From: Andrew Morton <akpm@linux-foundation.org>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: "HORIGUCHI NAOYA" <naoya.horiguchi@nec.com>,
"hughd@google.com" <hughd@google.com>,
"willy@infradead.org" <willy@infradead.org>,
"vbabka@suse.cz" <vbabka@suse.cz>,
"dhowells@redhat.com" <dhowells@redhat.com>,
"neilb@suse.de" <neilb@suse.de>,
"apopple@nvidia.com" <apopple@nvidia.com>,
"david@redhat.com" <david@redhat.com>,
"surenb@google.com" <surenb@google.com>,
"peterx@redhat.com" <peterx@redhat.com>,
"rcampbell@nvidia.com" <rcampbell@nvidia.com>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 4/5] mm/shmem: fix infinite loop when swap in shmem error at swapoff time
Date: Tue, 24 May 2022 15:10:14 -0700 [thread overview]
Message-ID: <20220524151014.4d16f01cbd1c04ef74e4db5e@linux-foundation.org> (raw)
In-Reply-To: <0f6dc98b-88f4-c0c9-eb7b-5356ad0e08b1@huawei.com>
On Sat, 21 May 2022 17:34:28 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
> On 2022/5/20 14:34, HORIGUCHI NAOYA(堀口 直也) wrote:
> > On Thu, May 19, 2022 at 08:50:29PM +0800, Miaohe Lin wrote:
> >> When swap in shmem error at swapoff time, there would be a infinite loop
> >> in the while loop in shmem_unuse_inode(). It's because swapin error is
> >> deliberately ignored now and thus info->swapped will never reach 0. So
> >> we can't escape the loop in shmem_unuse().
> >>
> >> In order to fix the issue, swapin_error entry is stored in the mapping
> >> when swapin error occurs. So the swapcache page can be freed and the
> >> user won't end up with a permanently mounted swap because a sector is
> >> bad. If the page is accessed later, the user process will be killed
> >> so that corrupted data is never consumed. On the other hand, if the
> >> page is never accessed, the user won't even notice it.
> >>
> >> Reported-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
> >> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> >
> > Hi Miaohe,
> >
> > Thank you for the update. I might miss something, but I still see the same
> > problem (I checked it on mm-everything-2022-05-19-00-03 + this patchset).
>
> Hi Naoya,
> I reproduce the issue in the linux-next-next-20220520 version. And I found even if
> I *do not inject the swapin error*, the deadloop still occurs. After investigating the
> code for a long while, I found the root cause:
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index d55dd972023a..6d23ed4d23cb 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1182,7 +1182,7 @@ static int shmem_find_swap_entries(struct address_space *mapping,
> if (swp_type(entry) != type)
> continue;
>
> - indices[ret] = xas.xa_index;
> + indices[ret++] = xas.xa_index;
> if (!folio_batch_add(fbatch, folio))
> break;
>
> The origin code does not increment the ret value when a folio is found. I will send a patch
> to fix this next week. Thanks! :)
So I'm thinking that with Hugh's "mm/shmem: fix shmem folio swapoff
hang", this patchset is now looking OK, so
mm-swapfile-unuse_pte-can-map-random-data-if-swap-read-fails.patch
mm-swapfile-fix-lost-swap-bits-in-unuse_pte.patch
mm-madvise-free-hwpoison-and-swapin-error-entry-in-madvise_free_pte_range.patch
mm-shmem-fix-infinite-loop-when-swap-in-shmem-error-at-swapoff-time.patch
mm-filter-out-swapin-error-entry-in-shmem-mapping.patch
#
are OK for merging into mainline?
next prev parent reply other threads:[~2022-05-24 22:10 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-19 12:50 [PATCH v4 0/5] A few fixup patches for mm Miaohe Lin
2022-05-19 12:50 ` [PATCH v4 1/5] mm/swapfile: unuse_pte can map random data if swap read fails Miaohe Lin
2022-05-19 12:50 ` [PATCH v4 2/5] mm/swapfile: Fix lost swap bits in unuse_pte() Miaohe Lin
2022-05-19 12:50 ` [PATCH v4 3/5] mm/madvise: free hwpoison and swapin error entry in madvise_free_pte_range Miaohe Lin
2022-05-19 12:50 ` [PATCH v4 4/5] mm/shmem: fix infinite loop when swap in shmem error at swapoff time Miaohe Lin
2022-05-20 6:34 ` HORIGUCHI NAOYA(堀口 直也)
2022-05-20 8:17 ` Miaohe Lin
2022-05-22 23:53 ` HORIGUCHI NAOYA(堀口 直也)
2022-05-23 3:01 ` Miaohe Lin
2022-05-23 11:23 ` Miaohe Lin
2022-05-24 6:44 ` HORIGUCHI NAOYA(堀口 直也)
2022-05-24 10:56 ` Miaohe Lin
2022-05-21 9:34 ` Miaohe Lin
2022-05-24 22:10 ` Andrew Morton [this message]
2022-05-25 1:42 ` Miaohe Lin
2022-05-25 4:32 ` HORIGUCHI NAOYA(堀口 直也)
2022-05-25 6:40 ` Miaohe Lin
2022-05-26 6:08 ` HORIGUCHI NAOYA(堀口 直也)
2022-05-19 12:50 ` [PATCH v4 5/5] mm: filter out swapin error entry in shmem mapping Miaohe Lin
2022-05-25 4:53 ` HORIGUCHI NAOYA(堀口 直也)
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