selftests/mm: fix ksm NUMA merge test for systems with memoryless NUMA nodes

The KSM NUMA merge test allocates identical pages on different NUMA nodes
and verifies KSM behavior with merge_across_nodes enabled and disabled.

On systems with memoryless NUMA nodes, for example:
 #numactl  -H
      available: 2 nodes (0,4)
      .....
      node 0 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
      node 0 size: 14825 MB
      node 0 free: 1382 MB
      node 4 cpus:
      node 4 size: 0 MB
      node 4 free: 0 MB

the test may attempt to allocate memory on a node without memory, causing
numa_alloc_onnode() to fail and resulting in a spurious test failure.

The test currently checks numa_num_configured_nodes() to determine whether
sufficient NUMA nodes are available.  However, configured nodes do not
necessarily have memory.

Reuse the existing get_first_mem_node() and get_next_mem_node() helpers to
locate NUMA nodes that actually contain memory, and skip the test when
fewer than two such nodes are available.

Before patch:
       ---------------------------
	running ./ksm_tests -N -m 1
       ---------------------------
        mbind: Invalid argument
        ok 1 KSM NUMA merging
	Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
        [PASS]
       ok 1 ksm_tests -N -m 1
       ---------------------------
        running ./ksm_tests -N -m 0
       ---------------------------
        mbind: Invalid argument
        not ok 1 KSM NUMA merging
	Totals: pass:0 fail:1 xfail:0 xpass:0 skip:0 error:0
        [FAIL]
       not ok 2 ksm_tests -N -m 0 # exit=1

After patch:
       ---------------------------
        running ./ksm_tests -N -m 1
       ---------------------------
        At least 2 NUMA nodes with memory must be available
	ok 1
	SKIP KSM NUMA merging
	Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
        [PASS]
        ok 1 ksm_tests -N -m 1
       ---------------------------
        running ./ksm_tests -N -m 0
       ---------------------------
        At least 2 NUMA nodes with memory must be available
	ok 1
	SKIP KSM NUMA merging
	Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0
        [PASS]
        ok 2 ksm_tests -N -m 0

Link: https://lore.kernel.org/78a3b0e3fb94004c0710872c5bab6f7381b7d63c.1783446924.git.sayalip@linux.ibm.com
Fixes: e3820ab252dd ("selftest/vm: fix ksm selftest to run with different NUMA topologies")
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