From: Johannes Weiner <hannes@cmpxchg.org>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@suse.cz>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH mmotm/next] mm: memcontrol: rewrite charge API: fix shmem_unuse
Date: Wed, 2 Jul 2014 18:37:50 -0400 [thread overview]
Message-ID: <20140702223750.GA910@cmpxchg.org> (raw)
In-Reply-To: <alpine.LSU.2.11.1406301541420.4349@eggly.anvils>
On Mon, Jun 30, 2014 at 03:48:39PM -0700, Hugh Dickins wrote:
> Under shmem swapping and swapoff load, I sometimes hit the
> VM_BUG_ON_PAGE(!page->mapping) in mem_cgroup_commit_charge() at
> mm/memcontrol.c:6502! Each time it has been a call from shmem_unuse().
>
> Yes, there are some cases (most commonly when the page being unswapped
> is in a file being unlinked and evicted at that time) when the charge
> should not be committed. In the old scheme, the page got uncharged
> again on release; but in the new scheme, it hits that BUG beforehand.
>
> It's a useful BUG, so adapt shmem_unuse() to allow for it. Which needs
> more info from shmem_unuse_inode(): so abuse -EAGAIN internally to
> replace the previous !found state (-ENOENT would be a more natural
> code, but that's exactly what you get when the swap has been evicted).
>
> Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Thanks, Hugh!
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prev parent reply other threads:[~2014-07-02 22:37 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-30 22:48 [PATCH mmotm/next] mm: memcontrol: rewrite charge API: fix shmem_unuse Hugh Dickins
2014-06-30 23:02 ` Andrew Morton
2014-07-01 0:10 ` Hugh Dickins
2014-07-01 0:34 ` Andrew Morton
2014-07-01 1:06 ` Hugh Dickins
2014-07-02 22:37 ` Johannes Weiner [this message]
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