linux-kernel - [PATCH 5.19 0295/1157] io_uring: Dont require reinitable percpu

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Message-Id: <20220815180451.432936539@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 19:54:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Michal Koutný <mkoutny@...e.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Jens Axboe <axboe@...nel.dk>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.19 0295/1157] io_uring: Dont require reinitable percpu_ref

From: Michal Koutný <mkoutny@...e.com>

[ Upstream commit 48904229928d941ce1db181b991948387ab463cd ]

The commit 8bb649ee1da3 ("io_uring: remove ring quiesce for
io_uring_register") removed the worklow relying on reinit/resurrection
of the percpu_ref, hence, initialization with that requested is a relic.

This is based on code review, this causes no real bug (and theoretically
can't). Technically it's a revert of commit 214828962dea ("io_uring:
initialize percpu refcounters using PERCU_REF_ALLOW_REINIT") but since
the flag omission is now justified, I'm not making this a revert.

Fixes: 8bb649ee1da3 ("io_uring: remove ring quiesce for io_uring_register")
Signed-off-by: Michal Koutný <mkoutny@...e.com>
Acked-by: Roman Gushchin <roman.gushchin@...ux.dev>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 io_uring/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index f429b68d1fc2..27ce532c6c8d 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1701,7 +1701,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
 	ctx->dummy_ubuf->ubuf = -1UL;
 
 	if (percpu_ref_init(&ctx->refs, io_ring_ctx_ref_free,
-			    PERCPU_REF_ALLOW_REINIT, GFP_KERNEL))
+			    0, GFP_KERNEL))
 		goto err;
 
 	ctx->flags = p->flags;
-- 
2.35.1