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>

diff --git a/tools/testing/selftests/mm/hugetlb-mremap.c b/tools/testing/selftests/mm/hugetlb-mremap.c
index 00b4c2cc95a66d1e6a06704bd6b87baeadc204d9..ed3d92e862d876abc5df883f4ee863bef90ebaba 100644 (file)
--- a/tools/testing/selftests/mm/hugetlb-mremap.c
+++ b/tools/testing/selftests/mm/hugetlb-mremap.c
@@ -32,7 +32,7 @@
 #define MB_TO_BYTES(x) (x * 1024 * 1024)
 
 #define PROTECTION (PROT_READ | PROT_WRITE | PROT_EXEC)
-#define FLAGS (MAP_SHARED | MAP_ANONYMOUS)
+#define FLAGS (MAP_HUGETLB | MAP_SHARED)
 
 static void check_bytes(char *addr)
 {
@@ -132,23 +132,20 @@ int main(int argc, char *argv[])
 
        /* mmap to a PUD aligned address to hopefully trigger pmd sharing. */
        unsigned long suggested_addr = 0x7eaa40000000;
-       void *haddr = mmap((void *)suggested_addr, length, PROTECTION,
-                          MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
+       void *haddr = mmap((void *)suggested_addr, length, PROTECTION, FLAGS, fd, 0);
        ksft_print_msg("Map haddr: Returned address is %p\n", haddr);
        if (haddr == MAP_FAILED)
                ksft_exit_fail_msg("mmap1: %s\n", strerror(errno));
 
        /* mmap again to a dummy address to hopefully trigger pmd sharing. */
        suggested_addr = 0x7daa40000000;
-       void *daddr = mmap((void *)suggested_addr, length, PROTECTION,
-                          MAP_HUGETLB | MAP_SHARED | MAP_POPULATE, fd, 0);
+       void *daddr = mmap((void *)suggested_addr, length, PROTECTION, FLAGS, fd, 0);
        ksft_print_msg("Map daddr: Returned address is %p\n", daddr);
        if (daddr == MAP_FAILED)
                ksft_exit_fail_msg("mmap3: %s\n", strerror(errno));
 
        suggested_addr = 0x7faa40000000;
-       void *vaddr =
-               mmap((void *)suggested_addr, length, PROTECTION, FLAGS, -1, 0);
+       void *vaddr = mmap((void *)suggested_addr, length, PROTECTION, FLAGS, fd, 0);
        ksft_print_msg("Map vaddr: Returned address is %p\n", vaddr);
        if (vaddr == MAP_FAILED)
                ksft_exit_fail_msg("mmap2: %s\n", strerror(errno));