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

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Message-ID: <b5dd6494-b636-4742-8d96-d8b888d6b9c8@linux.alibaba.com>
Date: Sun, 30 Mar 2025 20:47:48 +0100
From: Baolin Wang <baolin.wang@...ux.alibaba.com>
To: Zi Yan <ziy@...dia.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 2025/3/27 22:36, Zi Yan wrote:
> 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.

It is just a temp file, so it doesn't 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>

Thanks for reviewing.