The patch titled Subject: mm/page_alloc: correct start page when guard page debug is enabled has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-page_alloc-correct-start-page-when-guard-page-debug-is-enabled.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's

*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days

------------------------------------------------------ From: Kemeng Shi shikemeng@huaweicloud.com Subject: mm/page_alloc: correct start page when guard page debug is enabled Date: Wed, 27 Sep 2023 17:44:01 +0800

When guard page debug is enabled and set_page_guard returns success, we miss to forward page to point to start of next split range and we will do split unexpectedly in page range without target page. Move start page update before set_page_guard to fix this.

As we split to wrong target page, then splited pages are not able to merge back to original order when target page is put back and splited pages except target page is not usable. To be specific:

Consider target page is the third page in buddy page with order 2. | buddy-2 | Page | Target | Page |

After break down to target page, we will only set first page to Guard because of bug. | Guard | Page | Target | Page |

When we try put_page_back_buddy with target page, the buddy page of target if neither guard nor buddy, Then it's not able to construct original page with order 2 | Guard | Page | buddy-0 | Page |

All pages except target page is not in free list and is not usable.

Link: https://lkml.kernel.org/r/20230927094401.68205-1-shikemeng@huaweicloud.com Fixes: 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages") Signed-off-by: Kemeng Shi shikemeng@huaweicloud.com Acked-by: Naoya Horiguchi naoya.horiguchi@nec.com Cc: Matthew Wilcox (Oracle) willy@infradead.org Cc: Oscar Salvador osalvador@suse.de Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/page_alloc.c~mm-page_alloc-correct-start-page-when-guard-page-debug-is-enabled +++ a/mm/page_alloc.c @@ -6475,6 +6475,7 @@ static void break_down_buddy_pages(struc next_page = page; current_buddy = page + size; } + page = next_page;

if (set_page_guard(zone, current_buddy, high, migratetype)) continue; @@ -6482,7 +6483,6 @@ static void break_down_buddy_pages(struc if (current_buddy != target) { add_to_free_list(current_buddy, zone, high, migratetype); set_buddy_order(current_buddy, high); - page = next_page; } } } _

Patches currently in -mm which might be from shikemeng@huaweicloud.com are

mm-page_alloc-correct-start-page-when-guard-page-debug-is-enabled.patch mm-compaction-use-correct-list-in-move_freelist_head-tail.patch mm-compaction-call-list_is_first-last-more-intuitively-in-move_freelist_head-tail.patch mm-compaction-correctly-return-failure-with-bogus-compound_order-in-strict-mode.patch mm-compaction-remove-repeat-compact_blockskip_flush-check-in-reset_isolation_suitable.patch mm-compaction-improve-comment-of-is_via_compact_memory.patch mm-compaction-factor-out-code-to-test-if-we-should-run-compaction-for-target-order.patch