io_uring: use single linked list for iopoll

Use single linked lists for keeping iopoll requests, takes less space,
may be faster, but mostly will be of benefit for further patches.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/314033676b100cd485518c3bc55e1b95a0dcd71f.1632516769.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io-wq.h b/fs/io-wq.h
index c870062..87ba6a7 100644 (file)
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -32,6 +32,9 @@ struct io_wq_work_list {
 #define wq_list_for_each(pos, prv, head)                       \
        for (pos = (head)->first, prv = NULL; pos; prv = pos, pos = (pos)->next)
 
+#define wq_list_for_each_resume(pos, prv)                      \
+       for (; pos; prv = pos, pos = (pos)->next)
+
 #define wq_list_empty(list)    (READ_ONCE((list)->first) == NULL)
 #define INIT_WQ_LIST(list)     do {                            \
        (list)->first = NULL;                                   \

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 0e46ed6..fac1d03 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -412,7 +412,7 @@ struct io_ring_ctx {
                 * For SQPOLL, only the single threaded io_sq_thread() will
                 * manipulate the list, hence no extra locking is needed there.
                 */
-               struct list_head        iopoll_list;
+               struct io_wq_work_list  iopoll_list;
                struct hlist_head       *cancel_hash;
                unsigned                cancel_hash_bits;
                bool                    poll_multi_queue;
@@ -1309,7 +1309,7 @@ static struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
        init_waitqueue_head(&ctx->cq_wait);
        spin_lock_init(&ctx->completion_lock);
        spin_lock_init(&ctx->timeout_lock);
-       INIT_LIST_HEAD(&ctx->iopoll_list);
+       INIT_WQ_LIST(&ctx->iopoll_list);
        INIT_LIST_HEAD(&ctx->defer_list);
        INIT_LIST_HEAD(&ctx->timeout_list);
        INIT_LIST_HEAD(&ctx->ltimeout_list);
@@ -2441,15 +2441,9 @@ static void io_iopoll_complete(struct io_ring_ctx *ctx, struct list_head *done)
        io_req_free_batch_finish(ctx, &rb);
 }
 
-/* same as "continue" but starts from the pos, not next to it */
-#define list_for_each_entry_safe_resume(pos, n, head, member)          \
-       for (n = list_next_entry(pos, member);                          \
-            !list_entry_is_head(pos, head, member);                    \
-            pos = n, n = list_next_entry(n, member))
-
 static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
 {
-       struct io_kiocb *req, *tmp;
+       struct io_wq_work_node *pos, *start, *prev;
        unsigned int poll_flags = BLK_POLL_NOSLEEP;
        DEFINE_IO_COMP_BATCH(iob);
        int nr_events = 0;
@@ -2462,7 +2456,8 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
        if (ctx->poll_multi_queue || force_nonspin)
                poll_flags |= BLK_POLL_ONESHOT;
 
-       list_for_each_entry(req, &ctx->iopoll_list, inflight_entry) {
+       wq_list_for_each(pos, start, &ctx->iopoll_list) {
+               struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
                struct kiocb *kiocb = &req->rw.kiocb;
                int ret;
 
@@ -2488,14 +2483,20 @@ static int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
 
        if (!rq_list_empty(iob.req_list))
                iob.complete(&iob);
-       list_for_each_entry_safe_resume(req, tmp, &ctx->iopoll_list,
-                                       inflight_entry) {
+       else if (!pos)
+               return 0;
+
+       prev = start;
+       wq_list_for_each_resume(pos, prev) {
+               struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
+
                if (!READ_ONCE(req->iopoll_completed))
                        break;
-               list_move_tail(&req->inflight_entry, &done);
+               list_add_tail(&req->inflight_entry, &done);
                nr_events++;
        }
 
+       wq_list_cut(&ctx->iopoll_list, prev, start);
        if (nr_events)
                io_iopoll_complete(ctx, &done);
        return nr_events;
@@ -2511,7 +2512,7 @@ static void io_iopoll_try_reap_events(struct io_ring_ctx *ctx)
                return;
 
        mutex_lock(&ctx->uring_lock);
-       while (!list_empty(&ctx->iopoll_list)) {
+       while (!wq_list_empty(&ctx->iopoll_list)) {
                /* let it sleep and repeat later if can't complete a request */
                if (io_do_iopoll(ctx, true) == 0)
                        break;
@@ -2560,7 +2561,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
                 * forever, while the workqueue is stuck trying to acquire the
                 * very same mutex.
                 */
-               if (list_empty(&ctx->iopoll_list)) {
+               if (wq_list_empty(&ctx->iopoll_list)) {
                        u32 tail = ctx->cached_cq_tail;
 
                        mutex_unlock(&ctx->uring_lock);
@@ -2569,7 +2570,7 @@ static int io_iopoll_check(struct io_ring_ctx *ctx, long min)
 
                        /* some requests don't go through iopoll_list */
                        if (tail != ctx->cached_cq_tail ||
-                           list_empty(&ctx->iopoll_list))
+                           wq_list_empty(&ctx->iopoll_list))
                                break;
                }
                ret = io_do_iopoll(ctx, !min);
@@ -2729,14 +2730,13 @@ static void io_iopoll_req_issued(struct io_kiocb *req)
         * how we do polling eventually, not spinning if we're on potentially
         * different devices.
         */
-       if (list_empty(&ctx->iopoll_list)) {
+       if (wq_list_empty(&ctx->iopoll_list)) {
                ctx->poll_multi_queue = false;
        } else if (!ctx->poll_multi_queue) {
                struct io_kiocb *list_req;
 
-               list_req = list_first_entry(&ctx->iopoll_list, struct io_kiocb,
-                                               inflight_entry);
-
+               list_req = container_of(ctx->iopoll_list.first, struct io_kiocb,
+                                       comp_list);
                if (list_req->file != req->file)
                        ctx->poll_multi_queue = true;
        }
@@ -2746,9 +2746,9 @@ static void io_iopoll_req_issued(struct io_kiocb *req)
         * it to the front so we find it first.
         */
        if (READ_ONCE(req->iopoll_completed))
-               list_add(&req->inflight_entry, &ctx->iopoll_list);
+               wq_list_add_head(&req->comp_list, &ctx->iopoll_list);
        else
-               list_add_tail(&req->inflight_entry, &ctx->iopoll_list);
+               wq_list_add_tail(&req->comp_list, &ctx->iopoll_list);
 
        if (unlikely(in_async)) {
                /*
@@ -7322,14 +7322,14 @@ static int __io_sq_thread(struct io_ring_ctx *ctx, bool cap_entries)
        if (cap_entries && to_submit > IORING_SQPOLL_CAP_ENTRIES_VALUE)
                to_submit = IORING_SQPOLL_CAP_ENTRIES_VALUE;
 
-       if (!list_empty(&ctx->iopoll_list) || to_submit) {
+       if (!wq_list_empty(&ctx->iopoll_list) || to_submit) {
                const struct cred *creds = NULL;
 
                if (ctx->sq_creds != current_cred())
                        creds = override_creds(ctx->sq_creds);
 
                mutex_lock(&ctx->uring_lock);
-               if (!list_empty(&ctx->iopoll_list))
+               if (!wq_list_empty(&ctx->iopoll_list))
                        io_do_iopoll(ctx, true);
 
                /*
@@ -7407,7 +7407,7 @@ static int io_sq_thread(void *data)
                list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) {
                        int ret = __io_sq_thread(ctx, cap_entries);
 
-                       if (!sqt_spin && (ret > 0 || !list_empty(&ctx->iopoll_list)))
+                       if (!sqt_spin && (ret > 0 || !wq_list_empty(&ctx->iopoll_list)))
                                sqt_spin = true;
                }
                if (io_run_task_work())
@@ -7428,7 +7428,7 @@ static int io_sq_thread(void *data)
                                io_ring_set_wakeup_flag(ctx);
 
                                if ((ctx->flags & IORING_SETUP_IOPOLL) &&
-                                   !list_empty_careful(&ctx->iopoll_list)) {
+                                   !wq_list_empty(&ctx->iopoll_list)) {
                                        needs_sched = false;
                                        break;
                                }
@@ -9583,7 +9583,7 @@ static void io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
                /* SQPOLL thread does its own polling */
                if ((!(ctx->flags & IORING_SETUP_SQPOLL) && cancel_all) ||
                    (ctx->sq_data && ctx->sq_data->thread == current)) {
-                       while (!list_empty_careful(&ctx->iopoll_list)) {
+                       while (!wq_list_empty(&ctx->iopoll_list)) {
                                io_iopoll_try_reap_events(ctx);
                                ret = true;
                        }