rebase patches on top of Ubuntu-5.11.0-34.36

[pve-kernel.git] / patches / kernel / 0007-io_uring-don-t-block-level-reissue-off-completion-pa.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Fabian Ebner <f.ebner@proxmox.com>
Date: Wed, 28 Jul 2021 08:55:31 +0200
Subject: [PATCH] io_uring: don't block level reissue off completion path

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.

Upstream mail:
https://lore.kernel.org/io-uring/20210727165811.284510-3-axboe@kernel.dk/T/#u

Originally-by: Jens Axboe <axboe@kernel.dk>
[backport]
Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>
---
 fs/io_uring.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a0d42aea3aa1..ce5cf51a5667 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2731,6 +2731,13 @@ static bool io_rw_reissue(struct io_kiocb *req, long res)
 	if (percpu_ref_is_dying(&req->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;
+
 	lockdep_assert_held(&req->ctx->uring_lock);
 
 	ret = io_sq_thread_acquire_mm_files(req->ctx, req);