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| author | Uros Bizjak <ubizjak@gmail.com> | 2022-07-14 18:33:01 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-07-24 18:39:18 -0600 |
| commit | 4ccc6db0900fe337212b61650663a5dcedb69f25 (patch) | |
| tree | 48c46809c46a9461f9f33c3b1e12f6602fa168ba /io_uring/rsrc.c | |
| parent | 9bb66906f23e50d6db1e11f7498b72dfca1982a2 (diff) | |
| download | lwn-4ccc6db0900fe337212b61650663a5dcedb69f25.tar.gz lwn-4ccc6db0900fe337212b61650663a5dcedb69f25.zip | |
io_uring: Use atomic_long_try_cmpxchg in __io_account_mem
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@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring/rsrc.c')
| -rw-r--r-- | io_uring/rsrc.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c index 0250c13ae1cd..7f66b0e25674 100644 --- a/io_uring/rsrc.c +++ b/io_uring/rsrc.c @@ -56,14 +56,13 @@ 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; } |