From: Zhongkun He <hezhongkun.hzk@bytedance.com>
To: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Yosry Ahmed <yosryahmed@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm <linux-mm@kvack.org>,
wuyun.abel@bytedance.com, zhouchengming@bytedance.com,
Nhat Pham <nphamcs@gmail.com>
Subject: Re: [External] Re: [bug report] mm/zswap :memory corruption after zswap_load().
Date: Fri, 22 Mar 2024 11:04:18 +0800 [thread overview]
Message-ID: <CACSyD1OZChmFeG4kMwUH45kNw=2wYMrBnU40gmX_oiX8dcjXWA@mail.gmail.com> (raw)
In-Reply-To: <d280d59f-8760-4f2e-973e-7fecd9c3710c@linux.dev>
On Thu, Mar 21, 2024 at 5:29 PM Chengming Zhou <chengming.zhou@linux.dev> wrote:
>
> On 2024/3/21 14:36, Zhongkun He wrote:
> > On Thu, Mar 21, 2024 at 1:24 PM Chengming Zhou <chengming.zhou@linux.dev> wrote:
> >>
> >> On 2024/3/21 13:09, Zhongkun He wrote:
> >>> On Thu, Mar 21, 2024 at 12:42 PM Chengming Zhou
> >>> <chengming.zhou@linux.dev> wrote:
> >>>>
> >>>> On 2024/3/21 12:34, Zhongkun He wrote:
> >>>>> Hey folks,
> >>>>>
> >>>>> Recently, I tested the zswap with memory reclaiming in the mainline
> >>>>> (6.8) and found a memory corruption issue related to exclusive loads.
> >>>>
> >>>> Is this fix included? 13ddaf26be32 ("mm/swap: fix race when skipping swapcache")
> >>>> This fix avoids concurrent swapin using the same swap entry.
> >>>>
> >>>
> >>> Yes, This fix avoids concurrent swapin from different cpu, but the
> >>> reported issue occurs
> >>> on the same cpu.
> >>
> >> I think you may misunderstand the race description in this fix changelog,
> >> the CPU0 and CPU1 just mean two concurrent threads, not real two CPUs.
> >>
> >> Could you verify if the problem still exists with this fix?
> >
> > Yes，I'm sure the problem still exists with this patch.
> > There is some debug info, not mainline.
> >
> > bpftrace -e'k:swap_readpage {printf("%lld, %lld,%ld,%ld,%ld\n%s",
> > ((struct page *)arg0)->private,nsecs,tid,pid,cpu,kstack)}' --include
> > linux/mm_types.h
>
> Ok, this problem seems only happen on SWP_SYNCHRONOUS_IO swap backends,
> which now include zram, ramdisk, pmem, nvdimm.
Yes.
>
> It maybe not good to use zswap on these swap backends?
>
> The problem here is the page fault handler tries to skip swapcache to
> swapin the folio (swap entry count == 1), but then it can't install folio
> to pte entry since some changes happened such as concurrent fork of entry.
>
The first page fault returned VM_FAULT_RETRY because
folio_lock_or_retry() failed.
> Maybe we should writeback that folio in this special case.
>
next prev parent reply other threads:[~2024-03-22 3:04 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-21 4:34 [bug report] mm/zswap :memory corruption after zswap_load() Zhongkun He
2024-03-21 4:42 ` Chengming Zhou
2024-03-21 5:09 ` [External] " Zhongkun He
2024-03-21 5:24 ` Chengming Zhou
2024-03-21 6:36 ` Zhongkun He
2024-03-21 9:28 ` Chengming Zhou
2024-03-21 15:25 ` Nhat Pham
2024-03-21 18:32 ` Yosry Ahmed
2024-03-22 3:27 ` Chengming Zhou
2024-03-22 3:16 ` Zhongkun He
2024-03-22 3:04 ` Zhongkun He [this message]
2024-03-22 19:34 ` Yosry Ahmed
2024-03-22 23:04 ` Barry Song
2024-03-22 23:08 ` Yosry Ahmed
2024-03-22 23:18 ` Barry Song
2024-03-22 23:22 ` Yosry Ahmed
2024-03-22 23:32 ` Barry Song
2024-03-22 23:34 ` Yosry Ahmed
2024-03-22 23:38 ` Barry Song
2024-03-22 23:41 ` Yosry Ahmed
2024-03-23 0:34 ` Barry Song
2024-03-23 0:42 ` Yosry Ahmed
2024-03-23 10:48 ` Chris Li
2024-03-23 11:27 ` Chris Li
2024-03-23 12:41 ` Zhongkun He
2024-03-23 1:34 ` Zhongkun He
2024-03-23 1:36 ` Yosry Ahmed
2024-03-23 10:52 ` Chris Li
2024-03-23 10:55 ` Barry Song
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