This is a note to let you know that I've just added the patch titled
io_uring: fix bug in slow unregistering of nodes
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
io_uring-fix-bug-in-slow-unregistering-of-nodes.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 17fedcb20213ce347eec38e133cebfa9f200991e
Author: Dylan Yudaken <dylany@xxxxxx>
Date: Fri Jan 21 04:38:56 2022 -0800
io_uring: fix bug in slow unregistering of nodes
[ Upstream commit b36a2050040b2d839bdc044007cdd57101d7f881 ]
In some cases io_rsrc_ref_quiesce will call io_rsrc_node_switch_start,
and then immediately flush the delayed work queue &ctx->rsrc_put_work.
However the percpu_ref_put does not immediately destroy the node, it
will be called asynchronously via RCU. That ends up with
io_rsrc_node_ref_zero only being called after rsrc_put_work has been
flushed, and so the process ends up sleeping for 1 second unnecessarily.
This patch executes the put code immediately if we are busy
quiescing.
Fixes: 4a38aed2a0a7 ("io_uring: batch reap of dead file registrations")
Signed-off-by: Dylan Yudaken <dylany@xxxxxx>
Link: https://lore.kernel.org/r/20220121123856.3557884-1-dylany@xxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index f713b91537f41..993913c585fbf 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -7718,10 +7718,15 @@ static void io_rsrc_node_ref_zero(struct percpu_ref *ref)
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 */
+ if (node->rsrc_data->quiesce)
+ delay = 0;
+
while (!list_empty(&ctx->rsrc_ref_list)) {
node = list_first_entry(&ctx->rsrc_ref_list,
struct io_rsrc_node, node);
@@ -7734,7 +7739,7 @@ static void io_rsrc_node_ref_zero(struct percpu_ref *ref)
spin_unlock_irqrestore(&ctx->rsrc_ref_lock, flags);
if (first_add)
- mod_delayed_work(system_wq, &ctx->rsrc_put_work, HZ);
+ mod_delayed_work(system_wq, &ctx->rsrc_put_work, delay);
}
static struct io_rsrc_node *io_rsrc_node_alloc(struct io_ring_ctx *ctx)
