lkml.org 
[lkml]   [2017]   [Sep]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] mm, hugetlb, soft_offline: save compound page order before page migration
This fixes a bug in madvise() where if you'd try to soft offline a
hugepage via madvise(), while walking the address range you'd end up,
using the wrong page offset due to attempting to get the compound
order of a former but presently not compound page, due to dissolving
the huge page (since c3114a8).

Signed-off-by: Alexandru Moise <00moses.alexander00@gmail.com>
---
mm/madvise.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 21261ff0466f..25bade36e9ca 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -625,18 +625,26 @@ static int madvise_inject_error(int behavior,
{
struct page *page;
struct zone *zone;
+ unsigned int order;

if (!capable(CAP_SYS_ADMIN))
return -EPERM;

- for (; start < end; start += PAGE_SIZE <<
- compound_order(compound_head(page))) {
+
+ for (; start < end; start += PAGE_SIZE << order) {
int ret;

ret = get_user_pages_fast(start, 1, 0, &page);
if (ret != 1)
return ret;

+ /*
+ * When soft offlining hugepages, after migrating the page
+ * we dissolve it, therefore in the second loop "page" will
+ * no longer be a compound page, and order will be 0.
+ */
+ order = compound_order(compound_head(page));
+
if (PageHWPoison(page)) {
put_page(page);
continue;
--
2.14.1
\
 
 \ /
  Last update: 2017-09-12 22:43    [W:0.112 / U:2.820 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site