Use atomic_long_try_cmpxchg instead of
atomic_long_cmpxchg (*ptr, old, new) == old in __io_account_mem.
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_long_try_cmpxchg implicitly assigns old *ptr value
to "old" when cmpxchg fails, enabling further code simplifications.
No functional change intended.
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a01ea49f3017..9f82904dcdae 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -10504,14 +10504,13 @@ static inline int __io_account_mem(struct user_struct *user,
/* Don't allow more pages than we can safely lock */
page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+ cur_pages = atomic_long_read(&user->locked_vm);
do {
- cur_pages = atomic_long_read(&user->locked_vm);
new_pages = cur_pages + nr_pages;
if (new_pages > page_limit)
return -ENOMEM;
- } while (atomic_long_cmpxchg(&user->locked_vm, cur_pages,
- new_pages) != cur_pages);
-
+ } while (!atomic_long_try_cmpxchg(&user->locked_vm,
+ &cur_pages, new_pages));
return 0;
}
--
2.35.3
