From: Hugh Dickins <hughd@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
Liam Howlett <liam.howlett@oracle.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: [PATCH mmotm] mempolicy: mbind_range() set_policy() after vma_merge()
Date: Thu, 3 Mar 2022 20:36:37 -0800 (PST) [thread overview]
Message-ID: <319e4db9-64ae-4bca-92f0-ade85d342ff@google.com> (raw)
v2.6.34 commit 9d8cebd4bcd7 ("mm: fix mbind vma merge problem")
introduced vma_merge() to mbind_range(); but unlike madvise, mlock and
mprotect, it put a "continue" to next vma where its precedents go to
update flags on current vma before advancing: that left vma with the
wrong setting in the infamous vma_merge() case 8.
v3.10 commit 1444f92c8498 ("mm: merging memory blocks resets mempolicy")
tried to fix that in vma_adjust(), without fully understanding the issue.
v3.11 commit 3964acd0dbec ("mm: mempolicy: fix mbind_range() &&
vma_adjust() interaction") reverted that, and went about the fix in the
right way, but chose to optimize out an unnecessary mpol_dup() with a
prior mpol_equal() test. But on tmpfs, that also pessimized out the
vital call to its ->set_policy(), leaving the new mbind unenforced.
Just delete that optimization now (though it could be made conditional
on vma not having a set_policy). Also remove the "next" variable:
it turned out to be blameless, but also pointless.
Fixes: 3964acd0dbec ("mm: mempolicy: fix mbind_range() && vma_adjust() interaction")
Signed-off-by: Hugh Dickins <hughd@google.com>
---
mm/mempolicy.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -786,7 +786,6 @@ static int vma_replace_policy(struct vm_area_struct *vma,
static int mbind_range(struct mm_struct *mm, unsigned long start,
unsigned long end, struct mempolicy *new_pol)
{
- struct vm_area_struct *next;
struct vm_area_struct *prev;
struct vm_area_struct *vma;
int err = 0;
@@ -801,8 +800,7 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
if (start > vma->vm_start)
prev = vma;
- for (; vma && vma->vm_start < end; prev = vma, vma = next) {
- next = vma->vm_next;
+ for (; vma && vma->vm_start < end; prev = vma, vma = vma->vm_next) {
vmstart = max(start, vma->vm_start);
vmend = min(end, vma->vm_end);
@@ -817,10 +815,6 @@ static int mbind_range(struct mm_struct *mm, unsigned long start,
anon_vma_name(vma));
if (prev) {
vma = prev;
- next = vma->vm_next;
- if (mpol_equal(vma_policy(vma), new_pol))
- continue;
- /* vma_merge() joined vma && vma->next, case 8 */
goto replace;
}
if (vma->vm_start != vmstart) {
next reply other threads:[~2022-03-04 4:36 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-04 4:36 Hugh Dickins [this message]
2022-03-04 18:06 ` [PATCH mmotm] mempolicy: mbind_range() set_policy() after vma_merge() Oleg Nesterov
2022-03-04 22:33 ` Hugh Dickins
2022-03-04 18:49 ` Liam Howlett
2022-03-04 19:05 ` Liam Howlett
2022-03-04 22:48 ` Hugh Dickins
2022-03-05 2:00 ` Liam Howlett
2022-03-05 2:28 ` Hugh Dickins
2022-03-08 16:05 ` Liam Howlett
2022-03-08 21:32 ` Hugh Dickins
2022-03-09 12:41 ` Vlastimil Babka
2022-03-09 19:10 ` Liam Howlett
2022-03-11 9:33 ` Hugh Dickins
2022-03-11 8:54 ` Hugh Dickins
2022-03-11 12:47 ` Vlastimil Babka
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=319e4db9-64ae-4bca-92f0-ade85d342ff@google.com \
--to=hughd@google.com \
--cc=akpm@linux-foundation.org \
--cc=liam.howlett@oracle.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=oleg@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).