The patch titled
Subject: selftests: mm: add a test for remapping to area immediately after existing mapping
has been added to the -mm mm-unstable branch. Its filename is
selftests-mm-add-a-test-for-remapping-to-area-immediately-after-existing-mapping.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-add-a-test-for-remapping-to-area-immediately-after-existing-mapping.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Joel Fernandes (Google)" <joel@xxxxxxxxxxxxxxxxx>
Subject: selftests: mm: add a test for remapping to area immediately after existing mapping
Date: Sun, 3 Sep 2023 15:13:26 +0000
This patch adds support for verifying that we correctly handle the
situation where something is already mapped before the destination of the remap.
Any realignment of destination address and PMD-copy will destroy that
existing mapping. In such cases, we need to avoid doing the optimization.
To test this, we map an area called the preamble before the remap
region. Then we verify after the mremap operation that this region did not get
corrupted.
Putting some prints in the kernel, I verified that we optimize
correctly in different situations:
Optimize when there is alignment and no previous mapping (this is tested
by previous patch).
<prints>
can_align_down(old_vma->vm_start=2900000, old_addr=2900000, mask=-2097152): 0
can_align_down(new_vma->vm_start=2f00000, new_addr=2f00000, mask=-2097152): 0
=== Starting move_page_tables ===
Doing PUD move for 2800000 -> 2e00000 of extent=200000 <-- Optimization
Doing PUD move for 2a00000 -> 3000000 of extent=200000
Doing PUD move for 2c00000 -> 3200000 of extent=200000
</prints>
Don't optimize when there is alignment but there is previous mapping
(this is tested by this patch).
Notice that can_align_down() returns 1 for the destination mapping
as we detected there is something there.
<prints>
can_align_down(old_vma->vm_start=2900000, old_addr=2900000, mask=-2097152): 0
can_align_down(new_vma->vm_start=5700000, new_addr=5700000, mask=-2097152): 1
=== Starting move_page_tables ===
Doing move_ptes for 2900000 -> 5700000 of extent=100000 <-- Unoptimized
Doing PUD move for 2a00000 -> 5800000 of extent=200000
Doing PUD move for 2c00000 -> 5a00000 of extent=200000
</prints>
Link: https://lkml.kernel.org/r/20230903151328.2981432-6-joel@xxxxxxxxxxxxxxxxx
Signed-off-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Reviewed-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Kalesh Singh <kaleshsingh@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill@xxxxxxxxxxxxx>
Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Lokesh Gidra <lokeshgidra@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/mm/mremap_test.c | 57 +++++++++++++++++++--
1 file changed, 52 insertions(+), 5 deletions(-)
--- a/tools/testing/selftests/mm/mremap_test.c~selftests-mm-add-a-test-for-remapping-to-area-immediately-after-existing-mapping
+++ a/tools/testing/selftests/mm/mremap_test.c
@@ -29,6 +29,7 @@ struct config {
unsigned long long dest_alignment;
unsigned long long region_size;
int overlapping;
+ int dest_preamble_size;
};
struct test {
@@ -283,7 +284,7 @@ error:
static long long remap_region(struct config c, unsigned int threshold_mb,
char pattern_seed)
{
- void *addr, *src_addr, *dest_addr;
+ void *addr, *src_addr, *dest_addr, *dest_preamble_addr;
unsigned long long i;
struct timespec t_start = {0, 0}, t_end = {0, 0};
long long start_ns, end_ns, align_mask, ret, offset;
@@ -300,7 +301,7 @@ static long long remap_region(struct con
goto out;
}
- /* Set byte pattern */
+ /* Set byte pattern for source block. */
srand(pattern_seed);
for (i = 0; i < threshold; i++)
memset((char *) src_addr + i, (char) rand(), 1);
@@ -312,6 +313,9 @@ static long long remap_region(struct con
addr = (void *) (((unsigned long long) src_addr + c.region_size
+ offset) & align_mask);
+ /* Remap after the destination block preamble. */
+ addr += c.dest_preamble_size;
+
/* See comment in get_source_mapping() */
if (!((unsigned long long) addr & c.dest_alignment))
addr = (void *) ((unsigned long long) addr | c.dest_alignment);
@@ -327,6 +331,24 @@ static long long remap_region(struct con
addr += c.dest_alignment;
}
+ if (c.dest_preamble_size) {
+ dest_preamble_addr = mmap((void *) addr - c.dest_preamble_size, c.dest_preamble_size,
+ PROT_READ | PROT_WRITE,
+ MAP_FIXED_NOREPLACE | MAP_ANONYMOUS | MAP_SHARED,
+ -1, 0);
+ if (dest_preamble_addr == MAP_FAILED) {
+ ksft_print_msg("Failed to map dest preamble region: %s\n",
+ strerror(errno));
+ ret = -1;
+ goto clean_up_src;
+ }
+
+ /* Set byte pattern for the dest preamble block. */
+ srand(pattern_seed);
+ for (i = 0; i < c.dest_preamble_size; i++)
+ memset((char *) dest_preamble_addr + i, (char) rand(), 1);
+ }
+
clock_gettime(CLOCK_MONOTONIC, &t_start);
dest_addr = mremap(src_addr, c.region_size, c.region_size,
MREMAP_MAYMOVE|MREMAP_FIXED, (char *) addr);
@@ -335,7 +357,7 @@ static long long remap_region(struct con
if (dest_addr == MAP_FAILED) {
ksft_print_msg("mremap failed: %s\n", strerror(errno));
ret = -1;
- goto clean_up_src;
+ goto clean_up_dest_preamble;
}
/* Verify byte pattern after remapping */
@@ -353,6 +375,23 @@ static long long remap_region(struct con
}
}
+ /* Verify the dest preamble byte pattern after remapping */
+ if (c.dest_preamble_size) {
+ srand(pattern_seed);
+ for (i = 0; i < c.dest_preamble_size; i++) {
+ char c = (char) rand();
+
+ if (((char *) dest_preamble_addr)[i] != c) {
+ ksft_print_msg("Preamble data after remap doesn't match at offset %d\n",
+ i);
+ ksft_print_msg("Expected: %#x\t Got: %#x\n", c & 0xff,
+ ((char *) dest_preamble_addr)[i] & 0xff);
+ ret = -1;
+ goto clean_up_dest;
+ }
+ }
+ }
+
start_ns = t_start.tv_sec * NS_PER_SEC + t_start.tv_nsec;
end_ns = t_end.tv_sec * NS_PER_SEC + t_end.tv_nsec;
ret = end_ns - start_ns;
@@ -365,6 +404,9 @@ static long long remap_region(struct con
*/
clean_up_dest:
munmap(dest_addr, c.region_size);
+clean_up_dest_preamble:
+ if (c.dest_preamble_size && dest_preamble_addr)
+ munmap(dest_preamble_addr, c.dest_preamble_size);
clean_up_src:
munmap(src_addr, c.region_size);
out:
@@ -440,7 +482,7 @@ static int parse_args(int argc, char **a
return 0;
}
-#define MAX_TEST 14
+#define MAX_TEST 15
#define MAX_PERF_TEST 3
int main(int argc, char **argv)
{
@@ -449,7 +491,7 @@ int main(int argc, char **argv)
unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;
unsigned int pattern_seed;
int num_expand_tests = 2;
- struct test test_cases[MAX_TEST];
+ struct test test_cases[MAX_TEST] = {};
struct test perf_test_cases[MAX_PERF_TEST];
int page_size;
time_t t;
@@ -510,6 +552,11 @@ int main(int argc, char **argv)
test_cases[13] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS,
"5MB mremap - Source 1MB-aligned, Destination 1MB-aligned");
+ /* Src and Dest addr 1MB aligned. 5MB mremap. */
+ test_cases[14] = MAKE_TEST(_1MB, _1MB, _5MB, NON_OVERLAPPING, EXPECT_SUCCESS,
+ "5MB mremap - Source 1MB-aligned, Dest 1MB-aligned with 40MB Preamble");
+ test_cases[14].config.dest_preamble_size = 10 * _4MB;
+
perf_test_cases[0] = MAKE_TEST(page_size, page_size, _1GB, NON_OVERLAPPING, EXPECT_SUCCESS,
"1GB mremap - Source PTE-aligned, Destination PTE-aligned");
/*
_
Patches currently in -mm which might be from joel@xxxxxxxxxxxxxxxxx are
mm-vmalloc-add-a-safer-version-of-find_vm_area-for-debug.patch
mm-mremap-optimize-the-start-addresses-in-move_page_tables.patch
mm-mremap-allow-moves-within-the-same-vma-for-stack-moves.patch
selftests-mm-fix-failure-case-when-new-remap-region-was-not-found.patch
selftests-mm-add-a-test-for-mutually-aligned-moves-pmd-size.patch
selftests-mm-add-a-test-for-remapping-to-area-immediately-after-existing-mapping.patch
selftests-mm-add-a-test-for-remapping-within-a-range.patch
selftests-mm-add-a-test-for-moving-from-an-offset-from-start-of-mapping.patch
