@@ -127,6 +127,57 @@ static void mremap_dontunmap_simple()
"unable to unmap source mapping");
}
+// This test validates that MREMAP_DONTUNMAP on a shared mapping works as expected.
+static void mremap_dontunmap_simple_shmem()
+{
+ unsigned long num_pages = 5;
+
+ int mem_fd = memfd_create("memfd", MFD_CLOEXEC);
+ BUG_ON(mem_fd < 0, "memfd_create");
+
+ BUG_ON(ftruncate(mem_fd, num_pages * page_size) < 0,
+ "ftruncate");
+
+ void *source_mapping =
+ mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
+ MAP_FILE | MAP_SHARED, mem_fd, 0);
+ BUG_ON(source_mapping == MAP_FAILED, "mmap");
+
+ BUG_ON(close(mem_fd) < 0, "close");
+
+ memset(source_mapping, 'a', num_pages * page_size);
+
+ // Try to just move the whole mapping anywhere (not fixed).
+ void *dest_mapping =
+ mremap(source_mapping, num_pages * page_size, num_pages * page_size,
+ MREMAP_DONTUNMAP | MREMAP_MAYMOVE, NULL);
+ if (dest_mapping == MAP_FAILED && errno == EINVAL) {
+ // Old kernel which doesn't support MREMAP_DONTUNMAP on shmem.
+ BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
+ "unable to unmap source mapping");
+ return;
+ }
+
+ BUG_ON(dest_mapping == MAP_FAILED, "mremap");
+
+ // Validate that the pages have been moved, we know they were moved if
+ // the dest_mapping contains a's.
+ BUG_ON(check_region_contains_byte
+ (dest_mapping, num_pages * page_size, 'a') != 0,
+ "pages did not migrate");
+
+ // Because the region is backed by shmem, we will actually see the same
+ // memory at the source location still.
+ BUG_ON(check_region_contains_byte
+ (source_mapping, num_pages * page_size, 'a') != 0,
+ "source should have no ptes");
+
+ BUG_ON(munmap(dest_mapping, num_pages * page_size) == -1,
+ "unable to unmap destination mapping");
+ BUG_ON(munmap(source_mapping, num_pages * page_size) == -1,
+ "unable to unmap source mapping");
+}
+
// This test validates MREMAP_DONTUNMAP will move page tables to a specific
// destination using MREMAP_FIXED, also while validating that the source
// remains intact.
@@ -300,6 +351,7 @@ int main(void)
BUG_ON(page_buffer == MAP_FAILED, "unable to mmap a page.");
mremap_dontunmap_simple();
+ mremap_dontunmap_simple_shmem();
mremap_dontunmap_simple_fixed();
mremap_dontunmap_partial_mapping();
mremap_dontunmap_partial_mapping_overwrite();
This test extends the current mremap tests to validate that the MREMAP_DONTUNMAP operation can be performed on shmem mappings. Signed-off-by: Brian Geffon <bgeffon@google.com> --- tools/testing/selftests/vm/mremap_dontunmap.c | 52 +++++++++++++++++++ 1 file changed, 52 insertions(+)