io_uring: restructure submit sqes to_submit checks
Put an explicit check for number of requests to submit. First,
we can turn while into do-while and it generates better code, and second
that if can be cheaper, e.g. by using CPU flags after sub in
io_sqring_entries().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/5926baadd20c28feab7a5e1725fedf32e4553ff7.1632516769.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index bbb2a26..b8f60cf 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7225,16 +7225,19 @@ static const struct io_uring_sqe *io_get_sqe(struct io_ring_ctx *ctx)
static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
__must_hold(&ctx->uring_lock)
{
+ unsigned int entries = io_sqring_entries(ctx);
int submitted = 0;
+ if (!entries)
+ return 0;
/* make sure SQ entry isn't read before tail */
- nr = min3(nr, ctx->sq_entries, io_sqring_entries(ctx));
+ nr = min3(nr, ctx->sq_entries, entries);
if (!percpu_ref_tryget_many(&ctx->refs, nr))
return -EAGAIN;
io_get_task_refs(nr);
io_submit_state_start(&ctx->submit_state, nr);
- while (submitted < nr) {
+ do {
const struct io_uring_sqe *sqe;
struct io_kiocb *req;
@@ -7253,7 +7256,7 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr)
submitted++;
if (io_submit_sqe(ctx, req, sqe))
break;
- }
+ } while (submitted < nr);
if (unlikely(submitted != nr)) {
int ref_used = (submitted == -EAGAIN) ? 0 : submitted;
