[PATCH 06/13] selftest/mm: adjust hugepage-mremap test size for large huge pages

[Sayali Patil <sayalip@linux.ibm.com>]

The hugepage-mremap selftest uses a default size of 10MB, which is
sufficient for small huge page sizes. However, when the huge page size
is large (e.g. 1GB), 10MB is smaller than a single huge page.
As a result, the test does not trigger PMD sharing and the
corresponding unshare path in mremap(), causing the
test to fail (mremap succeeds where a failure is expected).

Update run_vmtest.sh to use twice the huge page size when the huge page
size exceeds 10MB, while retaining the 10MB default for smaller huge
pages. This ensures the test exercises the intended PMD sharing and
unsharing paths for larger huge page sizes.

Before patch:
 running ./hugepage-mremap
 ------------------------------
 TAP version 13
 1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fffaa600000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
 Bail out! mremap: Expected failure, but call succeeded
 Planned tests != run tests (1 != 0)
 Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
 [FAIL]
 not ok 1 hugepage-mremap # exit=1

Before patch:
 running ./hugepage-mremap
 ------------------------------
 TAP version 13
 1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fffaa600000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
 Bail out! mremap: Expected failure, but call succeeded
 Planned tests != run tests (1 != 0)
 Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
 [FAIL]
 not ok 1 hugepage-mremap # exit=1

After patch:
 running ./hugepage-mremap 2048
 ------------------------------
 TAP version 13
 1..1
  Map haddr: Returned address is 0x7eaa40000000
  Map daddr: Returned address is 0x7daa40000000
  Map vaddr: Returned address is 0x7faa40000000
  Address returned by mmap() = 0x7fff13000000
  Mremap: Returned address is 0x7faa40000000
  First hex is 0
  First hex is 3020100
  ok 1 Read same data
 Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0
 [PASS]
 ok 1 hugepage-mremap 2048

Fixes: f77a286de48c ("mm, hugepages: make memory size variable in hugepage-mremap selftest")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
---
 tools/testing/selftests/mm/run_vmtests.sh | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh
index afdcfd0d7cef..7273c3e18227 100755
--- a/tools/testing/selftests/mm/run_vmtests.sh
+++ b/tools/testing/selftests/mm/run_vmtests.sh
@@ -293,7 +293,18 @@ echo "$shmmax" > /proc/sys/kernel/shmmax
 echo "$shmall" > /proc/sys/kernel/shmall
 
 CATEGORY="hugetlb" run_test ./map_hugetlb
-CATEGORY="hugetlb" run_test ./hugepage-mremap
+
+# If the huge page size is larger than 10MB, increase the test memory size
+# to twice the huge page size (in MB) to ensure the test exercises PMD sharing
+# and the unshare path in hugepage-mremap. Otherwise, run the test with
+# the default 10MB memory size.
+if [ "$hpgsize_KB" -gt 10240 ]; then
+	len_mb=$(( (2 * hpgsize_KB) / 1024 ))
+	CATEGORY="hugetlb" run_test ./hugepage-mremap "${len_mb}"
+else
+	CATEGORY="hugetlb" run_test ./hugepage-mremap
+fi
+
 CATEGORY="hugetlb" run_test ./hugepage-vmemmap
 CATEGORY="hugetlb" run_test ./hugetlb-madvise
 CATEGORY="hugetlb" run_test ./hugetlb_dio
-- 
2.52.0