selftests/mm: handle EINVAL when configuring gigantic hugepages

Patch series "selftests/mm: avoid false failures in hugetlb and KSM
tests", v3.

This series fixes issues in the hugetlb and KSM MM selftest categories
that can report failures when the prerequisites for the tests are not
satisfied.

Patch 1 updates the hugetlb selftest helpers to handle -EINVAL when
attempting to configure gigantic HugeTLB pages via nr_hugepages.  PowerPC
hash MMU pSeries systems expose gigantic hugepage sizes but do not allow
runtime allocation of such pages, causing the sysfs write to fail.  Handle
this case gracefully and continue running the test instead of aborting.

Patch 2 fixes the KSM NUMA merge test on systems with memoryless NUMA
nodes.  The test currently relies on the number of configured NUMA nodes
and may attempt allocations on nodes that have no memory, resulting in
spurious failures.  Use the existing helpers to identify NUMA nodes that
contain memory and skip the test when fewer than two such nodes are
available.

Patch 3 fixes a pre-existing operator precedence issue in ksm_tests, where
a ternary expression combined with logical OR operators could be evaluated
differently than intended.  Added parentheses to ensure the correct
evaluation order.

These changes improve handling of unsupported test configurations and
unmet test prerequisites, avoiding spurious failures.


This patch (of 3):

Some MM selftests attempt to configure the amount of HugeTLB pages of
different sizes by writing to nr_hugepages.

PowerPC hash MMU pSeries systems advertise gigantic hugepage sizes but do
not support runtime allocation of such pages, writes to the corresponding
nr_hugepages file fail with -EINVAL.  This causes the test to bail out
even though the failure is due to a platform limitation rather than the
functionality being tested.

Ignore -EINVAL when configuring nr_hugepages so that tests continue to run
on systems where gigantic hugepage allocation is unsupported.

Before patch:
   -------------------------
   running ./hugetlb-madvise
   -------------------------
   TAP version 13
   1..1
     [INFO] detected hugetlb page size: 16777216 KiB
     [INFO] detected hugetlb page size: 16384 KiB
    ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb
    Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
    Bail out! /sys/kernel/mm/hugepages/hugepages-16777216kB/nr_hugepages
    write(0) failed: Invalid argument
    Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
    [FAIL]

After patch:
   -------------------------
   running ./hugetlb-madvise
   -------------------------
   TAP version 13
   1..1
    [INFO] detected hugetlb page size: 16777216 KiB
    [INFO] detected hugetlb page size: 16384 KiB
   ok 1 MADV_DONTNEED and MADV_REMOVE on hugetlb
   Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
   [PASS]

Link: https://lore.kernel.org/cover.1783446924.git.sayalip@linux.ibm.com
Link: https://lore.kernel.org/2e3b585cbb30b2fc495dcd49d75de6f6da61861c.1783446924.git.sayalip@linux.ibm.com
Fixes: 27477b28b74f ("selftests/mm: hugepage_settings: add APIs to get and set nr_hugepages")
Co-developed-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions