linux-kernel - [PATCH AUTOSEL 6.12 18/30] selftests/mincore: Allow read-ahead pages to reach the end of the file

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Message-Id: <20250414132848.679855-18-sashal@kernel.org>
Date: Mon, 14 Apr 2025 09:28:35 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Qiuxu Zhuo <qiuxu.zhuo@...el.com>,
	Yi Lai <yi1.lai@...el.com>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Sasha Levin <sashal@...nel.org>,
	shuah@...nel.org,
	linux-kselftest@...r.kernel.org
Subject: [PATCH AUTOSEL 6.12 18/30] selftests/mincore: Allow read-ahead pages to reach the end of the file

From: Qiuxu Zhuo <qiuxu.zhuo@...el.com>

[ Upstream commit 197c1eaa7ba633a482ed7588eea6fd4aa57e08d4 ]

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.

Link: https://lore.kernel.org/r/20250311080940.21413-1-qiuxu.zhuo@intel.com
Reported-by: Yi Lai <yi1.lai@...el.com>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@...el.com>
Signed-off-by: Shuah Khan <skhan@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 e949a43a61450..efabfcbe0b498 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.
-- 
2.39.5