io_uring/wait: make check for pending io consider cached task references

[PATCH] io_uring/wait: make check for pending io consider cached task references

Posted by Fiona Ebner 1 month, 2 weeks ago

The io_uring task's inflight count also includes the reservations for
task references from io_task_refs_refill(), not just in-flight
requests. Thus, pending requests are present if the inflight count is
larger than the number of cached references.

Co-developed-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
---
 io_uring/wait.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/io_uring/wait.c b/io_uring/wait.c
index 91df86ce0d18c..d9d4fe3b0f40c 100644
--- a/io_uring/wait.c
+++ b/io_uring/wait.c
@@ -48,7 +48,13 @@ static bool current_pending_io(void)
 
 	if (!tctx)
 		return false;
-	return percpu_counter_read_positive(&tctx->inflight);
+	/*
+	 * tctx->inflight also includes the reservations for task references
+	 * from io_task_refs_refill(), not just in-flight requests. Thus,
+	 * pending requests are present if the inflight count is larger than the
+	 * number of cached references.
+	 */
+	return percpu_counter_read_positive(&tctx->inflight) > tctx->cached_refs;
 }
 
 static enum hrtimer_restart io_cqring_timer_wakeup(struct hrtimer *timer)
-- 
2.47.3

Re: [PATCH] io_uring/wait: make check for pending io consider cached task references

Posted by Jens Axboe 1 month, 2 weeks ago

On 4/27/26 10:58 AM, Fiona Ebner wrote:
> The io_uring task's inflight count also includes the reservations for
> task references from io_task_refs_refill(), not just in-flight
> requests. Thus, pending requests are present if the inflight count is
> larger than the number of cached references.
> 
> Co-developed-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
> Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

Looks go to me! Just needs:

Cc: stable@vger.kernel.org
Fixes: 7b72d661f1f2 ("io_uring: gate iowait schedule on having pending requests")

tags added, I will do that. Thanks for debugging this and sending a fix.

-- 
Jens Axboe

Re: [PATCH] io_uring/wait: make check for pending io consider cached task references

Posted by Fiona Ebner 1 month, 2 weeks ago

Am 27.04.26 um 7:17 PM schrieb Jens Axboe:
> On 4/27/26 10:58 AM, Fiona Ebner wrote:
>> The io_uring task's inflight count also includes the reservations for
>> task references from io_task_refs_refill(), not just in-flight
>> requests. Thus, pending requests are present if the inflight count is
>> larger than the number of cached references.
>>
>> Co-developed-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
>> Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
>> Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
> 
> Looks go to me! Just needs:
> 
> Cc: stable@vger.kernel.org
> Fixes: 7b72d661f1f2 ("io_uring: gate iowait schedule on having pending requests")
> 
> tags added, I will do that. Thanks for debugging this and sending a fix.
> 

Thank you!