[patch 146/262] mm/page_isolation: fix potential missing call to unset_migratetype_isolate()

Andrew Morton
2021-11-05T20:52:06Z

From: Miaohe Lin <linmiaohe@huawei.com>
Subject: mm/page_isolation: fix potential missing call to unset_migratetype_isolate()

In start_isolate_page_range() undo path, pfn_to_online_page() just checks
the first pfn in a pageblock while __first_valid_page() will traverse the
pageblock until the first online pfn is found. So we may miss the call to
unset_migratetype_isolate() in undo path and pages will remain isolated
unexpectedly. Fix this by calling undo_isolate_page_range() and this will
also help to simplify the code further. Note we shouldn't ever trigger it
because MAX_ORDER-1 aligned pfn ranges shouldn't contain memory holes now.

Link: https://lkml.kernel.org/r/20210914114348.15569-1-linmiaohe@huawei.com
Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/page_isolation.c | 20 +++-----------------
1 file changed, 3 insertions(+), 17 deletions(-)

--- a/mm/page_isolation.c~mm-page_isolation-fix-potential-missing-call-to-unset_migratetype_isolate
+++ a/mm/page_isolation.c
@@ -183,7 +183,6 @@ int start_isolate_page_range(unsigned lo
unsigned migratetype, int flags)
{
unsigned long pfn;
- unsigned long undo_pfn;
struct page *page;

BUG_ON(!IS_ALIGNED(start_pfn, pageblock_nr_pages));
@@ -193,25 +192,12 @@ int start_isolate_page_range(unsigned lo
pfn < end_pfn;
pfn += pageblock_nr_pages) {
page = __first_valid_page(pfn, pageblock_nr_pages);
- if (page) {
- if (set_migratetype_isolate(page, migratetype, flags)) {
- undo_pfn = pfn;
- goto undo;
- }
+ if (page && set_migratetype_isolate(page, migratetype, flags)) {
+ undo_isolate_page_range(start_pfn, pfn, migratetype);
+ return -EBUSY;
}
}
return 0;
-undo:
- for (pfn = start_pfn;
- pfn < undo_pfn;
- pfn += pageblock_nr_pages) {
- struct page *page = pfn_to_online_page(pfn);
- if (!page)
- continue;
- unset_migratetype_isolate(page, migratetype);
- }
-
- return -EBUSY;
}

/*
_