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Sat, 27 Jun 2026 04:25:43 -0700 (PDT) From: Abd-Alrhman Masalkhi To: Chen Cheng , Chen Cheng , linux-raid@vger.kernel.org, yukuai@fygo.io Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] md: protect read mddev->recovery in md_sync_action() In-Reply-To: References: <20260627102909.141036-1-chencheng@fnnas.com> Date: Sat, 27 Jun 2026 13:25:42 +0200 Message-ID: Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Hi Chen, On Sat, Jun 27, 2026 at 18:52 +0800, Chen Cheng wrote: > =E5=9C=A8 2026/6/27 18:46, Abd-Alrhman Masalkhi =E5=86=99=E9=81=93: >> On Sat, Jun 27, 2026 at 18:29 +0800, Chen Cheng wrote: >>> From: Chen Cheng >>> >>> md_sync_action() read mddev->recovery in lockless path, use READ_ONCE() >>> instead of u64 plain read. >>> >> unisgned long is not always u64... >> I can not see what it fixes, is this just to silence KCSAN? If so, >> please say so in the commit message. > > I need to find KCSAN report , I lost this one, but I think it's easy to=20 > find locklessly path to call md_sync_action(), so. READ_ONCE is need. > Thanks. Adding the KCSAN report would be helpful. >>=20 >>> Fixes: e792a4c2156a3 ("md: add new helpers for sync_action") >>> >>> Signed-off-by: Chen Cheng >>> --- >>> drivers/md/md.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/md/md.c b/drivers/md/md.c >>> index c5c50640b684..f4415c1a79d9 100644 >>> --- a/drivers/md/md.c >>> +++ b/drivers/md/md.c >>> @@ -5074,11 +5074,11 @@ static enum sync_action md_get_active_sync_acti= on(struct mddev *mddev) >>> return is_recover ? ACTION_RECOVER : ACTION_IDLE; >>> } >>>=20=20=20 >>> enum sync_action md_sync_action(struct mddev *mddev) >>> { >>> - unsigned long recovery =3D mddev->recovery; >>> + unsigned long recovery =3D READ_ONCE(mddev->recovery); >>> enum sync_action active_action; >>>=20=20=20 >>> /* >>> * frozen has the highest priority, means running sync_thread will be >>> * stopped immediately, and no new sync_thread can start. >>> --=20 >>> 2.54.0 >>> >>=20 > --=20 Best Regards, Abd-Alrhman