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mm: add merging after mremap resize

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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.

[akpm@linux-foundation.org: coding-style cleanups]
Link: https://lkml.kernel.org/r/20220603145719.1012094-3-matenajakub@gmail.com
Signed-off-by: Jakub Matěna <matenajakub@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jakub Matěna 2022-06-03 16:57:19 +02:00 committed by Andrew Morton
parent eef199440d
commit ca3d76b0aa
2 changed files with 65 additions and 3 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

19
mm/mremap.c
View file

@ -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>
@ -1012,6 +1014,9 @@ 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)) {
@ -1020,8 +1025,18 @@ 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;

49
tools/testing/selftests/vm/mremap_test.c
View file

@ -118,6 +118,50 @@ 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 +380,7 @@ 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 +452,14 @@ 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:");