Yijia Wang 51f4bd13c3 selftests: mincore: count file-mmap readahead on both sides ...

check_file_mmap() faults a page in the middle of a file mapping and
expects the mmap read-around path to make neighbouring pages resident. 
The test currently counts only pages after the faulted page.

That misses valid read-around on systems with large base page sizes.  On
arm64 with 64K pages and the default 128K readahead setting, the
read-around window is two pages wide and centred on the faulting page. 
Faulting page 32 makes pages 31 and 32 resident, so the forward-only scan
from page 33 reports ra_pages == 0 even though a neighbouring page was
brought in.

Keep the existing readahead assertion, but count resident neighbouring
pages on both sides of the faulted page.  This fixes the 64K-page false
failure without teaching the selftest to compute the expected readahead
window from sysfs or other implementation details.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Yijia Wang <[email protected]>
Cc: "Matthew Wilcox (Oracle)" <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Shuah Khan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

2026-08-06 18:56:55 -07:00

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.gitignore

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Makefile

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mincore_selftest.c

selftests: mincore: count file-mmap readahead on both sides

2026-08-06 18:56:55 -07:00