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Subject[PATCH 5.15 102/128] mm: mempolicy: fix THP allocations escaping mempolicy restrictions
Date
From: Andrey Ryabinin <arbn@yandex-team.com>

commit 338635340669d5b317c7e8dcf4fff4a0f3651d87 upstream.

alloc_pages_vma() may try to allocate THP page on the local NUMA node
first:

page = __alloc_pages_node(hpage_node,
gfp | __GFP_THISNODE | __GFP_NORETRY, order);

And if the allocation fails it retries allowing remote memory:

if (!page && (gfp & __GFP_DIRECT_RECLAIM))
page = __alloc_pages_node(hpage_node,
gfp, order);

However, this retry allocation completely ignores memory policy nodemask
allowing allocation to escape restrictions.

The first appearance of this bug seems to be the commit ac5b2c18911f
("mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings").

The bug disappeared later in the commit 89c83fb539f9 ("mm, thp:
consolidate THP gfp handling into alloc_hugepage_direct_gfpmask") and
reappeared again in slightly different form in the commit 76e654cc91bb
("mm, page_alloc: allow hugepage fallback to remote nodes when
madvised")

Fix this by passing correct nodemask to the __alloc_pages() call.

The demonstration/reproducer of the problem:

$ mount -oremount,size=4G,huge=always /dev/shm/
$ echo always > /sys/kernel/mm/transparent_hugepage/defrag
$ cat mbind_thp.c
#include <unistd.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <assert.h>
#include <stdlib.h>
#include <stdio.h>
#include <numaif.h>

#define SIZE 2ULL << 30
int main(int argc, char **argv)
{
int fd;
unsigned long long i;
char *addr;
pid_t pid;
char buf[100];
unsigned long nodemask = 1;

fd = open("/dev/shm/test", O_RDWR|O_CREAT);
assert(fd > 0);
assert(ftruncate(fd, SIZE) == 0);

addr = mmap(NULL, SIZE, PROT_READ|PROT_WRITE,
MAP_SHARED, fd, 0);

assert(mbind(addr, SIZE, MPOL_BIND, &nodemask, 2, MPOL_MF_STRICT|MPOL_MF_MOVE)==0);
for (i = 0; i < SIZE; i+=4096) {
addr[i] = 1;
}
pid = getpid();
snprintf(buf, sizeof(buf), "grep shm /proc/%d/numa_maps", pid);
system(buf);
sleep(10000);

return 0;
}
$ gcc mbind_thp.c -o mbind_thp -lnuma
$ numactl -H
available: 2 nodes (0-1)
node 0 cpus: 0 2
node 0 size: 1918 MB
node 0 free: 1595 MB
node 1 cpus: 1 3
node 1 size: 2014 MB
node 1 free: 1731 MB
node distances:
node 0 1
0: 10 20
1: 20 10
$ rm -f /dev/shm/test; taskset -c 0 ./mbind_thp
7fd970a00000 bind:0 file=/dev/shm/test dirty=524288 active=0 N0=396800 N1=127488 kernelpagesize_kB=4

Link: https://lkml.kernel.org/r/20211208165343.22349-1-arbn@yandex-team.com
Fixes: ac5b2c18911f ("mm: thp: relax __GFP_THISNODE for MADV_HUGEPAGE mappings")
Signed-off-by: Andrey Ryabinin <arbn@yandex-team.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/mempolicy.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2140,8 +2140,7 @@ struct page *alloc_pages_vma(gfp_t gfp,
* memory with both reclaim and compact as well.
*/
if (!page && (gfp & __GFP_DIRECT_RECLAIM))
- page = __alloc_pages_node(hpage_node,
- gfp, order);
+ page = __alloc_pages(gfp, order, hpage_node, nmask);

goto out;
}

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