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From: Roman Gushchin <guro@fb.com>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Kernel Team <Kernel-team@fb.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Shakeel Butt <shakeelb@google.com>
Subject: Re: [PATCH] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly
Date: Wed, 30 Oct 2019 21:35:19 +0000	[thread overview]
Message-ID: <20191030213513.GA15706@castle.DHCP.thefacebook.com> (raw)
In-Reply-To: <20191030210314.2el7wysojucqypoq@ca-dmjordan1.us.oracle.com>

On Wed, Oct 30, 2019 at 05:03:14PM -0400, Daniel Jordan wrote:
> Hi Roman,
> 
> On Fri, Oct 25, 2019 at 04:27:10PM -0700, Roman Gushchin wrote:
> > page_cgroup_ino() doesn't return a valid memcg pointer for non-compund
> > slab pages, because it depends on PgHead AND PgSlab flags to be set
> > to determine the memory cgroup from the kmem_cache.
> > It's correct for compound pages, but not for generic small pages. Those
> > don't have PgHead set, so it ends up returning zero.
> > 
> > Fix this by replacing the condition to PageSlab() && !PageTail().
> 
> You may also want to update the comment above memcg_from_slab_page():
> 
>  * So this function assumes that the page can pass PageHead() and PageSlab()
>  * checks.

Good catch, thank you! Will send v2 in no time.

      reply	other threads:[~2019-10-30 21:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-25 23:27 [PATCH] mm: slab: make page_cgroup_ino() to recognize non-compound slab pages properly Roman Gushchin
2019-10-30 19:40 ` Roman Gushchin
2019-10-30 20:40 ` Shakeel Butt
2019-10-30 21:03 ` Daniel Jordan
2019-10-30 21:35   ` Roman Gushchin [this message]

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