selftests/mm: ensure destination is hugetlb-backed in hugetlb-mremap

The hugetlb-mremap selftest reserves the destination address using a
anonymous base-page mapping before calling mremap() with MREMAP_FIXED,
while the source region is hugetlb-backed.

When remapping a hugetlb mapping into a base-page VMA may fail with:

    mremap: Device or resource busy

This is observed on powerpc hash MMU systems where slice constraints and
page size incompatibilities prevent the remap.

Ensure the destination region is created using MAP_HUGETLB so that both
source and destination VMAs are hugetlb-backed and compatible.

Update the FLAGS macro to include MAP_HUGETLB | MAP_SHARED so that both
mappings are hugetlb-backed and compatible.  Also use the macro for the
mmap() calls to avoid repeating the flag combination.

This ensures the test reliably exercises hugetlb mremap instead of failing
due to VMA type mismatch.

Link: https://lore.kernel.org/367644df45c65098f23e3945c6a80f4b8a8964a6.1779296493.git.sayalip@linux.ibm.com
Fixes: 12b613206474 ("mm, hugepages: add hugetlb vma mremap() test")
Signed-off-by: Sayali Patil <sayalip@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
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