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block: Use try_cmpxchg in update_io_ticks

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Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
update_io_ticks. x86 CMPXCHG instruction returns success in ZF flag,
so this change saves a compare after cmpxchg (and related
move instruction in front of cmpxchg).

No functional change intended.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20220712152741.7324-1-ubizjak@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Uros Bizjak 2022-07-12 17:27:41 +02:00 committed by Jens Axboe
parent f4b1e27db4
commit 939f9dd040
1 changed files with 1 additions and 1 deletions
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2
block/blk-core.c
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@ -943,7 +943,7 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end)
again:
stamp = READ_ONCE(part->bd_stamp);
if (unlikely(time_after(now, stamp))) {
if (likely(cmpxchg(&part->bd_stamp, stamp, now) == stamp))
if (likely(try_cmpxchg(&part->bd_stamp, &stamp, now)))
__part_stat_add(part, io_ticks, end ? now - stamp : 1);
}
if (part->bd_partno) {