When mremap call results in expansion, it might be possible to merge the
VMA with the next VMA which might become adjacent. This patch adds
vma_merge call after the expansion is done to try and merge.
Signed-off-by: Jakub Matěna <matenajakub@xxxxxxxxx>
---
mm/mremap.c | 19 +++++++++-
tools/testing/selftests/vm/mremap_test.c | 47 +++++++++++++++++++++++-
2 files changed, 63 insertions(+), 3 deletions(-)
diff --git a/mm/mremap.c b/mm/mremap.c
index 0b93fac76851..66970dcd636a 100644
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -9,6 +9,7 @@
*/
#include <linux/mm.h>
+#include <linux/mm_inline.h>
#include <linux/hugetlb.h>
#include <linux/shm.h>
#include <linux/ksm.h>
@@ -23,6 +24,7 @@
#include <linux/mmu_notifier.h>
#include <linux/uaccess.h>
#include <linux/userfaultfd_k.h>
+#include <linux/mempolicy.h>
#include <asm/cacheflush.h>
#include <asm/tlb.h>
@@ -1014,6 +1016,9 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
/* can we just expand the current mapping? */
if (vma_expandable(vma, new_len - old_len)) {
long pages = (new_len - old_len) >> PAGE_SHIFT;
+ unsigned long extension_start = addr + old_len;
+ unsigned long extension_end = addr + new_len;
+ pgoff_t extension_pgoff = vma->vm_pgoff + (old_len >> PAGE_SHIFT);
if (vma->vm_flags & VM_ACCOUNT) {
if (security_vm_enough_memory_mm(mm, pages)) {
@@ -1022,8 +1027,18 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
}
}
- if (vma_adjust(vma, vma->vm_start, addr + new_len,
- vma->vm_pgoff, NULL)) {
+ /*
+ * Function vma_merge() is called on the extension we are adding to
+ * the already existing vma, vma_merge() will merge this extension with
+ * the already existing vma (expand operation itself) and possibly also
+ * with the next vma if it becomes adjacent to the expanded vma and
+ * otherwise compatible.
+ */
+ vma = vma_merge(mm, vma, extension_start, extension_end,
+ vma->vm_flags, vma->anon_vma, vma->vm_file,
+ extension_pgoff, vma_policy(vma),
+ vma->vm_userfaultfd_ctx, anon_vma_name(vma));
+ if (!vma) {
vm_unacct_memory(pages);
ret = -ENOMEM;
goto out;
diff --git a/tools/testing/selftests/vm/mremap_test.c b/tools/testing/selftests/vm/mremap_test.c
index db0270127aeb..0865a6cb5bdb 100644
--- a/tools/testing/selftests/vm/mremap_test.c
+++ b/tools/testing/selftests/vm/mremap_test.c
@@ -118,6 +118,48 @@ static unsigned long long get_mmap_min_addr(void)
return addr;
}
+/*
+ * This test validates that merge is called when expanding a mapping.
+ * Mapping containing three pages is created, middle page is unmapped
+ * and then the mapping containing the first page is expanded so that
+ * it fills the created hole. The two parts should merge creating
+ * single mapping with three pages.
+ */
+static void mremap_expand_merge(unsigned long page_size)
+{
+ char *test_name = "mremap expand merge";
+ FILE *fp;
+ char *line = NULL;
+ size_t len = 0;
+ bool success = false;
+
+ char *start = mmap(NULL, 3 * page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ munmap(start + page_size, page_size);
+ mremap(start, page_size, 2 * page_size, 0);
+
+ fp = fopen("/proc/self/maps", "r");
+ if (fp == NULL) {
+ ksft_test_result_fail("%s\n", test_name);
+ return;
+ }
+
+ while(getline(&line, &len, fp) != -1) {
+ char *first = strtok(line,"- ");
+ void *first_val = (void *) strtol(first, NULL, 16);
+ char *second = strtok(NULL,"- ");
+ void *second_val = (void *) strtol(second, NULL, 16);
+ if (first_val == start && second_val == start + 3 * page_size) {
+ success = true;
+ break;
+ }
+ }
+ if (success)
+ ksft_test_result_pass("%s\n", test_name);
+ else
+ ksft_test_result_fail("%s\n", test_name);
+ fclose(fp);
+}
+
/*
* Returns the start address of the mapping on success, else returns
* NULL on failure.
@@ -336,6 +378,7 @@ int main(int argc, char **argv)
int i, run_perf_tests;
unsigned int threshold_mb = VALIDATION_DEFAULT_THRESHOLD;
unsigned int pattern_seed;
+ int num_expand_tests = 1;
struct test test_cases[MAX_TEST];
struct test perf_test_cases[MAX_PERF_TEST];
int page_size;
@@ -407,12 +450,14 @@ int main(int argc, char **argv)
(threshold_mb * _1MB >= _1GB);
ksft_set_plan(ARRAY_SIZE(test_cases) + (run_perf_tests ?
- ARRAY_SIZE(perf_test_cases) : 0));
+ ARRAY_SIZE(perf_test_cases) : 0) + num_expand_tests);
for (i = 0; i < ARRAY_SIZE(test_cases); i++)
run_mremap_test_case(test_cases[i], &failures, threshold_mb,
pattern_seed);
+ mremap_expand_merge(page_size);
+
if (run_perf_tests) {
ksft_print_msg("\n%s\n",
"mremap HAVE_MOVE_PMD/PUD optimization time comparison for 1GB region:");
--
2.35.1
