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/mm-page_alloc-correct-start-page-when-guard-page-debug-is-enabled.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Fixes: 06be6ff3d2ec ("mm,hwpoison: rework soft offline for free pages")
Signed-off-by: Kemeng Shi <shikemeng@xxxxxxxxxxxxxxx>
Acked-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxxxx 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
