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

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Date:   Mon, 18 Apr 2022 14:12:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 5.17 179/219] hugetlb: do not demote poisoned hugetlb pages

From: Mike Kravetz <mike.kravetz@...cle.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@...cle.com>
Reviewed-by: Naoya Horiguchi <naoya.horiguchi@....com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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) \