linux-kernel - [PATCH] io_uring: Don't require reinitable percpu

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Date:   Fri, 15 Jul 2022 19:45:01 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     axboe@...nel.dk
Cc:     asml.silence@...il.com, fam.zheng@...edance.com,
        io-uring@...r.kernel.org, linux-kernel@...r.kernel.org,
        roman.gushchin@...ux.dev, usama.arif@...edance.com
Subject: [PATCH] io_uring: Don't require reinitable percpu_ref

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>
---
 fs/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index a01ea49f3017..563f2266c674 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1911,7 +1911,7 @@ 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;
-- 
2.37.0