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authorNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>2015-04-16 02:14:38 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-16 02:35:19 +0300
commitbcc54222309c70ebcb6c69c156fba4a13dee0a3b (patch)
tree2d947c66bdc0391d5294dd5fdd87cbabfa032020 /mm/hugetlb.c
parent822fc61367f062d36c5b5a4d517e9bd2b65a741f (diff)
downloadlinux-bcc54222309c70ebcb6c69c156fba4a13dee0a3b.tar.xz
mm: hugetlb: introduce page_huge_active
We are not safe from calling isolate_huge_page() on a hugepage concurrently, which can make the victim hugepage in invalid state and results in BUG_ON(). The root problem of this is that we don't have any information on struct page (so easily accessible) about hugepages' activeness. Note that hugepages' activeness means just being linked to hstate->hugepage_activelist, which is not the same as normal pages' activeness represented by PageActive flag. Normal pages are isolated by isolate_lru_page() which prechecks PageLRU before isolation, so let's do similarly for hugetlb with a new paeg_huge_active(). set/clear_page_huge_active() should be called within hugetlb_lock. But hugetlb_cow() and hugetlb_no_page() don't do this, being justified because in these functions set_page_huge_active() is called right after the hugepage is allocated and no other thread tries to isolate it. [akpm@linux-foundation.org: s/PageHugeActive/page_huge_active/, make it return bool] [fengguang.wu@intel.com: set_page_huge_active() can be static] Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> Cc: Hugh Dickins <hughd@google.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Mel Gorman <mgorman@suse.de> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/hugetlb.c')
-rw-r--r--mm/hugetlb.c41
1 files changed, 38 insertions, 3 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 995c8d65a95c..05407831016b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -924,6 +924,31 @@ struct hstate *size_to_hstate(unsigned long size)
return NULL;
}
+/*
+ * Test to determine whether the hugepage is "active/in-use" (i.e. being linked
+ * to hstate->hugepage_activelist.)
+ *
+ * This function can be called for tail pages, but never returns true for them.
+ */
+bool page_huge_active(struct page *page)
+{
+ VM_BUG_ON_PAGE(!PageHuge(page), page);
+ return PageHead(page) && PagePrivate(&page[1]);
+}
+
+/* never called for tail page */
+static void set_page_huge_active(struct page *page)
+{
+ VM_BUG_ON_PAGE(!PageHeadHuge(page), page);
+ SetPagePrivate(&page[1]);
+}
+
+static void clear_page_huge_active(struct page *page)
+{
+ VM_BUG_ON_PAGE(!PageHeadHuge(page), page);
+ ClearPagePrivate(&page[1]);
+}
+
void free_huge_page(struct page *page)
{
/*
@@ -952,6 +977,7 @@ void free_huge_page(struct page *page)
restore_reserve = true;
spin_lock(&hugetlb_lock);
+ clear_page_huge_active(page);
hugetlb_cgroup_uncharge_page(hstate_index(h),
pages_per_huge_page(h), page);
if (restore_reserve)
@@ -2972,6 +2998,7 @@ retry_avoidcopy:
copy_user_huge_page(new_page, old_page, address, vma,
pages_per_huge_page(h));
__SetPageUptodate(new_page);
+ set_page_huge_active(new_page);
mmun_start = address & huge_page_mask(h);
mmun_end = mmun_start + huge_page_size(h);
@@ -3084,6 +3111,7 @@ retry:
}
clear_huge_page(page, address, pages_per_huge_page(h));
__SetPageUptodate(page);
+ set_page_huge_active(page);
if (vma->vm_flags & VM_MAYSHARE) {
int err;
@@ -3913,19 +3941,26 @@ int dequeue_hwpoisoned_huge_page(struct page *hpage)
bool isolate_huge_page(struct page *page, struct list_head *list)
{
+ bool ret = true;
+
VM_BUG_ON_PAGE(!PageHead(page), page);
- if (!get_page_unless_zero(page))
- return false;
spin_lock(&hugetlb_lock);
+ if (!page_huge_active(page) || !get_page_unless_zero(page)) {
+ ret = false;
+ goto unlock;
+ }
+ clear_page_huge_active(page);
list_move_tail(&page->lru, list);
+unlock:
spin_unlock(&hugetlb_lock);
- return true;
+ return ret;
}
void putback_active_hugepage(struct page *page)
{
VM_BUG_ON_PAGE(!PageHead(page), page);
spin_lock(&hugetlb_lock);
+ set_page_huge_active(page);
list_move_tail(&page->lru, &(page_hstate(page))->hugepage_activelist);
spin_unlock(&hugetlb_lock);
put_page(page);