mm: fix mbind vma merge problem
Strangely, current mbind() doesn't merge vma with neighbor vma although it's possible.
Unfortunately, many vma can reduce performance...
This patch fixes it.
reproduced program
----------------------------------------------------------------
#include <numaif.h>
#include <numa.h>
#include <sys/mman.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
static unsigned long pagesize;
int main(int argc, char** argv)
{
void* addr;
int ch;
int node;
struct bitmask *nmask = numa_allocate_nodemask();
int err;
int node_set = 0;
char buf[128];
while ((ch = getopt(argc, argv, "n:")) != -1){
switch (ch){
case 'n':
node = strtol(optarg, NULL, 0);
numa_bitmask_setbit(nmask, node);
node_set = 1;
break;
default:
;
}
}
argc -= optind;
argv += optind;
if (!node_set)
numa_bitmask_setbit(nmask, 0);
pagesize = getpagesize();
addr = mmap(NULL, pagesize*3, PROT_READ|PROT_WRITE,
MAP_ANON|MAP_PRIVATE, 0, 0);
if (addr == MAP_FAILED)
perror("mmap "), exit(1);
fprintf(stderr, "pid = %d \n" "addr = %p\n", getpid(), addr);
/* make page populate */
memset(addr, 0, pagesize*3);
/* first mbind */
err = mbind(addr+pagesize, pagesize, MPOL_BIND, nmask->maskp,
nmask->size, MPOL_MF_MOVE_ALL);
if (err)
error("mbind1 ");
/* second mbind */
err = mbind(addr, pagesize*3, MPOL_DEFAULT, NULL, 0, 0);
if (err)
error("mbind2 ");
sprintf(buf, "cat /proc/%d/maps", getpid());
system(buf);
return 0;
}
----------------------------------------------------------------
result without this patch
addr = 0x7fe26ef09000
[snip]
7fe26ef09000-7fe26ef0a000 rw-p 00000000 00:00 0
7fe26ef0a000-7fe26ef0b000 rw-p 00000000 00:00 0
7fe26ef0b000-7fe26ef0c000 rw-p 00000000 00:00 0
7fe26ef0c000-7fe26ef0d000 rw-p 00000000 00:00 0
=> 0x7fe26ef09000-0x7fe26ef0c000 have three vmas.
result with this patch
addr = 0x7fc9ebc76000
[snip]
7fc9ebc76000-7fc9ebc7a000 rw-p 00000000 00:00 0
7fffbe690000-7fffbe6a5000 rw-p 00000000 00:00 0 [stack]
=> 0x7fc9ebc76000-0x7fc9ebc7a000 have only one vma.
[minchan.kim@gmail.com: fix file offset passed to vma_merge()]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 290fb5b..44dd9d1 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -563,24 +563,50 @@
}
/* Step 2: apply policy to a range and do splits. */
-static int mbind_range(struct vm_area_struct *vma, unsigned long start,
- unsigned long end, struct mempolicy *new)
+static int mbind_range(struct mm_struct *mm, unsigned long start,
+ unsigned long end, struct mempolicy *new_pol)
{
struct vm_area_struct *next;
- int err;
+ struct vm_area_struct *prev;
+ struct vm_area_struct *vma;
+ int err = 0;
+ pgoff_t pgoff;
+ unsigned long vmstart;
+ unsigned long vmend;
- err = 0;
- for (; vma && vma->vm_start < end; vma = next) {
+ vma = find_vma_prev(mm, start, &prev);
+ if (!vma || vma->vm_start > start)
+ return -EFAULT;
+
+ for (; vma && vma->vm_start < end; prev = vma, vma = next) {
next = vma->vm_next;
- if (vma->vm_start < start)
- err = split_vma(vma->vm_mm, vma, start, 1);
- if (!err && vma->vm_end > end)
- err = split_vma(vma->vm_mm, vma, end, 0);
- if (!err)
- err = policy_vma(vma, new);
+ vmstart = max(start, vma->vm_start);
+ vmend = min(end, vma->vm_end);
+
+ pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
+ prev = vma_merge(mm, prev, vmstart, vmend, vma->vm_flags,
+ vma->anon_vma, vma->vm_file, pgoff, new_pol);
+ if (prev) {
+ vma = prev;
+ next = vma->vm_next;
+ continue;
+ }
+ if (vma->vm_start != vmstart) {
+ err = split_vma(vma->vm_mm, vma, vmstart, 1);
+ if (err)
+ goto out;
+ }
+ if (vma->vm_end != vmend) {
+ err = split_vma(vma->vm_mm, vma, vmend, 0);
+ if (err)
+ goto out;
+ }
+ err = policy_vma(vma, new_pol);
if (err)
- break;
+ goto out;
}
+
+ out:
return err;
}
@@ -1047,7 +1073,7 @@
if (!IS_ERR(vma)) {
int nr_failed = 0;
- err = mbind_range(vma, start, end, new);
+ err = mbind_range(mm, start, end, new);
if (!list_empty(&pagelist))
nr_failed = migrate_pages(&pagelist, new_vma_page,