io_uring/rsrc: optimise io_rsrc_data refcounting

Every struct io_rsrc_node takes a struct io_rsrc_data reference, which
means all rsrc updates do 2 extra atomics. Replace atomics refcounting
with a int as it's all done under ->uring_lock.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e73c3d6820cf679532696d790b5b8fae23537213.1680576071.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index d4bca5e..603a783 100644 (file)
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -31,6 +31,11 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
 #define IORING_MAX_FIXED_FILES (1U << 20)
 #define IORING_MAX_REG_BUFFERS (1U << 14)
 
+static inline bool io_put_rsrc_data_ref(struct io_rsrc_data *rsrc_data)
+{
+       return !--rsrc_data->refs;
+}
+
 int __io_account_mem(struct user_struct *user, unsigned long nr_pages)
 {
        unsigned long page_limit, cur_pages, new_pages;
@@ -165,13 +170,13 @@ static void __io_rsrc_put_work(struct io_rsrc_node *ref_node)
        }
 
        io_rsrc_node_destroy(rsrc_data->ctx, ref_node);
-       if (atomic_dec_and_test(&rsrc_data->refs))
+       if (io_put_rsrc_data_ref(rsrc_data))
                complete(&rsrc_data->done);
 }
 
 void io_wait_rsrc_data(struct io_rsrc_data *data)
 {
-       if (data && !atomic_dec_and_test(&data->refs))
+       if (data && !io_put_rsrc_data_ref(data))
                wait_for_completion(&data->done);
 }
 
@@ -234,7 +239,7 @@ void io_rsrc_node_switch(struct io_ring_ctx *ctx,
                rsrc_node->rsrc_data = data_to_kill;
                list_add_tail(&rsrc_node->node, &ctx->rsrc_ref_list);
 
-               atomic_inc(&data_to_kill->refs);
+               data_to_kill->refs++;
                /* put master ref */
                io_put_rsrc_node(ctx, rsrc_node);
                ctx->rsrc_node = NULL;
@@ -267,8 +272,8 @@ __cold static int io_rsrc_ref_quiesce(struct io_rsrc_data *data,
                return ret;
        io_rsrc_node_switch(ctx, data);
 
-       /* kill initial ref, already quiesced if zero */
-       if (atomic_dec_and_test(&data->refs))
+       /* kill initial ref */
+       if (io_put_rsrc_data_ref(data))
                return 0;
 
        data->quiesce = true;
@@ -276,17 +281,19 @@ __cold static int io_rsrc_ref_quiesce(struct io_rsrc_data *data,
        do {
                ret = io_run_task_work_sig(ctx);
                if (ret < 0) {
-                       atomic_inc(&data->refs);
-                       /* wait for all works potentially completing data->done */
-                       reinit_completion(&data->done);
                        mutex_lock(&ctx->uring_lock);
+                       if (!data->refs) {
+                               ret = 0;
+                       } else {
+                               /* restore the master reference */
+                               data->refs++;
+                       }
                        break;
                }
-
                ret = wait_for_completion_interruptible(&data->done);
                if (!ret) {
                        mutex_lock(&ctx->uring_lock);
-                       if (atomic_read(&data->refs) <= 0)
+                       if (!data->refs)
                                break;
                        /*
                         * it has been revived by another thread while
@@ -361,6 +368,7 @@ __cold static int io_rsrc_data_alloc(struct io_ring_ctx *ctx,
        data->nr = nr;
        data->ctx = ctx;
        data->do_put = do_put;
+       data->refs = 1;
        if (utags) {
                ret = -EFAULT;
                for (i = 0; i < nr; i++) {
@@ -371,8 +379,6 @@ __cold static int io_rsrc_data_alloc(struct io_ring_ctx *ctx,
                                goto fail;
                }
        }
-
-       atomic_set(&data->refs, 1);
        init_completion(&data->done);
        *pdata = data;
        return 0;

diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
index cf24c3f..7ab9b2b 100644 (file)
--- a/io_uring/rsrc.h
+++ b/io_uring/rsrc.h
@@ -33,8 +33,8 @@ struct io_rsrc_data {
        u64                             **tags;
        unsigned int                    nr;
        rsrc_put_fn                     *do_put;
-       atomic_t                        refs;
        struct completion               done;
+       int                             refs;
        bool                            quiesce;
 };