linux-kernel - Re: [PATCH 1/1] selftests/mincore: Allow read-ahead pages to reach the end of the file

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Message-ID: <f9a861ca-754b-41e7-a6dd-16d77958ab51@linuxfoundation.org>
Date: Tue, 8 Apr 2025 17:11:18 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>, "shuah@...nel.org"
 <shuah@...nel.org>
Cc: "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "Lai, Yi1" <yi1.lai@...el.com>, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH 1/1] selftests/mincore: Allow read-ahead pages to reach
 the end of the file

On 4/7/25 20:42, Zhuo, Qiuxu wrote:
> Hi Shuah Khan,
> 
> Just a gentle ping regarding this patch.
> If you have any questions, please feel free to let me know.
> 
> Thanks!
> -Qiuxu
> 
>> From: Zhuo, Qiuxu <qiuxu.zhuo@...el.com>
>> [...]
>> Subject: [PATCH 1/1] selftests/mincore: Allow read-ahead pages to reach the
>> end of the file
>>
>> When running the mincore_selftest on a system with an XFS file system, it
>> failed the "check_file_mmap" test case due to the read-ahead pages reaching
>> the end of the file. The failure log is as below:
>>
>>     RUN           global.check_file_mmap ...
>>    mincore_selftest.c:264:check_file_mmap:Expected i (1024) < vec_size (1024)
>>    mincore_selftest.c:265:check_file_mmap:Read-ahead pages reached the
>> end of the file
>>    check_file_mmap: Test failed
>>             FAIL  global.check_file_mmap
>>
>> This is because the read-ahead window size of the XFS file system on this
>> machine is 4 MB, which is larger than the size from the #PF address to the end
>> of the file. As a result, all the pages for this file are populated.
>>
>>    blockdev --getra /dev/nvme0n1p5
>>      8192
>>    blockdev --getbsz /dev/nvme0n1p5
>>      512
>>
>> This issue can be fixed by extending the current FILE_SIZE 4MB to a larger
>> number, but it will still fail if the read-ahead window size of the file system is
>> larger enough. Additionally, in the real world, read-ahead pages reaching the
>> end of the file can happen and is an expected behavior.
>> Therefore, allowing read-ahead pages to reach the end of the file is a better
>> choice for the "check_file_mmap" test case.
>>
>> Reported-by: Yi Lai <yi1.lai@...el.com>
>> Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
>> ---

Applied for Linux 6.15-rc2

https://web.git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest.git/log/?h=fixes

thanks,
-- Shuah