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From: Jens Axboe <[email protected]>
To: [email protected]
Cc: [email protected], Jens Axboe <[email protected]>,
	[email protected]
Subject: [PATCH 2/2] io_uring: don't block level reissue off completion path
Date: Tue, 27 Jul 2021 10:58:11 -0600	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Some setups, like SCSI, can throw spurious -EAGAIN off the softirq
completion path. Normally we expect this to happen inline as part
of submission, but apparently SCSI has a weird corner case where it
can happen as part of normal completions.

This should be solved by having the -EAGAIN bubble back up the stack
as part of submission, but previous attempts at this failed and we're
not just quite there yet. Instead we currently use REQ_F_REISSUE to
handle this case.

For now, catch it in io_rw_should_reissue() and prevent a reissue
from a bogus path.

Cc: [email protected]
Reported-by: Fabian Ebner <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>
---
 fs/io_uring.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6ba101cd4661..83f67d33bf67 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2447,6 +2447,12 @@ static bool io_rw_should_reissue(struct io_kiocb *req)
 	 */
 	if (percpu_ref_is_dying(&ctx->refs))
 		return false;
+	/*
+	 * Play it safe and assume not safe to re-import and reissue if we're
+	 * not in the original thread group (or in task context).
+	 */
+	if (!same_thread_group(req->task, current) || !in_task())
+		return false;
 	return true;
 }
 #else
-- 
2.32.0


  parent reply	other threads:[~2021-07-27 16:58 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-27 16:58 [PATCH 0/2] Further async re-queue tightening/fix Jens Axboe
2021-07-27 16:58 ` [PATCH 1/2] io_uring: always reissue from task_work context Jens Axboe
2021-07-27 16:58 ` Jens Axboe [this message]
2021-07-28  9:26   ` [PATCH 2/2] io_uring: don't block level reissue off completion path Fabian Ebner
2021-07-28 13:23     ` Jens Axboe
2021-07-29  6:50       ` Fabian Ebner

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