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-rw-r--r--mm/hugetlb.c62
1 files changed, 23 insertions, 39 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index f260ffa26363..7dc80cbe8e89 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1540,62 +1540,46 @@ int dissolve_free_huge_pages(unsigned long start_pfn, unsigned long end_pfn)
static struct page *__alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
int nid, nodemask_t *nmask)
{
- struct page *page;
- unsigned int r_nid;
+ struct page *page = NULL;
if (hstate_is_gigantic(h))
return NULL;
- /*
- * Assume we will successfully allocate the surplus page to
- * prevent racing processes from causing the surplus to exceed
- * overcommit
- *
- * This however introduces a different race, where a process B
- * tries to grow the static hugepage pool while alloc_pages() is
- * called by process A. B will only examine the per-node
- * counters in determining if surplus huge pages can be
- * converted to normal huge pages in adjust_pool_surplus(). A
- * won't be able to increment the per-node counter, until the
- * lock is dropped by B, but B doesn't drop hugetlb_lock until
- * no more huge pages can be converted from surplus to normal
- * state (and doesn't try to convert again). Thus, we have a
- * case where a surplus huge page exists, the pool is grown, and
- * the surplus huge page still exists after, even though it
- * should just have been converted to a normal huge page. This
- * does not leak memory, though, as the hugepage will be freed
- * once it is out of use. It also does not allow the counters to
- * go out of whack in adjust_pool_surplus() as we don't modify
- * the node values until we've gotten the hugepage and only the
- * per-node value is checked there.
- */
spin_lock(&hugetlb_lock);
- if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
- spin_unlock(&hugetlb_lock);
- return NULL;
- } else {
- h->nr_huge_pages++;
- h->surplus_huge_pages++;
- }
+ if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages)
+ goto out_unlock;
spin_unlock(&hugetlb_lock);
page = __hugetlb_alloc_buddy_huge_page(h, gfp_mask, nid, nmask);
+ if (!page)
+ goto out_unlock;
spin_lock(&hugetlb_lock);
- if (page) {
+ /*
+ * We could have raced with the pool size change.
+ * Double check that and simply deallocate the new page
+ * if we would end up overcommiting the surpluses. Abuse
+ * temporary page to workaround the nasty free_huge_page
+ * codeflow
+ */
+ if (h->surplus_huge_pages >= h->nr_overcommit_huge_pages) {
+ SetPageHugeTemporary(page);
+ put_page(page);
+ page = NULL;
+ } else {
+ int r_nid;
+
+ h->surplus_huge_pages++;
+ h->nr_huge_pages++;
INIT_LIST_HEAD(&page->lru);
r_nid = page_to_nid(page);
set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
set_hugetlb_cgroup(page, NULL);
- /*
- * We incremented the global counters already
- */
h->nr_huge_pages_node[r_nid]++;
h->surplus_huge_pages_node[r_nid]++;
- } else {
- h->nr_huge_pages--;
- h->surplus_huge_pages--;
}
+
+out_unlock:
spin_unlock(&hugetlb_lock);
return page;