[PATCH v2 12/13] io_uring/rsrc: optimise io_rsrc_data refcounting

Pavel Begunkov
2023-04-04T12:41:10Z

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>
---
io_uring/rsrc.c | 30 ++++++++++++++++++------------
io_uring/rsrc.h | 2 +-
2 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 95edc5f73204..74e13230fa0c 100644
--- 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 cf24c3fd701f..7ab9b2b2e757 100644
--- 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;
};

--
2.39.1