Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
dm mpath: use double checked locking in fast path
Fast-path code biased toward lazy acknowledgement of bit being set
(primarily only for initialization). Multipath code is very retry
oriented so even if state is missed it'll recover.
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
+23
-9
+23
-9
drivers/md/dm-mpath.c
+23
-9
drivers/md/dm-mpath.c
···
128
128
#define MPATHF_PG_INIT_REQUIRED 5 /* pg_init needs calling? */
129
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#define MPATHF_PG_INIT_DELAY_RETRY 6 /* Delay pg_init retry? */
130
130
131
+
static bool mpath_double_check_test_bit(int MPATHF_bit, struct multipath *m)
132
+
{
133
+
bool r = test_bit(MPATHF_bit, &m->flags);
134
+
135
+
if (r) {
136
+
unsigned long flags;
137
+
spin_lock_irqsave(&m->lock, flags);
138
+
r = test_bit(MPATHF_bit, &m->flags);
139
+
spin_unlock_irqrestore(&m->lock, flags);
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+
}
141
+
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+
return r;
143
+
}
144
+
131
145
/*-----------------------------------------------
132
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* Allocation routines
133
147
*-----------------------------------------------*/
···
513
499
514
500
/* Do we need to select a new pgpath? */
515
501
pgpath = READ_ONCE(m->current_pgpath);
516
-
if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
502
+
if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
517
503
pgpath = choose_pgpath(m, nr_bytes);
518
504
519
505
if (!pgpath) {
···
521
507
return DM_MAPIO_DELAY_REQUEUE;
522
508
dm_report_EIO(m); /* Failed */
523
509
return DM_MAPIO_KILL;
524
-
} else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
525
-
test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
510
+
} else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
511
+
mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
526
512
pg_init_all_paths(m);
527
513
return DM_MAPIO_DELAY_REQUEUE;
528
514
}
···
612
598
613
599
/* Do we need to select a new pgpath? */
614
600
pgpath = READ_ONCE(m->current_pgpath);
615
-
if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
601
+
if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
616
602
pgpath = choose_pgpath(m, bio->bi_iter.bi_size);
617
603
618
604
if (!pgpath) {
···
623
609
}
624
610
spin_unlock_irqrestore(&m->lock, flags);
625
611
626
-
} else if (test_bit(MPATHF_QUEUE_IO, &m->flags) ||
627
-
test_bit(MPATHF_PG_INIT_REQUIRED, &m->flags)) {
612
+
} else if (mpath_double_check_test_bit(MPATHF_QUEUE_IO, m) ||
613
+
mpath_double_check_test_bit(MPATHF_PG_INIT_REQUIRED, m)) {
628
614
multipath_queue_bio(m, bio);
629
615
pg_init_all_paths(m);
630
616
return ERR_PTR(-EAGAIN);
···
875
861
struct request_queue *q = bdev_get_queue(bdev);
876
862
int r;
877
863
878
-
if (test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, &m->flags)) {
864
+
if (mpath_double_check_test_bit(MPATHF_RETAIN_ATTACHED_HW_HANDLER, m)) {
879
865
retain:
880
866
if (*attached_handler_name) {
881
867
/*
···
1981
1967
int r;
1982
1968
1983
1969
pgpath = READ_ONCE(m->current_pgpath);
1984
-
if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
1970
+
if (!pgpath || !mpath_double_check_test_bit(MPATHF_QUEUE_IO, m))
1985
1971
pgpath = choose_pgpath(m, 0);
1986
1972
1987
1973
if (pgpath) {
1988
-
if (!test_bit(MPATHF_QUEUE_IO, &m->flags)) {
1974
+
if (!mpath_double_check_test_bit(MPATHF_QUEUE_IO, m)) {
1989
1975
*bdev = pgpath->path.dev->bdev;
1990
1976
r = 0;
1991
1977
} else {