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From:   patrick wang <patrick.wang.shcn@gmail.com>
Date:   Wed, 6 Jul 2022 22:44:11 +0800
Message-ID: <CAGcnep_1QSdkNYqvgYC+ec2XVmqvG6rjZud-NfG22f_wQrJHKQ@mail.gmail.com>
Subject: Re: [PATCH] mm: percpu: use kmemleak_ignore_phys() instead of kmemleak_free()
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     dennis@kernel.org, tj@kernel.org, cl@linux.com,
        Catalin Marinas <catalin.marinas@arm.com>,
        "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
        linux-kernel@vger.kernel.org
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On Wed, Jul 6, 2022 at 5:20 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue,  5 Jul 2022 19:31:58 +0800 Patrick Wang <patrick.wang.shcn@gmail.com> wrote:
>
> > Kmemleak recently added a rbtree to store the objects
> > allocted with physical address. Those objects can't be
> > freed with kmemleak_free(). Use kmemleak_ignore_phys()
> > instead of kmemleak_free() for those objects.
>
> Thanks.  What are the user-visible runtime effects of this?

According to the comments, percpu allocations are tracked
by kmemleak separately. Kmemleak_free() was used to avoid
the unnecessary tracking. If kmemleak_free() fails, those
objects would be scanned by kmemleak, which is unnecessary
but shouldn't lead to other effects.

I didn't observe any anomaly without this commit on riscv
and arm64.

>
> And are we able to identify a commit for the Fixes: line?

0c24e061196c (mm: kmemleak: add rbtree and store physical
address for objects allocated with PA)
Current in mm-stable.

Thanks,
Patrick