FAILED: patch "[PATCH] hugetlb: fix update_and_free_page contig page struct" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From dbfee5aee7e54f83d96ceb8e3e80717fac62ad63 Mon Sep 17 00:00:00 2001
From: Mike Kravetz <[email protected]>
Date: Wed, 24 Feb 2021 12:07:50 -0800
Subject: [PATCH] hugetlb: fix update_and_free_page contig page struct
assumption
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

page structs are not guaranteed to be contiguous for gigantic pages. The routine update_and_free_page can encounter a gigantic page, yet it assumes page structs are contiguous when setting page flags in subpages.

If update_and_free_page encounters non-contiguous page structs, we can see “BUG: Bad page state in process …” errors.

Non-contiguous page structs are generally not an issue. However, they can exist with a specific kernel configuration and hotplug operations. For
example: Configure the kernel with CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where the gigantic page will be allocated. Zi Yan outlined steps to reproduce here [1].

[1] https://lore.kernel.org/linux-mm/[email protected]/

index 6786b313e6ac..3f6a50373d4f 100644
@@ -1321,14 +1321,16 @@ static inline void destroy_compound_gigantic_page(struct page *page,
 static void update_and_free_page(struct hstate *h, struct page *page)
 {
 	int i;
+	struct page *subpage = page;
 
 	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
 		return;
 
 	h->nr_huge_pages--;
 	h->nr_huge_pages_node[page_to_nid(page)]--;
-	for (i = 0; i < pages_per_huge_page(h); i++) {
-		page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
+	for (i = 0; i < pages_per_huge_page(h);
+	     i++, subpage = mem_map_next(subpage, page, i)) {
+		subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
 				1 << PG_referenced | 1 << PG_dirty |
 				1 << PG_active | 1 << PG_private |
 				1 << PG_writeback);

From b6dec027a8967feb788e14f3bbd57f318005001f Mon Sep 17 00:00:00 2001
From: Mike Kravetz <[email protected]>
Date: Mon, 1 Mar 2021 18:12:38 -0800
Subject: [PATCH] hugetlb: fix update_and_free_page contig page struct
assumption
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit dbfee5aee7e54f83d96ceb8e3e80717fac62ad63 upstream.

page structs are not guaranteed to be contiguous for gigantic pages. The routine update_and_free_page can encounter a gigantic page, yet it assumes page structs are contiguous when setting page flags in subpages.

If update_and_free_page encounters non-contiguous page structs, we can see “BUG: Bad page state in process …” errors.

Non-contiguous page structs are generally not an issue. However, they can exist with a specific kernel configuration and hotplug operations. For
example: Configure the kernel with CONFIG_SPARSEMEM and !CONFIG_SPARSEMEM_VMEMMAP. Then, hotplug add memory for the area where the gigantic page will be allocated.
Zi Yan outlined steps to reproduce here [1].

[1] https://lore.kernel.org/linux-mm/[email protected]/

---
 mm/hugetlb.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

index df89aed02302..49026c9f8570 100644
@@ -1171,14 +1171,16 @@ static inline void destroy_compound_gigantic_page(struct page *page,
 static void update_and_free_page(struct hstate *h, struct page *page)
 {
 	int i;
+	struct page *subpage = page;
 
 	if (hstate_is_gigantic(h) && !gigantic_page_supported())
 		return;
 
 	h->nr_huge_pages--;
 	h->nr_huge_pages_node[page_to_nid(page)]--;
-	for (i = 0; i < pages_per_huge_page(h); i++) {
-		page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
+	for (i = 0; i < pages_per_huge_page(h);
+	     i++, subpage = mem_map_next(subpage, page, i)) {
+		subpage->flags &= ~(1 << PG_locked | 1 << PG_error |
 				1 << PG_referenced | 1 << PG_dirty |
 				1 << PG_active | 1 << PG_private |
 				1 << PG_writeback);

2.29.2

Queued up everywhere, thanks.

greg k-h