linux-kernel - Re: [PATCH 1/2] selftests: mincore: fix tmpfs mincore test failure

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Message-ID: <992DD536-7047-4C2C-97EB-7F23100143E3@nvidia.com>
Date: Thu, 27 Mar 2025 10:36:42 -0400
From: Zi Yan <ziy@...dia.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc: akpm@...ux-foundation.org, hughd@...gle.com, willy@...radead.org,
 david@...hat.com, 21cnbao@...il.com, ryan.roberts@....com,
 linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] selftests: mincore: fix tmpfs mincore test failure

On 25 Mar 2025, at 23:38, Baolin Wang wrote:

> When running mincore test cases, I encountered the following failures:
>
> "
> mincore_selftest.c:359:check_tmpfs_mmap:Expected ra_pages (511) == 0 (0)
> mincore_selftest.c:360:check_tmpfs_mmap:Read-ahead pages found in memory
> check_tmpfs_mmap: Test terminated by assertion
>           FAIL  global.check_tmpfs_mmap
> not ok 5 global.check_tmpfs_mmap
> FAILED: 4 / 5 tests passed
> "
>
> The reason for the test case failure is that my system automatically enabled
> tmpfs large folio allocation by adding the 'transparent_hugepage_tmpfs=always'
> cmdline. However, the test case still expects the tmpfs mounted on /dev/shm to
> allocate small folios, which leads to assertion failures when verifying readahead
> pages.
>
> To fix this issue, remount tmpfs to a new test directory and set the 'huge=never'
> parameter to avoid allocating large folios, which can pass the test.
>
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> ---
>  .../selftests/mincore/mincore_selftest.c      | 25 +++++++++++++++++--
>  1 file changed, 23 insertions(+), 2 deletions(-)
>

<snip>

>
>  	errno = 0;
> -	fd = open("/dev/shm", O_TMPFILE | O_RDWR, 0600);
> +	/* Do not use large folios for tmpfs mincore testing */
> +	retval = mount("tmpfs", tmpfs_loc, "tmpfs", 0, "huge=never,size=4M");
> +	ASSERT_EQ(0, retval) {
> +		TH_LOG("Unable to mount tmpfs for testing\n");
> +	}
> +
> +	retval = snprintf(testfile, INPUT_MAX, "%s/test_file", tmpfs_loc);
> +	ASSERT_GE(INPUT_MAX, retval) {
> +		TH_LOG("Unable to create a tmpfs for testing\n");
> +	}
> +
> +	fd = open(testfile, O_CREAT|O_RDWR, 0664);

The fd permission is changed from 0600 to 0664, but it probably does not
matter.

>  	ASSERT_NE(-1, fd) {
>  		TH_LOG("Can't create temporary file: %s",
>  			strerror(errno));
> @@ -363,6 +382,8 @@ TEST(check_tmpfs_mmap)
>  	munmap(addr, FILE_SIZE);
>  	close(fd);
>  	free(vec);
> +	umount(tmpfs_loc);
> +	rmdir(tmpfs_loc);
>  }
>
>  TEST_HARNESS_MAIN
> -- 
> 2.43.5

Otherwise, LGTM. Reviewed-by: Zi Yan <ziy@...dia.com>

--
Best Regards,
Yan, Zi