linux-kernel - Re: [PATCH v4 01/10] ext4: remove writable userspace mappings before truncating page cache

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Message-ID: <b222e406-5f17-47f5-8671-c913452615af@huaweicloud.com>
Date: Tue, 17 Dec 2024 15:38:39 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: Matthew Wilcox <willy@...radead.org>
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 linux-kernel@...r.kernel.org, tytso@....edu, adilger.kernel@...ger.ca,
 jack@...e.cz, yi.zhang@...wei.com, chengzhihao1@...wei.com,
 yukuai3@...wei.com, yangerkun@...wei.com
Subject: Re: [PATCH v4 01/10] ext4: remove writable userspace mappings before
 truncating page cache

On 2024/12/16 23:15, Matthew Wilcox wrote:
> On Mon, Dec 16, 2024 at 09:39:06AM +0800, Zhang Yi wrote:
>>  $mkfs.ext4 -b 1024 /dev/vdb
>>  $mount /dev/vdb /mnt
>>  $xfs_io -t -f -c "pwrite -S 0x58 0 4096" -c "mmap -rw 0 4096" \
>>                -c "mwrite -S 0x5a 2048 2048" -c "fzero 2048 2048" \
>>                -c "mwrite -S 0x59 2048 2048" -c "close" /mnt/foo
>>
>>  $od -Ax -t x1z /mnt/foo
>>  000000 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58
>>  *
>>  000800 59 59 59 59 59 59 59 59 59 59 59 59 59 59 59 59
>>  *
>>  001000
>>
>>  $umount /mnt && mount /dev/vdb /mnt
>>  $od -Ax -t x1z /mnt/foo
>>  000000 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58 58
>>  *
>>  000800 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>  *
>>  001000
> 
> Can you add this to fstests please so we can be sure other filesystems
> don't have the same problem?

Sure, I captured this issue by generic/567 while refactoring punch
hole operation on ext4. The generic/567 only performs a partial punch
hole test but does not include a partial zero range test, so we
did not capture this issue. I will expand this test and add this case.

Thanks,
Yi.