io_uring: clean R_DISABLED startup mess

There are enough of problems with IORING_SETUP_R_DISABLED, including the
burden of checking and kicking off the SQO task all over the codebase --
for exit/cancel/etc.

Rework it, always start the thread but don't do submit unless the flag
is gone, that's much easier.

Signed-off-by: Pavel Begunkov <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 d4f018f..3f6db81 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6606,7 +6606,8 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
                if (!list_empty(&ctx->iopoll_list))
                        io_do_iopoll(ctx, &nr_events, 0);
 
-               if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)))
+               if (to_submit && likely(!percpu_ref_is_dying(&ctx->refs)) &&
+                   !(ctx->flags & IORING_SETUP_R_DISABLED))
                        ret = io_submit_sqes(ctx, to_submit);
                mutex_unlock(&ctx->uring_lock);
        }
@@ -7861,6 +7862,7 @@ static int io_sq_offload_create(struct io_ring_ctx *ctx,
                wake_up_new_task(tsk);
                if (ret)
                        goto err;
+               complete(&sqd->startup);
        } else if (p->flags & IORING_SETUP_SQ_AFF) {
                /* Can't have SQ_AFF without SQPOLL */
                ret = -EINVAL;
@@ -7873,15 +7875,6 @@ err:
        return ret;
 }
 
-static void io_sq_offload_start(struct io_ring_ctx *ctx)
-{
-       struct io_sq_data *sqd = ctx->sq_data;
-
-       ctx->flags &= ~IORING_SETUP_R_DISABLED;
-       if (ctx->flags & IORING_SETUP_SQPOLL)
-               complete(&sqd->startup);
-}
-
 static inline void __io_unaccount_mem(struct user_struct *user,
                                      unsigned long nr_pages)
 {
@@ -8742,11 +8735,6 @@ static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
        struct task_struct *task = current;
 
        if ((ctx->flags & IORING_SETUP_SQPOLL) && ctx->sq_data) {
-               /* never started, nothing to cancel */
-               if (ctx->flags & IORING_SETUP_R_DISABLED) {
-                       io_sq_offload_start(ctx);
-                       return;
-               }
                io_sq_thread_park(ctx->sq_data);
                task = ctx->sq_data->thread;
                if (task)
@@ -9449,9 +9437,6 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p,
        if (ret)
                goto err;
 
-       if (!(p->flags & IORING_SETUP_R_DISABLED))
-               io_sq_offload_start(ctx);
-
        memset(&p->sq_off, 0, sizeof(p->sq_off));
        p->sq_off.head = offsetof(struct io_rings, sq.head);
        p->sq_off.tail = offsetof(struct io_rings, sq.tail);
@@ -9668,7 +9653,9 @@ static int io_register_enable_rings(struct io_ring_ctx *ctx)
        if (ctx->restrictions.registered)
                ctx->restricted = 1;
 
-       io_sq_offload_start(ctx);
+       ctx->flags &= ~IORING_SETUP_R_DISABLED;
+       if (ctx->sq_data && wq_has_sleeper(&ctx->sq_data->wait))
+               wake_up(&ctx->sq_data->wait);
        return 0;
 }