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xfs: improve handling of busy extents in the low-level allocator

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Currently we force the log and simply try again if we hit a busy extent,
but especially with online discard enabled it might take a while after
the log force for the busy extents to disappear, and we might have
already completed our second pass.

So instead we add a new waitqueue and a generation counter to the pag
structure so that we can do wakeups once we've removed busy extents,
and we replace the single retry with an unconditional one - after
all we hold the AGF buffer lock, so no other allocations or frees
can be racing with us in this AG.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2017-02-07 14:06:57 -08:00 • committed by Darrick J. Wong
parent 5e30c23d13
commit ebf5587261
5 changed files with 166 additions and 73 deletions
Download patch file Download diff file Expand all files Collapse all files

93
fs/xfs/libxfs/xfs_alloc.c
View file

@ -221,20 +221,22 @@ xfs_alloc_get_rec(
* Compute aligned version of the found extent.
* Takes alignment and min length into account.
*/
STATIC void
STATIC bool
xfs_alloc_compute_aligned(
xfs_alloc_arg_t *args, /* allocation argument structure */
xfs_agblock_t foundbno, /* starting block in found extent */
xfs_extlen_t foundlen, /* length in found extent */
xfs_agblock_t *resbno, /* result block number */
xfs_extlen_t *reslen) /* result length */
xfs_extlen_t *reslen, /* result length */
unsigned *busy_gen)
{
xfs_agblock_t bno;
xfs_extlen_t len;
xfs_agblock_t bno = foundbno;
xfs_extlen_t len = foundlen;
xfs_extlen_t diff;
bool busy;
/* Trim busy sections out of found extent */
xfs_extent_busy_trim(args, foundbno, foundlen, &bno, &len);
busy = xfs_extent_busy_trim(args, &bno, &len, busy_gen);
/*
* If we have a largish extent that happens to start before min_agbno,
@ -259,6 +261,8 @@ xfs_alloc_compute_aligned(
*resbno = bno;
*reslen = len;
}
return busy;
}
/*
@ -737,10 +741,11 @@ xfs_alloc_ag_vextent_exact(
int error;
xfs_agblock_t fbno; /* start block of found extent */
xfs_extlen_t flen; /* length of found extent */
xfs_agblock_t tbno; /* start block of trimmed extent */
xfs_extlen_t tlen; /* length of trimmed extent */
xfs_agblock_t tend; /* end block of trimmed extent */
xfs_agblock_t tbno; /* start block of busy extent */
xfs_extlen_t tlen; /* length of busy extent */
xfs_agblock_t tend; /* end block of busy extent */
int i; /* success/failure of operation */
unsigned busy_gen;
ASSERT(args->alignment == 1);
@ -773,7 +778,9 @@ xfs_alloc_ag_vextent_exact(
/*
* Check for overlapping busy extents.
*/
xfs_extent_busy_trim(args, fbno, flen, &tbno, &tlen);
tbno = fbno;
tlen = flen;
xfs_extent_busy_trim(args, &tbno, &tlen, &busy_gen);
/*
* Give up if the start of the extent is busy, or the freespace isn't
@ -853,6 +860,7 @@ xfs_alloc_find_best_extent(
xfs_agblock_t sdiff;
int error;
int i;
unsigned busy_gen;
/* The good extent is perfect, no need to search. */
if (!gdiff)
@ -866,7 +874,8 @@ xfs_alloc_find_best_extent(
if (error)
goto error0;
XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
xfs_alloc_compute_aligned(args, *sbno, *slen, sbnoa, slena);
xfs_alloc_compute_aligned(args, *sbno, *slen,
sbnoa, slena, &busy_gen);
/*
* The good extent is closer than this one.
@ -955,7 +964,8 @@ xfs_alloc_ag_vextent_near(
xfs_extlen_t ltlena; /* aligned ... */
xfs_agblock_t ltnew; /* useful start bno of left side */
xfs_extlen_t rlen; /* length of returned extent */
int forced = 0;
bool busy;
unsigned busy_gen;
#ifdef DEBUG
/*
* Randomly don't execute the first algorithm.
@ -982,6 +992,7 @@ restart:
ltlen = 0;
gtlena = 0;
ltlena = 0;
busy = false;
/*
* Get a cursor for the by-size btree.
@ -1064,8 +1075,8 @@ restart:
if ((error = xfs_alloc_get_rec(cnt_cur, &ltbno, &ltlen, &i)))
goto error0;
XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
xfs_alloc_compute_aligned(args, ltbno, ltlen,
&ltbnoa, &ltlena);
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)
@ -1183,8 +1194,8 @@ restart:
if ((error = xfs_alloc_get_rec(bno_cur_lt, &ltbno, &ltlen, &i)))
goto error0;
XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
xfs_alloc_compute_aligned(args, ltbno, ltlen,
&ltbnoa, &ltlena);
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)))
@ -1199,8 +1210,8 @@ restart:
if ((error = xfs_alloc_get_rec(bno_cur_gt, &gtbno, &gtlen, &i)))
goto error0;
XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
xfs_alloc_compute_aligned(args, gtbno, gtlen,
&gtbnoa, &gtlena);
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)))
@ -1261,9 +1272,9 @@ restart:
if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
if (!forced++) {
if (busy) {
trace_xfs_alloc_near_busy(args);
xfs_log_force(args->mp, XFS_LOG_SYNC);
xfs_extent_busy_flush(args->mp, args->pag, busy_gen);
goto restart;
}
trace_xfs_alloc_size_neither(args);
@ -1344,7 +1355,8 @@ xfs_alloc_ag_vextent_size(
int i; /* temp status variable */
xfs_agblock_t rbno; /* returned block number */
xfs_extlen_t rlen; /* length of returned extent */
int forced = 0;
bool busy;
unsigned busy_gen;
restart:
/*
@ -1353,6 +1365,7 @@ restart:
cnt_cur = xfs_allocbt_init_cursor(args->mp, args->tp, args->agbp,
args->agno, XFS_BTNUM_CNT);
bno_cur = NULL;
busy = false;
/*
* Look for an entry >= maxlen+alignment-1 blocks.
@ -1362,14 +1375,13 @@ restart:
goto error0;
/*
* If none or we have busy extents that we cannot allocate from, then
* we have to settle for a smaller extent. In the case that there are
* no large extents, this will return the last entry in the tree unless
* the tree is empty. In the case that there are only busy large
* extents, this will return the largest small extent unless there
* If none then we have to settle for a smaller extent. In the case that
* there are no large extents, this will return the last entry in the
* tree unless the tree is empty. In the case that there are only busy
* large extents, this will return the largest small extent unless there
* are no smaller extents available.
*/
if (!i || forced > 1) {
if (!i) {
error = xfs_alloc_ag_vextent_small(args, cnt_cur,
&fbno, &flen, &i);
if (error)
@ -1380,13 +1392,11 @@ restart:
return 0;
}
ASSERT(i == 1);
xfs_alloc_compute_aligned(args, fbno, flen, &rbno, &rlen);
busy = xfs_alloc_compute_aligned(args, fbno, flen, &rbno,
&rlen, &busy_gen);
} else {
/*
* Search for a non-busy extent that is large enough.
* If we are at low space, don't check, or if we fall of
* the end of the btree, turn off the busy check and
* restart.
*/
for (;;) {
error = xfs_alloc_get_rec(cnt_cur, &fbno, &flen, &i);
@ -1394,8 +1404,8 @@ restart:
goto error0;
XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
xfs_alloc_compute_aligned(args, fbno, flen,
&rbno, &rlen);
busy = xfs_alloc_compute_aligned(args, fbno, flen,
&rbno, &rlen, &busy_gen);
if (rlen >= args->maxlen)
break;
@ -1407,18 +1417,13 @@ restart:
/*
* Our only valid extents must have been busy.
* Make it unbusy by forcing the log out and
* retrying. If we've been here before, forcing
* the log isn't making the extents available,
* which means they have probably been freed in
* this transaction. In that case, we have to
* give up on them and we'll attempt a minlen
* allocation the next time around.
* retrying.
*/
xfs_btree_del_cursor(cnt_cur,
XFS_BTREE_NOERROR);
trace_xfs_alloc_size_busy(args);
if (!forced++)
xfs_log_force(args->mp, XFS_LOG_SYNC);
xfs_extent_busy_flush(args->mp,
args->pag, busy_gen);
goto restart;
}
}
@ -1454,8 +1459,8 @@ restart:
XFS_WANT_CORRUPTED_GOTO(args->mp, i == 1, error0);
if (flen < bestrlen)
break;
xfs_alloc_compute_aligned(args, fbno, flen,
&rbno, &rlen);
busy = xfs_alloc_compute_aligned(args, fbno, flen,
&rbno, &rlen, &busy_gen);
rlen = XFS_EXTLEN_MIN(args->maxlen, rlen);
XFS_WANT_CORRUPTED_GOTO(args->mp, rlen == 0 ||
(rlen <= flen && rbno + rlen <= fbno + flen),
@ -1484,10 +1489,10 @@ restart:
*/
args->len = rlen;
if (rlen < args->minlen) {
if (!forced++) {
if (busy) {
xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
trace_xfs_alloc_size_busy(args);
xfs_log_force(args->mp, XFS_LOG_SYNC);
xfs_extent_busy_flush(args->mp, args->pag, busy_gen);
goto restart;
}
goto out_nominleft;