From: Song Liu <song@kernel.org>
To: Xiao Ni <xni@redhat.com>
Cc: Nigel Croxon <ncroxon@redhat.com>,
linux-raid <linux-raid@vger.kernel.org>,
Guoqing Jiang <guoqing.jiang@linux.dev>
Subject: Re: [PATCH v2] md/raid10: Remove rcu_dereference when it doesn't need rcu lock to protect
Date: Thu, 26 Aug 2021 09:18:11 -0700 [thread overview]
Message-ID: <CAPhsuW7dZXX2i-3pBMWX0C5q+RBrmCuMUz=6_KkKYPu3USQBhQ@mail.gmail.com> (raw)
In-Reply-To: <CAPhsuW73qcuf-a=ENW+f3ecb548uL2zHxir7dYixrnz5838gZw@mail.gmail.com>
On Fri, Aug 20, 2021 at 5:31 PM Song Liu <song@kernel.org> wrote:
>
> On Tue, Aug 17, 2021 at 10:58 PM Xiao Ni <xni@redhat.com> wrote:
> >
> > One warning message is triggered like this:
> > [ 695.110751] =============================
> > [ 695.131439] WARNING: suspicious RCU usage
> > [ 695.151389] 4.18.0-319.el8.x86_64+debug #1 Not tainted
> > [ 695.174413] -----------------------------
> > [ 695.192603] drivers/md/raid10.c:1776 suspicious
> > rcu_dereference_check() usage!
> > [ 695.225107] other info that might help us debug this:
> > [ 695.260940] rcu_scheduler_active = 2, debug_locks = 1
> > [ 695.290157] no locks held by mkfs.xfs/10186.
> >
> > In the first loop of function raid10_handle_discard. It already
> > determines which disk need to handle discard request and add the
> > rdev reference count rdev->nr_pending. So the conf->mirrors will
> > not change until all bios come back from underlayer disks. It
> > doesn't need to use rcu_dereference to get rdev.
> >
> > Fixes: d30588b2731f ('md/raid10: improve raid10 discard request')
> > Signed-off-by: Xiao Ni <xni@redhat.com>
> > Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
>
> Applied to md-fixes. Thanks!
Moved to md-next as we are too close to 5.14 release.
Thanks,
Song
prev parent reply other threads:[~2021-08-26 16:18 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 5:57 [PATCH v2] md/raid10: Remove rcu_dereference when it doesn't need rcu lock to protect Xiao Ni
2021-08-21 0:31 ` Song Liu
2021-08-26 16:18 ` Song Liu [this message]
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