From: Hugh Dickins <hughd@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Weijie Yang <weijie.yang@samsung.com>,
hughd@google.com, Minchan Kim <minchan@kernel.org>,
shli@kernel.org, Bob Liu <bob.liu@oracle.com>,
weijie.yang.kh@gmail.com,
Seth Jennings <sjennings@variantweb.net>,
Heesub Shin <heesub.shin@samsung.com>,
mquzik@redhat.com, Linux-MM <linux-mm@kvack.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
stable@vger.kernel.org
Subject: Re: [PATCH 2/8] mm/swap: fix race on swap_info reuse between swapoff and swapon
Date: Mon, 3 Feb 2014 20:14:01 -0800 (PST) [thread overview]
Message-ID: <alpine.LSU.2.11.1402032010180.29889@eggly.anvils> (raw)
In-Reply-To: <20140203152925.89360139306d143f5360fa07@linux-foundation.org>
On Mon, 3 Feb 2014, Andrew Morton wrote:
> On Mon, 3 Feb 2014 15:23:40 -0800 Andrew Morton <akpm@linux-foundation.org> wrote:
> > On Mon, 27 Jan 2014 18:03:04 +0800 Weijie Yang <weijie.yang@samsung.com> wrote:
> >
> > > swapoff clear swap_info's SWP_USED flag prematurely and free its resources
> > > after that. A concurrent swapon will reuse this swap_info while its previous
> > > resources are not cleared completely.
> > >
> > > These late freed resources are:
> > > - p->percpu_cluster
> > > - swap_cgroup_ctrl[type]
> > > - block_device setting
> > > - inode->i_flags &= ~S_SWAPFILE
> > >
> > > This patch clear SWP_USED flag after all its resources freed, so that swapon
> > > can reuse this swap_info by alloc_swap_info() safely.
> > >
> > > This patch is just for a rare scenario, aim to correct of code.
> >
> > I believe that
> > http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch
> > makes this patch redundant?
> >
>
> oop, hang on. This patch *is* a stealth-updated version of
> http://ozlabs.org/~akpm/mmots/broken-out/mm-swap-fix-race-on-swap_info-reuse-between-swapoff-and-swapon.patch.
>
> Undocumented removals of si->swap_map have been added. What's going on
> there?
>
> I think I'll stick with the original patch for now. If you see
> additional optimisations or changes, let's address that separately?
Correct decision, thanks: I explained in an answer when Acking the
previous version why I dislike this version (it would prevent you
from watching the slow progress of swapoff).
Hugh
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prev parent reply other threads:[~2014-02-04 4:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-27 10:03 Weijie Yang
2014-02-03 23:23 ` Andrew Morton
2014-02-03 23:29 ` Andrew Morton
2014-02-04 4:14 ` Hugh Dickins [this message]
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