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locking/barriers: Convert users of lockless_dereference() to READ_ONCE()

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READ_ONCE() now has an implicit smp_read_barrier_depends() call, so it
can be used instead of lockless_dereference() without any change in
semantics.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1508840570-22169-4-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Will Deacon
2017-10-24 11:22:48 +01:00
committed by Ingo Molnar
parent 76ebbe78f7
commit 506458efaf
13 changed files with 27 additions and 27 deletions
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20
drivers/md/dm-mpath.c
View File

@@ -366,7 +366,7 @@ static struct pgpath *choose_path_in_pg(struct multipath *m,
pgpath = path_to_pgpath(path);
if (unlikely(lockless_dereference(m->current_pg) != pg)) {
if (unlikely(READ_ONCE(m->current_pg) != pg)) {
/* Only update current_pgpath if pg changed */
spin_lock_irqsave(&m->lock, flags);
m->current_pgpath = pgpath;
@@ -390,7 +390,7 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
}
/* Were we instructed to switch PG? */
if (lockless_dereference(m->next_pg)) {
if (READ_ONCE(m->next_pg)) {
spin_lock_irqsave(&m->lock, flags);
pg = m->next_pg;
if (!pg) {
@@ -406,7 +406,7 @@ static struct pgpath *choose_pgpath(struct multipath *m, size_t nr_bytes)
/* Don't change PG until it has no remaining paths */
check_current_pg:
pg = lockless_dereference(m->current_pg);
pg = READ_ONCE(m->current_pg);
if (pg) {
pgpath = choose_path_in_pg(m, pg, nr_bytes);
if (!IS_ERR_OR_NULL(pgpath))
@@ -473,7 +473,7 @@ static int multipath_clone_and_map(struct dm_target *ti, struct request *rq,
struct request *clone;
/* Do we need to select a new pgpath? */
pgpath = lockless_dereference(m->current_pgpath);
pgpath = READ_ONCE(m->current_pgpath);
if (!pgpath || !test_bit(MPATHF_QUEUE_IO, &m->flags))
pgpath = choose_pgpath(m, nr_bytes);
@@ -535,7 +535,7 @@ static int __multipath_map_bio(struct multipath *m, struct bio *bio, struct dm_m
bool queue_io;
/* Do we need to select a new pgpath? */
pgpath = lockless_dereference(m->current_pgpath);
pgpath = READ_ONCE(m->current_pgpath);
queue_io = test_bit(MPATHF_QUEUE_IO, &m->flags);
if (!pgpath || !queue_io)
pgpath = choose_pgpath(m, nr_bytes);
@@ -1804,7 +1804,7 @@ static int multipath_prepare_ioctl(struct dm_target *ti,
struct pgpath *current_pgpath;
int r;
current_pgpath = lockless_dereference(m->current_pgpath);
current_pgpath = READ_ONCE(m->current_pgpath);
if (!current_pgpath)
current_pgpath = choose_pgpath(m, 0);
@@ -1826,7 +1826,7 @@ static int multipath_prepare_ioctl(struct dm_target *ti,
}
if (r == -ENOTCONN) {
if (!lockless_dereference(m->current_pg)) {
if (!READ_ONCE(m->current_pg)) {
/* Path status changed, redo selection */
(void) choose_pgpath(m, 0);
}
@@ -1895,9 +1895,9 @@ static int multipath_busy(struct dm_target *ti)
return (m->queue_mode != DM_TYPE_MQ_REQUEST_BASED);
/* Guess which priority_group will be used at next mapping time */
pg = lockless_dereference(m->current_pg);
next_pg = lockless_dereference(m->next_pg);
if (unlikely(!lockless_dereference(m->current_pgpath) && next_pg))
pg = READ_ONCE(m->current_pg);
next_pg = READ_ONCE(m->next_pg);
if (unlikely(!READ_ONCE(m->current_pgpath) && next_pg))
pg = next_pg;
if (!pg) {