linux-kernel - Re: [PATCH v2 1/2] mm, thp: check page mapping when truncating page cache

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Date:   Tue, 5 Oct 2021 09:58:42 +0800
From:   Rongwei Wang <rongwei.wang@...ux.alibaba.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Song Liu <song@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        William Kucharski <william.kucharski@...cle.com>
Subject: Re: [PATCH v2 1/2] mm, thp: check page mapping when truncating page
 cache



On 10/5/21 3:05 AM, Matthew Wilcox wrote:
> On Tue, Oct 05, 2021 at 01:26:50AM +0800, Rongwei Wang wrote:
>> Hi,
>> I have run our cases these two days to stress test new Patch #1. The new
>> Patch #1 mainly add filemap_invalidate_{un}lock before and after
>> truncate_pagecache(), basing on original Patch #1. And the crash has not
>> happened.
> 
> You shouldn't need most of patch 1.
> 
> In fact, the only two patches you should need would be this:
> 
> +++ b/mm/filemap.c
> @@ -2093,7 +2093,6 @@ unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
>                  if (!xa_is_value(page)) {
>                          if (page->index < start)
>                                  goto put;
> -                       VM_BUG_ON_PAGE(page->index != xas.xa_index, page);
>                          if (page->index + thp_nr_pages(page) - 1 > end)
>                                  goto put;
>                          if (!trylock_page(page))
> 
> (already in Andrew's tree) and:
> 
>> -               if (filemap_nr_thps(inode->i_mapping))
>> +               if (filemap_nr_thps(inode->i_mapping)) {
>> +                       filemap_invalidate_lock(inode->i_mapping);
>>                          truncate_pagecache(inode, 0);
>> +                       filemap_invalidate_unlock(inode->i_mapping);
>> +               }
> 
> If you can still hit a bug with just those two patches, then something
> else is going wrong, and needs to be investigated.
OK, I see what your mean. I will send Patch v3 and only keep 
filemap_invalidate_{un}lock in Patch #1.

Thanks!
>