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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-07-14 18:48:51 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2022-09-12 06:55:08 +0200 |
| commit | 38ace0d513d9d2556beca4d07102d25e9a73c53c (patch) | |
| tree | bf83fbde66aefcfb6b20fc16f1491fa3d32e62ff | |
| parent | buffer: use try_cmpxchg in discard_buffer (diff) | |
| download | linux-38ace0d513d9d2556beca4d07102d25e9a73c53c.tar.xz linux-38ace0d513d9d2556beca4d07102d25e9a73c53c.zip | |
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 <ubizjak@gmail.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | fs/aio.c | 9 |
1 files changed, 3 insertions, 6 deletions
@@ -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; } |