The patch titled
Subject: selftest: Add MREMAP_DONTUNMAP selftest.
has been added to the -mm tree. Its filename is
selftest-add-mremap_dontunmap-selftest-v7.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/selftest-add-mremap_dontunmap-selftest-v7.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/selftest-add-mremap_dontunmap-selftest-v7.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Brian Geffon <bgeffon@xxxxxxxxxx>
Subject: selftest: Add MREMAP_DONTUNMAP selftest.
Add a few simple self tests for the new flag MREMAP_DONTUNMAP,
they are simple smoke tests which also demonstrate the behavior.
Link: http://lkml.kernel.org/r/20200221174248.244748-2-bgeffon@xxxxxxxxxx
Signed-off-by: Brian Geffon <bgeffon@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/vm/mremap_dontunmap.c | 91 ++++++----------
1 file changed, 39 insertions(+), 52 deletions(-)
--- a/tools/testing/selftests/vm/mremap_dontunmap.c~selftest-add-mremap_dontunmap-selftest-v7
+++ a/tools/testing/selftests/vm/mremap_dontunmap.c
@@ -36,7 +36,7 @@ static void dump_maps(void)
if (condition) { \
fprintf(stderr, "[FAIL]\t%s():%d\t%s:%s\n", __func__, \
__LINE__, (description), strerror(errno)); \
- dump_maps(); \
+ dump_maps(); \
exit(1); \
} \
} while (0)
@@ -224,73 +224,60 @@ static void mremap_dontunmap_partial_map
"unable to unmap source mapping");
}
-// This test validates that we can shrink an existing mapping via the normal
-// mremap behavior along with the MREMAP_DONTUNMAP flag.
-static void mremap_dontunmap_shrink_mapping()
+// This test validates that we can remap over only a portion of a mapping.
+static void mremap_dontunmap_partial_mapping_overwrite()
{
/*
- * We shrink the source by 5 pages while remapping.
* source mapping:
- * --------------
- * | aaaaaaaaaa |
- * --------------
- * to become:
* ---------
- * | 00000 |
+ * |aaaaa|
* ---------
- * With the destination mapping containing 5 pages of As followed by
- * the original pages of Xs.
- * --------------
- * | aaaaaXXXXX |
- * --------------
+ * dest mapping initially:
+ * -----------
+ * |XXXXXXXXXX|
+ * ------------
+ * Source to become:
+ * ---------
+ * |00000|
+ * ---------
+ * With the destination mapping containing 5 pages of As.
+ * ------------
+ * |aaaaaXXXXX|
+ * ------------
*/
+ void *source_mapping =
+ mmap(NULL, 5 * page_size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ BUG_ON(source_mapping == MAP_FAILED, "mmap");
+ memset(source_mapping, 'a', 5 * page_size);
- unsigned long num_pages = 10;
-
- // We use MREMAP_FIXED because we don't want the mremap to place the
- // remapped mapping behind the source, if it did
- // we wouldn't be able to validate that the mapping was in fact
- // adjusted.
void *dest_mapping =
- mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
+ mmap(NULL, 10 * page_size, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
BUG_ON(dest_mapping == MAP_FAILED, "mmap");
- memset(dest_mapping, 'X', num_pages * page_size);
+ memset(dest_mapping, 'X', 10 * page_size);
- void *source_mapping =
- mmap(NULL, num_pages * page_size, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- BUG_ON(source_mapping == MAP_FAILED, "mmap");
- memset(source_mapping, 'a', num_pages * page_size);
-
- // We are shrinking the mapping while also using MREMAP_DONTUNMAP
+ // We will grab the last 5 pages of the source and move them.
void *remapped_mapping =
- mremap(source_mapping, num_pages * page_size, 5 * page_size,
- MREMAP_FIXED | MREMAP_DONTUNMAP | MREMAP_MAYMOVE,
- dest_mapping);
- BUG_ON(remapped_mapping == MAP_FAILED, "mremap");
- BUG_ON(remapped_mapping != dest_mapping,
- "expected mremap to place mapping at dest");
-
- // The last 5 pages of source should have become unmapped while the
- // first 5 remain.
- unsigned char buf[5];
- int ret = mincore(source_mapping + (5 * page_size), 5 * page_size, buf);
- BUG_ON((ret != -1 || (ret == -1 && errno != ENOMEM)),
- "we expect -ENOMEM from mincore.");
+ mremap(source_mapping, 5 * page_size,
+ 5 * page_size,
+ MREMAP_DONTUNMAP | MREMAP_MAYMOVE | MREMAP_FIXED, dest_mapping);
+ BUG_ON(dest_mapping == MAP_FAILED, "mremap");
+ BUG_ON(dest_mapping != remapped_mapping, "expected to remap to dest_mapping");
BUG_ON(check_region_contains_byte(source_mapping, 5 * page_size, 0) !=
- 0, "source should have no ptes");
- BUG_ON(check_region_contains_byte(dest_mapping, 5 * page_size, 'a') !=
- 0, "dest mapping should contain ptes from the source");
+ 0, "first 5 pages of source should have no ptes");
+
+ // Finally we expect the destination to have 5 pages worth of a's.
+ BUG_ON(check_region_contains_byte(dest_mapping, 5 * page_size, 'a') != 0,
+ "dest mapping should contain ptes from the source");
- // And the second half of the destination should be unchanged.
+ // Finally the last 5 pages shouldn't have been touched.
BUG_ON(check_region_contains_byte(dest_mapping + (5 * page_size),
- 5 * page_size, 'X') != 0,
- "second half of dest shouldn't be touched");
+ 5 * page_size, 'X') != 0,
+ "dest mapping should have retained the last 5 pages");
- // Cleanup
- BUG_ON(munmap(dest_mapping, num_pages * page_size) == -1,
+ BUG_ON(munmap(dest_mapping, 10 * page_size) == -1,
"unable to unmap destination mapping");
BUG_ON(munmap(source_mapping, 5 * page_size) == -1,
"unable to unmap source mapping");
@@ -316,7 +303,7 @@ int main(void)
mremap_dontunmap_simple();
mremap_dontunmap_simple_fixed();
mremap_dontunmap_partial_mapping();
- mremap_dontunmap_shrink_mapping();
+ mremap_dontunmap_partial_mapping_overwrite();
BUG_ON(munmap(page_buffer, page_size) == -1,
"unable to unmap page buffer");
_
Patches currently in -mm which might be from bgeffon@xxxxxxxxxx are
mm-add-mremap_dontunmap-to-mremap.patch
mm-add-mremap_dontunmap-to-mremap-v6.patch
mm-add-mremap_dontunmap-to-mremap-v7.patch
selftest-add-mremap_dontunmap-selftest.patch
selftest-add-mremap_dontunmap-selftest-v7.patch
