnt)) {
+ trace_xfs_alloc_cur_lookup_done(args);
+ if (!acur->len) {
+ /*
+ * Reset the cursor for a minlen search in the
+ * caller.
+ */
+ error = xfs_btree_decrement(acur->cnt, 0, &i);
+ if (error)
+ return error;
+ if (i)
+ acur->cnt->bc_private.a.priv.abt.active = true;
+ }
+ break;
+ }
+ }
+
+ /*
+ * Perform a best-effort search in the opposite direction from a bnobt
+ * allocation.
+ */
+ if (fbcur) {
+ error = xfs_alloc_walk_iter(args, acur, fbcur, fbinc, true,
+ args->mp->m_alloc_mxr[0], &i);
+ if (error)
+ return error;
+ }
+
+ if (acur->len)
+ *stat = 1;
+
+ return error;
+}

/*
* Deal with the case where only small freespaces remain. Either return the
@@ -814,6 +1251,113 @@ xfs_alloc_ag_vextent_small(
return error;
}

+/*
+ * Allocate a variable extent near bno in the allocation group agno.
+ * Extent's length (returned in len) will be between minlen and maxlen,
+ * and of the form k * prod + mod unless there's nothing that large.
+ * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
+ */
+STATIC int
+xfs_alloc_ag_vextent_near(
+ struct xfs_alloc_arg *args)
+{
+ struct xfs_alloc_cur acur = {0,};
+ int error;
+ int i;
+ xfs_agblock_t bno;
+ xfs_extlen_t len;
+
+ /* handle unitialized agbno range so caller doesn't have to */
+ if (!args->min_agbno && !args->max_agbno)
+ args->max_agbno = args->mp->m_sb.sb_agblocks - 1;
+ ASSERT(args->min_agbno <= args->max_agbno);
+
+ /* clamp agbno to the range if it's outside */
+ if (args->agbno < args->min_agbno)
+ args->agbno = args->min_agbno;
+ if (args->agbno > args->max_agbno)
+ args->agbno = args->max_agbno;
+
+restart:
+ error = xfs_alloc_cur_setup(args, &acur);
+ if (error) {
+ error = (error == -ENOSPC) ? 0 : error;
+ goto out;
+ }
+
+ /*
+ * The cntbt cursor points at the first maxlen or minlen extent. If it
+ * resides in the last block of the tree, scan the rest of the block.
+ * Otherwise run the optimized lookup search algorithm from the current
+ * location to the end of the tree.
+ */
+ if (xfs_btree_islastblock(acur.cnt, 0)) {
+ int j;
+
+ trace_xfs_alloc_cur_lastblock(args);
+ error = xfs_alloc_walk_iter(args, &acur, acur.cnt, true, false,
+ INT_MAX, &i);
+ if (error)
+ goto out;
+
+ /*
+ * If allocation fails, reset the cursor for a reverse minlen
+ * scan. cur_len doesn't change so look up the extent just
+ * before the starting point.
+ */
+ if (!i && acur.cur_len > args->minlen)
+ error = xfs_alloc_lookup_le(acur.cnt, 0, acur.cur_len, &j);
+ } else {
+ error = xfs_alloc_ag_vextent_lookup(args, &acur, &i);
+ }
+ if (error)
+ goto out;
+
+ /*
+ * Ignore locality and search backwards for the first suitable minlen
+ * extent. This fails if we run out of minlen extents.
+ */
+ if (!i && xfs_alloc_cur_active(acur.cnt)) {
+ trace_xfs_alloc_cur_reverse(args);
+ error = xfs_alloc_walk_iter(args, &acur, acur.cnt, false, true,
+ INT_MAX, &i);
+ if (error)
+ goto out;
+ }
+
+ if (!i) {
+ /* flush and retry if we found busy extents */
+ if (acur.busy) {
+ trace_xfs_alloc_ag_busy(args);
+ xfs_extent_busy_flush(args->mp, args->pag,
+ acur.busy_gen);
+ goto restart;
+ }
+
+ /*
+ * Try the AGFL as a last resort. Don't pass a cursor so this
+ * returns an AGFL block (i == 0) or nothing.
+ */
+ error = xfs_alloc_ag_vextent_small(args, NULL, &bno, &len, &i);
+ if (error)
+ goto out;
+ ASSERT(i == 0 || (i && len == 0));
+ trace_xfs_alloc_ag_noentry(args);
+
+ args->agbno = bno;
+ args->len = len;
+ goto out;
+ }
+
+ /* fix up btrees on a successful allocation */
+ error = xfs_alloc_cur_finish(args, &acur);
+out:
+ xfs_alloc_cur_close(&acur, error);
+ if (error)
+ trace_xfs_alloc_ag_error(args);
+ return error;
+}
+
/*
* Allocate a variable extent in the allocation group agno.
* Type and bno are used to determine where in the allocation group the
@@ -1001,503 +1545,6 @@ xfs_alloc_ag_vextent_exact(
return error;
}

-/*
- * Search the btree in a given direction via the search cursor and compare
- * the records found against the good extent we've already found.
- */
-STATIC int
-xfs_alloc_find_best_extent(
- struct xfs_alloc_arg *args, /* allocation argument structure */
- struct xfs_btree_cur **gcur, /* good cursor */
- struct xfs_btree_cur **scur, /* searching cursor */
- xfs_agblock_t gdiff, /* difference for search comparison */
- xfs_agblock_t *sbno, /* extent found by search */
- xfs_extlen_t *slen, /* extent length */
- xfs_agblock_t *sbnoa, /* aligned extent found by search */
- xfs_extlen_t *slena, /* aligned extent length */
- int dir) /* 0 = search right, 1 = search left */
-{
- xfs_agblock_t new;
- xfs_agblock_t sdiff;
- int error;
- int i;
- unsigned busy_gen;
-
- /* The good extent is perfect, no need to search. */
- if (!gdiff)
- goto out_use_good;
-
- /*
- * Look until we find a better one, run out of space or run off the end.
- */
- do {
- error = xfs_alloc_get_rec(*scur, sbno, slen, &i);
- if (error)
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- xfs_alloc_compute_aligned(args, *sbno, *slen,
- sbnoa, slena, &busy_gen);
-
- /*
- * The good extent is closer than this one.
- */
- if (!dir) {
- if (*sbnoa > args->max_agbno)
- goto out_use_good;
- if (*sbnoa >= args->agbno + gdiff)
- goto out_use_good;
- } else {
- if (*sbnoa < args->min_agbno)
- goto out_use_good;
- if (*sbnoa <= args->agbno - gdiff)
- goto out_use_good;
- }
-
- /*
- * Same distance, compare length and pick the best.
- */
- if (*slena >= args->minlen) {
- args->len = XFS_EXTLEN_MIN(*slena, args->maxlen);
- xfs_alloc_fix_len(args);
-
- sdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment,
- args->datatype, *sbnoa,
- *slena, &new);
-
- /*
- * Choose closer size and invalidate other cursor.
- */
- if (sdiff < gdiff)
- goto out_use_search;
- goto out_use_good;
- }
-
- if (!dir)
- error = xfs_btree_increment(*scur, 0, &i);
- else
- error = xfs_btree_decrement(*scur, 0, &i);
- if (error)
- goto error0;
- } while (i);
-
-out_use_good:
- xfs_btree_del_cursor(*scur, XFS_BTREE_NOERROR);
- *scur = NULL;
- return 0;
-
-out_use_search:
- xfs_btree_del_cursor(*gcur, XFS_BTREE_NOERROR);
- *gcur = NULL;
- return 0;
-
-error0:
- /* caller invalidates cursors */
- return error;
-}
-
-/*
- * Allocate a variable extent near bno in the allocation group agno.
- * Extent's length (returned in len) will be between minlen and maxlen,
- * and of the form k * prod + mod unless there's nothing that large.
- * Return the starting a.g. block, or NULLAGBLOCK if we can't do it.
- */
-STATIC int /* error */
-xfs_alloc_ag_vextent_near(
- xfs_alloc_arg_t *args) /* allocation argument structure */
-{
- xfs_btree_cur_t *bno_cur_gt; /* cursor for bno btree, right side */
- xfs_btree_cur_t *bno_cur_lt; /* cursor for bno btree, left side */
- xfs_btree_cur_t *cnt_cur; /* cursor for count btree */
- xfs_agblock_t gtbno; /* start bno of right side entry */
- xfs_agblock_t gtbnoa; /* aligned ... */
- xfs_extlen_t gtdiff; /* difference to right side entry */
- xfs_extlen_t gtlen; /* length of right side entry */
- xfs_extlen_t gtlena; /* aligned ... */
- xfs_agblock_t gtnew; /* useful start bno of right side */
- int error; /* error code */
- int i; /* result code, temporary */
- int j; /* result code, temporary */
- xfs_agblock_t ltbno; /* start bno of left side entry */
- xfs_agblock_t ltbnoa; /* aligned ... */
- xfs_extlen_t ltdiff; /* difference to left side entry */
- xfs_extlen_t ltlen; /* length of left side entry */
- xfs_extlen_t ltlena; /* aligned ... */
- xfs_agblock_t ltnew; /* useful start bno of left side */
- xfs_extlen_t rlen; /* length of returned extent */
- bool busy;
- unsigned busy_gen;
-#ifdef DEBUG
- /*
- * Randomly don't execute the first algorithm.
- */
- int dofirst; /* set to do first algorithm */
-
- dofirst = prandom_u32() & 1;
-#endif
-
- /* handle unitialized agbno range so caller doesn't have to */
- if (!args->min_agbno && !args->max_agbno)
- args->max_agbno = args->mp->m_sb.sb_agblocks - 1;
- ASSERT(args->min_agbno <= args->max_agbno);
-
- /* clamp agbno to the range if it's outside */
- if (args->agbno < args->min_agbno)
- args->agbno = args->min_agbno;
- if (args->agbno > args->max_agbno)
- args->agbno = args->max_agbno;
-
-restart:
- bno_cur_lt = NULL;
- bno_cur_gt = NULL;
- ltlen = 0;
- gtlena = 0;
- ltlena = 0;
- busy = false;
-
- /*
- * Get a cursor for the by-size btree.
- */
- cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
- args->agno, XFS_BTNUM_CNT);
-
- /*
- * See if there are any free extents as big as maxlen.
- */
- if ((error = xfs_alloc_lookup_ge(cnt_cur, 0, args->maxlen, &i)))
- goto error0;
- /*
- * If none, then pick up the last entry in the tree unless the
- * tree is empty.
- */
- if (!i) {
- if ((error = xfs_alloc_ag_vextent_small(args, cnt_cur, &ltbno,
- &ltlen, &i)))
- goto error0;
- if (i == 0 || ltlen == 0) {
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
- trace_xfs_alloc_near_noentry(args);
- return 0;
- }
- ASSERT(i == 1);
- }
- args->wasfromfl = 0;
-
- /*
- * First algorithm.
- * If the requested extent is large wrt the freespaces available
- * in this a.g., then the cursor will be pointing to a btree entry
- * near the right edge of the tree. If it's in the last btree leaf
- * block, then we just examine all the entries in that block
- * that are big enough, and pick the best one.
- * This is written as a while loop so we can break out of it,
- * but we never loop back to the top.
- */
- while (xfs_btree_islastblock(cnt_cur, 0)) {
- xfs_extlen_t bdiff;
- int besti=0;
- xfs_extlen_t blen=0;
- xfs_agblock_t bnew=0;
-
-#ifdef DEBUG
- if (dofirst)
- break;
-#endif
- /*
- * Start from the entry that lookup found, sequence through
- * all larger free blocks. If we're actually pointing at a
- * record smaller than maxlen, go to the start of this block,
- * and skip all those smaller than minlen.
- */
- if (ltlen || args->alignment > 1) {
- cnt_cur->bc_ptrs[0] = 1;
- do {
- if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno,
- &ltlen, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- if (ltlen >= args->minlen)
- break;
- if ((error = xfs_btree_increment(cnt_cur, 0, &i)))
- goto error0;
- } while (i);
- ASSERT(ltlen >= args->minlen);
- if (!i)
- break;
- }
- i = cnt_cur->bc_ptrs[0];
- for (j = 1, blen = 0, bdiff = 0;
- !error && j && (blen < args->maxlen || bdiff > 0);
- error = xfs_btree_increment(cnt_cur, 0, &j)) {
- /*
- * For each entry, decide if it's better than
- * the previous best entry.
- */
- if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- busy = xfs_alloc_compute_aligned(args, ltbno, ltlen,
- &ltbnoa, &ltlena, &busy_gen);
- if (ltlena < args->minlen)
- continue;
- if (ltbnoa < args->min_agbno || ltbnoa > args->max_agbno)
- continue;
- args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
- xfs_alloc_fix_len(args);
- ASSERT(args->len >= args->minlen);
- if (args->len < blen)
- continue;
- ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment, args->datatype, ltbnoa,
- ltlena, &ltnew);
- if (ltnew != NULLAGBLOCK &&
- (args->len > blen || ltdiff < bdiff)) {
- bdiff = ltdiff;
- bnew = ltnew;
- blen = args->len;
- besti = cnt_cur->bc_ptrs[0];
- }
- }
- /*
- * It didn't work. We COULD be in a case where
- * there's a good record somewhere, so try again.
- */
- if (blen == 0)
- break;
- /*
- * Point at the best entry, and retrieve it again.
- */
- cnt_cur->bc_ptrs[0] = besti;
- if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- 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.
- */
- args->agbno = bnew;
- ASSERT(bnew >= ltbno);
- ASSERT(bnew + blen <= ltbno + ltlen);
- /*
- * Set up a cursor for the by-bno tree.
- */
- bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp,
- args->agbp, args->agno, XFS_BTNUM_BNO);
- /*
- * Fix up the btree entries.
- */
- if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno,
- ltlen, bnew, blen, XFSA_FIXUP_CNT_OK)))
- goto error0;
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
- xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
-
- trace_xfs_alloc_near_first(args);
- return 0;
- }
- /*
- * Second algorithm.
- * Search in the by-bno tree to the left and to the right
- * simultaneously, until in each case we find a space big enough,
- * or run into the edge of the tree. When we run into the edge,
- * we deallocate that cursor.
- * If both searches succeed, we compare the two spaces and pick
- * the better one.
- * With alignment, it's possible for both to fail; the upper
- * level algorithm that picks allocation groups for allocations
- * is not supposed to do this.
- */
- /*
- * Allocate and initialize the cursor for the leftward search.
- */
- bno_cur_lt = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
- args->agno, XFS_BTNUM_BNO);
- /*
- * Lookup <= bno to find the leftward search's starting point.
- */
- if ((error = xfs_alloc_lookup_le(bno_cur_lt, args->agbno, args->maxlen, &i)))
- goto error0;
- if (!i) {
- /*
- * Didn't find anything; use this cursor for the rightward
- * search.
- */
- bno_cur_gt = bno_cur_lt;
- bno_cur_lt = NULL;
- }
- /*
- * Found something. Duplicate the cursor for the rightward search.
- */
- else if ((error = xfs_btree_dup_cursor(bno_cur_lt, &bno_cur_gt)))
- goto error0;
- /*
- * Increment the cursor, so we will point at the entry just right
- * of the leftward entry if any, or to the leftmost entry.
- */
- if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
- goto error0;
- if (!i) {
- /*
- * It failed, there are no rightward entries.
- */
- xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_NOERROR);
- bno_cur_gt = NULL;
- }
- /*
- * Loop going left with the leftward cursor, right with the
- * rightward cursor, until either both directions give up or
- * we find an entry at least as big as minlen.
- */
- do {
- if (bno_cur_lt) {
- if ((error = xfs_alloc_get_rec(bno_cur_lt, &ltbno, &ltlen, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- busy |= xfs_alloc_compute_aligned(args, ltbno, ltlen,
- &ltbnoa, &ltlena, &busy_gen);
- if (ltlena >= args->minlen && ltbnoa >= args->min_agbno)
- break;
- if ((error = xfs_btree_decrement(bno_cur_lt, 0, &i)))
- goto error0;
- if (!i || ltbnoa < args->min_agbno) {
- xfs_btree_del_cursor(bno_cur_lt,
- XFS_BTREE_NOERROR);
- bno_cur_lt = NULL;
- }
- }
- if (bno_cur_gt) {
- if ((error = xfs_alloc_get_rec(bno_cur_gt, &gtbno, &gtlen, &i)))
- goto error0;
- XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
- busy |= xfs_alloc_compute_aligned(args, gtbno, gtlen,
- &gtbnoa, &gtlena, &busy_gen);
- if (gtlena >= args->minlen && gtbnoa <= args->max_agbno)
- break;
- if ((error = xfs_btree_increment(bno_cur_gt, 0, &i)))
- goto error0;
- if (!i || gtbnoa > args->max_agbno) {
- xfs_btree_del_cursor(bno_cur_gt,
- XFS_BTREE_NOERROR);
- bno_cur_gt = NULL;
- }
- }
- } while (bno_cur_lt || bno_cur_gt);
-
- /*
- * Got both cursors still active, need to find better entry.
- */
- if (bno_cur_lt && bno_cur_gt) {
- if (ltlena >= args->minlen) {
- /*
- * Left side is good, look for a right side entry.
- */
- args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
- xfs_alloc_fix_len(args);
- ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment, args->datatype, ltbnoa,
- ltlena, &ltnew);
-
- error = xfs_alloc_find_best_extent(args,
- &bno_cur_lt, &bno_cur_gt,
- ltdiff, &gtbno, &gtlen,
- &gtbnoa, &gtlena,
- 0 /* search right */);
- } else {
- ASSERT(gtlena >= args->minlen);
-
- /*
- * Right side is good, look for a left side entry.
- */
- args->len = XFS_EXTLEN_MIN(gtlena, args->maxlen);
- xfs_alloc_fix_len(args);
- gtdiff = xfs_alloc_compute_diff(args->agbno, args->len,
- args->alignment, args->datatype, gtbnoa,
- gtlena, &gtnew);
-
- error = xfs_alloc_find_best_extent(args,
- &bno_cur_gt, &bno_cur_lt,
- gtdiff, &ltbno, &ltlen,
- &ltbnoa, &ltlena,
- 1 /* search left */);
- }
-
- if (error)
- goto error0;
- }
-
- /*
- * If we couldn't get anything, give up.
- */
- if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
-
- if (busy) {
- trace_xfs_alloc_near_busy(args);
- xfs_extent_busy_flush(args->mp, args->pag, busy_gen);
- goto restart;
- }
- trace_xfs_alloc_size_neither(args);
- args->agbno = NULLAGBLOCK;
- return 0;
- }
-
- /*
- * At this point we have selected a freespace entry, either to the
- * left or to the right. If it's on the right, copy all the
- * useful variables to the "left" set so we only have one
- * copy of this code.
- */
- if (bno_cur_gt) {
- bno_cur_lt = bno_cur_gt;
- bno_cur_gt = NULL;
- ltbno = gtbno;
- ltbnoa = gtbnoa;
- ltlen = gtlen;
- ltlena = gtlena;
- j = 1;
- } else
- j = 0;
-
- /*
- * Fix up the length and compute the useful address.
- */
- args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
- xfs_alloc_fix_len(args);
- rlen = args->len;
- (void)xfs_alloc_compute_diff(args->agbno, rlen, args->alignment,
- args->datatype, ltbnoa, ltlena, &ltnew);
- ASSERT(ltnew >= ltbno);
- ASSERT(ltnew + rlen <= ltbnoa + ltlena);
- ASSERT(ltnew + rlen <= be32_to_cpu(XFS_BUF_TO_AGF(args->agbp)->agf_length));
- ASSERT(ltnew >= args->min_agbno && ltnew <= args->max_agbno);
- args->agbno = ltnew;
-
- if ((error = xfs_alloc_fixup_trees(cnt_cur, bno_cur_lt, ltbno, ltlen,
- ltnew, rlen, XFSA_FIXUP_BNO_OK)))
- goto error0;
-
- if (j)
- trace_xfs_alloc_near_greater(args);
- else
- trace_xfs_alloc_near_lesser(args);
-
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
- xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_NOERROR);
- return 0;
-
- error0:
- trace_xfs_alloc_near_error(args);
- if (cnt_cur != NULL)
- xfs_btree_del_cursor(cnt_cur, XFS_BTREE_ERROR);
- if (bno_cur_lt != NULL)
- xfs_btree_del_cursor(bno_cur_lt, XFS_BTREE_ERROR);
- if (bno_cur_gt != NULL)
- xfs_btree_del_cursor(bno_cur_gt, XFS_BTREE_ERROR);
- return error;
-}
-
/*
* Allocate a variable extent anywhere in the allocation group agno.
* Extent's length (returned in len) will be between minlen and maxlen,
diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
index 8094b1920eef..a441a472da79 100644
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -1635,14 +1635,16 @@ DEFINE_EVENT(xfs_alloc_class, name, \
DEFINE_ALLOC_EVENT(xfs_alloc_exact_done);
DEFINE_ALLOC_EVENT(xfs_alloc_exact_notfound);
DEFINE_ALLOC_EVENT(xfs_alloc_exact_error);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_nominleft);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_first);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_greater);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_lesser);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_error);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_noentry);
-DEFINE_ALLOC_EVENT(xfs_alloc_near_busy);
-DEFINE_ALLOC_EVENT(xfs_alloc_size_neither);
+DEFINE_ALLOC_EVENT(xfs_alloc_ag_error);
+DEFINE_ALLOC_EVENT(xfs_alloc_ag_noentry);
+DEFINE_ALLOC_EVENT(xfs_alloc_ag_busy);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur_lastblock);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur_left);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur_right);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur_lookup);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur_lookup_done);
+DEFINE_ALLOC_EVENT(xfs_alloc_cur_reverse);
DEFINE_ALLOC_EVENT(xfs_alloc_size_noentry);
DEFINE_ALLOC_EVENT(xfs_alloc_size_nominleft);
DEFINE_ALLOC_EVENT(xfs_alloc_size_done);
@@ -1658,6 +1660,31 @@ DEFINE_ALLOC_EVENT(xfs_alloc_vextent_noagbp);
DEFINE_ALLOC_EVENT(xfs_alloc_vextent_loopfailed);
DEFINE_ALLOC_EVENT(xfs_alloc_vextent_allfailed);

+TRACE_EVENT(xfs_alloc_cur_check,
+ TP_PROTO(struct xfs_mount *mp, xfs_btnum_t btnum, xfs_agblock_t bno,
+ xfs_extlen_t len, xfs_extlen_t diff, bool new),
+ TP_ARGS(mp, btnum, bno, len, diff, new),
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(xfs_btnum_t, btnum)
+ __field(xfs_agblock_t, bno)
+ __field(xfs_extlen_t, len)
+ __field(xfs_extlen_t, diff)
+ __field(bool, new)
+ ),
+ TP_fast_assign(
+ __entry->dev = mp->m_super->s_dev;
+ __entry->btnum = btnum;
+ __entry->bno = bno;
+ __entry->len = len;
+ __entry->diff = diff;
+ __entry->new = new;
+ ),
+ TP_printk("dev %d:%d btnum %d bno 0x%x len 0x%x diff 0x%x new %d",
+ MAJOR(__entry->dev), MINOR(__entry->dev), __entry->btnum,
+ __entry->bno, __entry->len, __entry->diff, __entry->new)
+)
+
DECLARE_EVENT_CLASS(xfs_da_class,
TP_PROTO(struct xfs_da_args *args),
TP_ARGS(args),
--
2.20.1