From: Hugh Dickins <hughd@google.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>, Michal Hocko <mhocko@kernel.org>,
Naresh Kamboju <naresh.kamboju@linaro.org>,
Chris Down <chris@chrisdown.name>,
Yafang Shao <laoar.shao@gmail.com>,
Anders Roxell <anders.roxell@linaro.org>,
"Linux F2FS DEV,
Mailing List" <linux-f2fs-devel@lists.sourceforge.net>,
linux-ext4 <linux-ext4@vger.kernel.org>,
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open list <linux-kernel@vger.kernel.org>,
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Andreas Dilger <adilger.kernel@dilger.ca>,
Jaegeuk Kim <jaegeuk@kernel.org>, Theodore Ts'o <tytso@mit.edu>,
Chao Yu <chao@kernel.org>, Andrea Arcangeli <aarcange@redhat.com>,
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Subject: Re: mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page
Date: Thu, 21 May 2020 16:35:42 -0700 (PDT) [thread overview]
Message-ID: <alpine.LSU.2.11.2005211614320.1102@eggly.anvils> (raw)
In-Reply-To: <20200521215855.GB815153@cmpxchg.org>
On Thu, 21 May 2020, Johannes Weiner wrote:
> On Thu, May 21, 2020 at 01:06:28PM -0700, Hugh Dickins wrote:
> > On Thu, 21 May 2020, Johannes Weiner wrote:
> > > do_memsw_account() used to be automatically false when the cgroup
> > > controller was disabled. Now that it's replaced by
> > > cgroup_memory_noswap, for which this isn't true, make the
> > > mem_cgroup_disabled() checks explicit in the swap control API.
> > >
> > > [hannes@cmpxchg.org: use mem_cgroup_disabled() in all API functions]
> > > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> > > Debugged-by: Hugh Dickins <hughd@google.com>
> > > Debugged-by: Michal Hocko <mhocko@kernel.org>
> > > Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> > > ---
> > > mm/memcontrol.c | 47 +++++++++++++++++++++++++++++++++++++++++------
> > > 1 file changed, 41 insertions(+), 6 deletions(-)
> >
> > I'm certainly not against a mem_cgroup_disabled() check in the only
> > place that's been observed to need it, as a fixup to merge into your
> > original patch; but this seems rather an over-reaction - and I'm a
> > little surprised that setting mem_cgroup_disabled() doesn't just
> > force cgroup_memory_noswap, saving repetitious checks elsewhere
> > (perhaps there's a difficulty in that, I haven't looked).
>
> Fair enough, I changed it to set the flag at initialization time if
> mem_cgroup_disabled(). I was never a fan of the old flags, where it
> was never clear what was commandline, and what was internal runtime
> state - do_swap_account? really_do_swap_account? But I think it's
> straight-forward in this case now.
>
> > Historically, I think we've added mem_cgroup_disabled() checks
> > (accessing a cacheline we'd rather avoid) where they're necessary,
> > rather than at every "interface".
>
> To me that always seemed like bugs waiting to happen. Like this one!
>
> It's a jump label nowadays, so I've been liberal with these to avoid
> subtle bugs.
>
> > And you seem to be in a very "goto out" mood today - we all have
> > our "goto out" days, alternating with our "return 0" days :)
>
> :-)
>
> But I agree, best to keep this fixup self-contained and defer anything
> else to separate cleanup patches.
>
> How about the below? It survives a swaptest with cgroup_disable=memory
> for me.
I like this version *a lot*, thank you. I got worried for a bit by
the "#define cgroup_memory_noswap 1" when #ifndef CONFIG_MEMCG_SWAP,
but now realize that fits perfectly.
>
> Hugh, I started with your patch, which is why I kept you as the
> author, but as the patch now (and arguably the previous one) is
> sufficiently different, I dropped that now. I hope that's okay.
Absolutely okay, these are yours: I was a little uncomfortable to
see me on the From line before, but it also seemed just too petty
to insist that my name be removed.
(By the way, off-topic for this particular issue, but advance warning
that I hope to post a couple of patches to __read_swap_cache_async()
before the end of the day, first being fixup to some of your mods -
I suspect you got it working well enough, and intended to come back
to check a few details later, but never quite got around to that.)
>
> ---
> From d9e7ed15d1c9248a3fd99e35e82437549154dac7 Mon Sep 17 00:00:00 2001
> From: Johannes Weiner <hannes@cmpxchg.org>
> Date: Thu, 21 May 2020 17:44:25 -0400
> Subject: [PATCH] mm: memcontrol: prepare swap controller setup for integration
> fix
>
> Fix crash with cgroup_disable=memory:
>
> > > > > + mkfs -t ext4 /dev/disk/by-id/ata-TOSHIBA_MG04ACA100N_Y8NRK0BPF6XF
> > > > > mke2fs 1.43.8 (1-Jan-2018)
> > > > > Creating filesystem with 244190646 4k blocks and 61054976 inodes
> > > > > Filesystem UUID: 3bb1a285-2cb4-44b4-b6e8-62548f3ac620
> > > > > Superblock backups stored on blocks:
> > > > > 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
> > > > > 4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
> > > > > 102400000, 214990848
> > > > > Allocating group tables: 0/7453 done
> > > > > Writing inode tables: 0/7453 done
> > > > > Creating journal (262144 blocks): [ 35.502102] BUG: kernel NULL
> > > > > pointer dereference, address: 000000c8
> > > > > [ 35.508372] #PF: supervisor read access in kernel mode
> > > > > [ 35.513506] #PF: error_code(0x0000) - not-present page
> > > > > [ 35.518638] *pde = 00000000
> > > > > [ 35.521514] Oops: 0000 [#1] SMP
> > > > > [ 35.524652] CPU: 0 PID: 145 Comm: kswapd0 Not tainted
> > > > > 5.7.0-rc6-next-20200519+ #1
> > > > > [ 35.532121] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS
> > > > > 2.2 05/23/2018
> > > > > [ 35.539507] EIP: mem_cgroup_get_nr_swap_pages+0x28/0x60
>
> Swap accounting used to be implied-disabled when the cgroup controller
> was disabled. Restore that for the new cgroup_memory_noswap, so that
> we bail out of this function instead of dereferencing a NULL memcg.
>
> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
> Debugged-by: Hugh Dickins <hughd@google.com>
> Debugged-by: Michal Hocko <mhocko@kernel.org>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Hugh Dickins <hughd@google.com>
> ---
> mm/memcontrol.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 3e000a316b59..e3b785d6e771 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -7075,7 +7075,11 @@ static struct cftype memsw_files[] = {
>
> static int __init mem_cgroup_swap_init(void)
> {
> - if (mem_cgroup_disabled() || cgroup_memory_noswap)
> + /* No memory control -> no swap control */
> + if (mem_cgroup_disabled())
> + cgroup_memory_noswap = true;
> +
> + if (cgroup_memory_noswap)
> return 0;
>
> WARN_ON(cgroup_add_dfl_cftypes(&memory_cgrp_subsys, swap_files));
> --
> 2.26.2
next prev parent reply other threads:[~2020-05-21 23:36 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-01 12:38 mm: mkfs.ext4 invoked oom-killer on i386 - pagecache_get_page Naresh Kamboju
2020-05-01 20:58 ` Andrew Morton
2020-05-18 14:10 ` Naresh Kamboju
2020-05-19 7:52 ` Michal Hocko
2020-05-19 8:11 ` Arnd Bergmann
2020-05-19 8:45 ` Michal Hocko
2020-05-20 11:56 ` Naresh Kamboju
2020-05-20 17:59 ` Naresh Kamboju
2020-05-20 19:09 ` Chris Down
2020-05-21 9:22 ` Naresh Kamboju
2020-05-21 9:35 ` Arnd Bergmann
2020-05-21 9:55 ` Michal Hocko
2020-05-21 10:41 ` Naresh Kamboju
2020-05-21 10:58 ` Michal Hocko
2020-05-21 12:24 ` Hugh Dickins
2020-05-21 12:44 ` Michal Hocko
2020-05-21 19:17 ` Johannes Weiner
2020-05-21 20:06 ` Hugh Dickins
2020-05-21 21:58 ` Johannes Weiner
2020-05-21 23:35 ` Hugh Dickins [this message]
2020-05-28 14:59 ` Michal Hocko
2020-05-21 16:34 ` Michal Hocko
2020-05-21 19:00 ` Naresh Kamboju
2020-05-21 20:53 ` Naresh Kamboju
2020-05-28 15:03 ` Michal Hocko
2020-05-28 16:17 ` Naresh Kamboju
2020-05-28 16:41 ` Chris Down
2020-05-29 1:50 ` Yafang Shao
2020-05-29 1:56 ` Chris Down
2020-05-29 9:49 ` Michal Hocko
2020-06-11 9:55 ` Michal Hocko
2020-06-12 9:43 ` Naresh Kamboju
2020-06-12 12:09 ` Michal Hocko
2020-06-17 13:37 ` Naresh Kamboju
2020-06-17 13:57 ` Chris Down
2020-06-17 14:11 ` Michal Hocko
2020-06-17 15:53 ` Naresh Kamboju
2020-06-17 16:06 ` Michal Hocko
2020-06-17 20:13 ` Naresh Kamboju
2020-06-17 21:09 ` Chris Down
2020-06-18 1:43 ` Yafang Shao
2020-06-18 12:37 ` Chris Down
2020-06-18 12:41 ` Michal Hocko
2020-06-18 12:49 ` Chris Down
2020-06-18 14:59 ` Yafang Shao
2020-06-17 13:59 ` Michal Hocko
2020-06-17 14:08 ` Chris Down
2020-05-21 2:39 ` Yafang Shao
2020-05-21 8:58 ` Naresh Kamboju
2020-05-21 9:47 ` Yafang Shao
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