[PATCH v2 06/13] io_uring/rsrc: kill rsrc_ref_lock

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

We use ->rsrc_ref_lock spinlock to protect ->rsrc_ref_list in
io_rsrc_node_ref_zero(). Now we removed pcpu refcounting, which means
io_rsrc_node_ref_zero() is not executed from the irq context as an RCU
callback anymore, and we also put it under ->uring_lock.
io_rsrc_node_switch(), which queues up nodes into the list, is also
protected by ->uring_lock, so we can safely get rid of ->rsrc_ref_lock.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
include/linux/io_uring_types.h | 2 +-
io_uring/io_uring.c | 1 -
io_uring/rsrc.c | 5 -----
3 files changed, 1 insertion(+), 7 deletions(-)

diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index a0a5b5964d3a..9492889f00c0 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -333,8 +333,8 @@ struct io_ring_ctx {
struct delayed_work rsrc_put_work;
struct callback_head rsrc_put_tw;
struct llist_head rsrc_put_llist;
+ /* protected by ->uring_lock */
struct list_head rsrc_ref_list;
- spinlock_t rsrc_ref_lock;

struct list_head io_buffers_pages;

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 36a76c7b34f0..764df5694d73 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -325,7 +325,6 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_LIST_HEAD(&ctx->defer_list);
INIT_LIST_HEAD(&ctx->timeout_list);
INIT_LIST_HEAD(&ctx->ltimeout_list);
- spin_lock_init(&ctx->rsrc_ref_lock);
INIT_LIST_HEAD(&ctx->rsrc_ref_list);
INIT_DELAYED_WORK(&ctx->rsrc_put_work, io_rsrc_put_work);
init_task_work(&ctx->rsrc_put_tw, io_rsrc_put_tw);
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 89e43e59b490..f3493b9d2bbb 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -209,11 +209,9 @@ void io_rsrc_node_ref_zero(struct io_rsrc_node *node)
__must_hold(&node->rsrc_data->ctx->uring_lock)
{
struct io_ring_ctx *ctx = node->rsrc_data->ctx;
- unsigned long flags;
bool first_add = false;
unsigned long delay = HZ;

- spin_lock_irqsave(&ctx->rsrc_ref_lock, flags);
node->done = true;

/* if we are mid-quiesce then do not delay */
@@ -229,7 +227,6 @@ void io_rsrc_node_ref_zero(struct io_rsrc_node *node)
list_del(&node->node);
first_add |= llist_add(&node->llist, &ctx->rsrc_put_llist);
}
- spin_unlock_irqrestore(&ctx->rsrc_ref_lock, flags);

if (!first_add)
return;
@@ -268,9 +265,7 @@ void io_rsrc_node_switch(struct io_ring_ctx *ctx,
struct io_rsrc_node *rsrc_node = ctx->rsrc_node;

rsrc_node->rsrc_data = data_to_kill;
- spin_lock_irq(&ctx->rsrc_ref_lock);
list_add_tail(&rsrc_node->node, &ctx->rsrc_ref_list);
- spin_unlock_irq(&ctx->rsrc_ref_lock);

atomic_inc(&data_to_kill->refs);
/* put master ref */
--
2.39.1