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: <CY8PR11MB7134D020E20B290625057A4089B52@CY8PR11MB7134.namprd11.prod.outlook.com>
Date: Tue, 8 Apr 2025 02:42:38 +0000
From: "Zhuo, Qiuxu" <qiuxu.zhuo@...el.com>
To: "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>
Subject: RE: [PATCH 1/1] selftests/mincore: Allow read-ahead pages to reach
 the end of the file

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>
> ---
>  tools/testing/selftests/mincore/mincore_selftest.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mincore/mincore_selftest.c
> b/tools/testing/selftests/mincore/mincore_selftest.c
> index e949a43a6145..efabfcbe0b49 100644
> --- a/tools/testing/selftests/mincore/mincore_selftest.c
> +++ b/tools/testing/selftests/mincore/mincore_selftest.c
> @@ -261,9 +261,6 @@ TEST(check_file_mmap)
>  		TH_LOG("No read-ahead pages found in memory");
>  	}
> 
> -	EXPECT_LT(i, vec_size) {
> -		TH_LOG("Read-ahead pages reached the end of the file");
> -	}
>  	/*
>  	 * End of the readahead window. The rest of the pages shouldn't
>  	 * be in memory.