path: root/mm
diff options
authorDavid Rientjes <rientjes@google.com>2015-03-12 16:25:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-03-12 18:46:07 -0700
commit44fc80573cc760a7154f41fd0a958ee10eba1a81 (patch)
tree2d3fd80fa0bc653b2be577e38ef38217727acd22 /mm
parentmm, oom: do not fail __GFP_NOFAIL allocation if oom killer is disabled (diff)
mm, hugetlb: close race when setting PageTail for gigantic pages
Now that gigantic pages are dynamically allocatable, care must be taken to ensure that p->first_page is valid before setting PageTail. If this isn't done, then it is possible to race and have compound_head() return NULL. Signed-off-by: David Rientjes <rientjes@google.com> Acked-by: Davidlohr Bueso <dave@stgolabs.net> Cc: Luiz Capitulino <lcapitulino@redhat.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
1 files changed, 3 insertions, 1 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 0a9ac6c26832..c41b2a0ee273 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -917,7 +917,6 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
- __SetPageTail(p);
* For gigantic hugepages allocated through bootmem at
* boot, it's safer to be consistent with the not-gigantic
@@ -933,6 +932,9 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
set_page_count(p, 0);
p->first_page = page;
+ /* Make sure p->first_page is always valid for PageTail() */
+ smp_wmb();
+ __SetPageTail(p);