io_uring: thin down io_commit_cqring()

io_commit_cqring() is currently always under spinlock section, so it's
always better to keep it as slim as possible. Move
__io_commit_cqring_flush() out of it into ev_posted*(). If fast checks
do fail and this post-processing is required, we'll reacquire
->completion_lock, which is fine as we don't care about performance of
draining and offset timeouts.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/ec4e81fd720d3bc7bca8cb9152e080dad1a052f1.1647481208.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 31c625f..e69531c 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1779,20 +1779,21 @@ static __cold void io_flush_timeouts(struct io_ring_ctx *ctx)
        spin_unlock_irq(&ctx->timeout_lock);
 }
 
+static inline void io_commit_cqring(struct io_ring_ctx *ctx)
+{
+       /* order cqe stores with ring update */
+       smp_store_release(&ctx->rings->cq.tail, ctx->cached_cq_tail);
+}
+
 static __cold void __io_commit_cqring_flush(struct io_ring_ctx *ctx)
 {
+       spin_lock(&ctx->completion_lock);
        if (ctx->off_timeout_used)
                io_flush_timeouts(ctx);
        if (ctx->drain_active)
                io_queue_deferred(ctx);
-}
-
-static inline void io_commit_cqring(struct io_ring_ctx *ctx)
-{
-       if (unlikely(ctx->off_timeout_used || ctx->drain_active))
-               __io_commit_cqring_flush(ctx);
-       /* order cqe stores with ring update */
-       smp_store_release(&ctx->rings->cq.tail, ctx->cached_cq_tail);
+       io_commit_cqring(ctx);
+       spin_unlock(&ctx->completion_lock);
 }
 
 static inline bool io_sqring_full(struct io_ring_ctx *ctx)
@@ -1860,6 +1861,9 @@ out:
  */
 static inline void io_cqring_ev_posted(struct io_ring_ctx *ctx)
 {
+       if (unlikely(ctx->off_timeout_used || ctx->drain_active))
+               __io_commit_cqring_flush(ctx);
+
        /*
         * wake_up_all() may seem excessive, but io_wake_function() and
         * io_should_wake() handle the termination of the loop and only
@@ -1873,6 +1877,9 @@ static inline void io_cqring_ev_posted(struct io_ring_ctx *ctx)
 
 static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
 {
+       if (unlikely(ctx->off_timeout_used || ctx->drain_active))
+               __io_commit_cqring_flush(ctx);
+
        if (ctx->flags & IORING_SETUP_SQPOLL) {
                if (wq_has_sleeper(&ctx->cq_wait))
                        wake_up_all(&ctx->cq_wait);