From: Miaohe Lin <linmiaohe@huawei.com>
To: "HORIGUCHI NAOYA(堀口 直也)" <naoya.horiguchi@nec.com>
Cc: "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
"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: Wed, 25 May 2022 14:40:40 +0800 [thread overview]
Message-ID: <dd9ac56b-c50a-6c6f-339b-50c347f601b4@huawei.com> (raw)
In-Reply-To: <20220525043233.GA808704@hori.linux.bs1.fc.nec.co.jp>
On 2022/5/25 12:32, 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>
>> ---
>
> ...
>> @@ -1672,6 +1676,36 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
>> return error;
>> }
>>
>> +static void shmem_set_folio_swapin_error(struct inode *inode, pgoff_t index,
>> + struct folio *folio, swp_entry_t swap)
>> +{
>> + struct address_space *mapping = inode->i_mapping;
>> + struct shmem_inode_info *info = SHMEM_I(inode);
>> + swp_entry_t swapin_error;
>> + void *old;
>> +
>> + swapin_error = make_swapin_error_entry(&folio->page);
>> + old = xa_cmpxchg_irq(&mapping->i_pages, index,
>> + swp_to_radix_entry(swap),
>> + swp_to_radix_entry(swapin_error), 0);
>> + if (old != swp_to_radix_entry(swap))
>> + return;
>> +
>> + folio_wait_writeback(folio);
>> + delete_from_swap_cache(&folio->page);
>> + spin_lock_irq(&info->lock);
>> + /*
>> + * Don't treat swapin error folio as alloced. Otherwise inode->i_blocks won't
>> + * be 0 when inode is released and thus trigger WARN_ON(inode->i_blocks) in
>> + * shmem_evict_inode.
>> + */
>> + info->alloced--;
>> + info->swapped--;
>
> I'm not familiar with folio yet and might miss some basic thing,
> but is it OK to decrement by one instead of folio_nr_pages()?
info->swapped is also decremented by one in shmem_swapin_folio(). In fact, no huge page
swapin is supported yet (this is also true for non-shmem case). So I think info->swapped--
should be OK. Or am I miss something?
>
> Thanks,
> Naoya Horiguchi
Many thanks for review and comment! It's really helpful! :)
>
next prev parent reply other threads:[~2022-05-25 6:40 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
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 [this message]
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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