[PATCH 5.17 179/219] hugetlb: do not demote poisoned hugetlb pages

Greg Kroah-Hartman
2022-04-18T12:39:28Z

From: Mike Kravetz <mike.kravetz@oracle.com>

commit 5a317412ef884763fdf7aa17f9f3636959d11d8f upstream.

It is possible for poisoned hugetlb pages to reside on the free lists.
The huge page allocation routines which dequeue entries from the free
lists make a point of avoiding poisoned pages. There is no such check
and avoidance in the demote code path.

If a hugetlb page on the is on a free list, poison will only be set in
the head page rather then the page with the actual error. If such a
page is demoted, then the poison flag may follow the wrong page. A page
without error could have poison set, and a page with poison could not
have the flag set.

Check for poison before attempting to demote a hugetlb page. Also,
return -EBUSY to the caller if only poisoned pages are on the free list.

Link: https://lkml.kernel.org/r/20220307215707.50916-1-mike.kravetz@oracle.com
Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/hugetlb.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3469,7 +3469,6 @@ static int demote_pool_huge_page(struct
{
int nr_nodes, node;
struct page *page;
- int rc = 0;

lockdep_assert_held(&hugetlb_lock);

@@ -3480,15 +3479,19 @@ static int demote_pool_huge_page(struct
}

for_each_node_mask_to_free(h, nr_nodes, node, nodes_allowed) {
- if (!list_empty(&h->hugepage_freelists[node])) {
- page = list_entry(h->hugepage_freelists[node].next,
- struct page, lru);
- rc = demote_free_huge_page(h, page);
- break;
+ list_for_each_entry(page, &h->hugepage_freelists[node], lru) {
+ if (PageHWPoison(page))
+ continue;
+
+ return demote_free_huge_page(h, page);
}
}

- return rc;
+ /*
+ * Only way to get here is if all pages on free lists are poisoned.
+ * Return -EBUSY so that caller will not retry.
+ */
+ return -EBUSY;
}

#define HSTATE_ATTR_RO(_name) \