From 38ace0d513d9d2556beca4d07102d25e9a73c53c Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Thu, 14 Jul 2022 18:48:51 +0200 Subject: aio: use atomic_try_cmpxchg in __get_reqs_available Use atomic_try_cmpxchg instead of atomic_cmpxchg (*ptr, old, new) == old in __get_reqs_available. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, atomic_try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg fails, enabling further code simplifications. No functional change intended. Link: https://lkml.kernel.org/r/20220714164851.3055-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak Cc: Benjamin LaHaise Cc: Alexander Viro Signed-off-by: Andrew Morton --- fs/aio.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) (limited to 'fs/aio.c') diff --git a/fs/aio.c b/fs/aio.c index 606613e9d1f4..5b2ff20ad322 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -951,16 +951,13 @@ static bool __get_reqs_available(struct kioctx *ctx) local_irq_save(flags); kcpu = this_cpu_ptr(ctx->cpu); if (!kcpu->reqs_available) { - int old, avail = atomic_read(&ctx->reqs_available); + int avail = atomic_read(&ctx->reqs_available); do { if (avail < ctx->req_batch) goto out; - - old = avail; - avail = atomic_cmpxchg(&ctx->reqs_available, - avail, avail - ctx->req_batch); - } while (avail != old); + } while (!atomic_try_cmpxchg(&ctx->reqs_available, + &avail, avail - ctx->req_batch)); kcpu->reqs_available += ctx->req_batch; } -- cgit