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authorUros Bizjak <ubizjak@gmail.com>2022-10-20 17:51:04 +0200
committerSong Liu <song@kernel.org>2022-11-14 09:35:50 -0800
commit9487a0f6855c1a28e4e39d41545cd19ed417c015 (patch)
tree09b4b8c272be00cdb285275f17b11119bb167643 /drivers/md/raid5-cache.c
parent3bd548e5b819b8c0f2c9085de775c5c7bff9052f (diff)
raid5-cache: use try_cmpxchg in r5l_wake_reclaim
Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in r5l_wake_reclaim. 86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails. There is no need to re-read the value in the loop. Note that the value from *ptr should be read using READ_ONCE to prevent the compiler from merging, refetching or reordering the read. No functional change intended. Cc: Song Liu <song@kernel.org> Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Song Liu <song@kernel.org>
Diffstat (limited to 'drivers/md/raid5-cache.c')
-rw-r--r--drivers/md/raid5-cache.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 832d8566e165..a63023aae21e 100644
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -1565,11 +1565,12 @@ void r5l_wake_reclaim(struct r5l_log *log, sector_t space)
if (!log)
return;
+
+ target = READ_ONCE(log->reclaim_target);
do {
- target = log->reclaim_target;
if (new < target)
return;
- } while (cmpxchg(&log->reclaim_target, target, new) != target);
+ } while (!try_cmpxchg(&log->reclaim_target, &target, new));
md_wakeup_thread(log->reclaim_thread);
}