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Subject[PATCH 09/13] mm: __first_valid_page skip over offline pages
Date
From: Michal Hocko <mhocko@suse.com>

__first_valid_page skips over invalid pfns in the range but it might
still stumble over offline pages. At least start_isolate_page_range
will mark those set_migratetype_isolate. This doesn't represent
any immediate AFAICS because alloc_contig_range will fail to isolate
those pages but it relies on not fully initialized page which will
become a problem later when we stop associating offline pages to zones.
So this is more a preparatory patch than a fix.

Signed-off-by: Michal Hocko <mhocko@suse.com>
---
mm/page_isolation.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 5092e4ef00c8..3606104893e0 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -138,12 +138,18 @@ static inline struct page *
__first_valid_page(unsigned long pfn, unsigned long nr_pages)
{
int i;
- for (i = 0; i < nr_pages; i++)
- if (pfn_valid_within(pfn + i))
- break;
- if (unlikely(i == nr_pages))
- return NULL;
- return pfn_to_page(pfn + i);
+
+ for (i = 0; i < nr_pages; i++) {
+ struct page *page;
+
+ if (!pfn_valid_within(pfn + i))
+ continue;
+ page = pfn_to_online_page(pfn + i);
+ if (!page)
+ continue;
+ return page;
+ }
+ return NULL;
}

/*
@@ -184,8 +190,12 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
undo:
for (pfn = start_pfn;
pfn < undo_pfn;
- pfn += pageblock_nr_pages)
- unset_migratetype_isolate(pfn_to_page(pfn), migratetype);
+ pfn += pageblock_nr_pages) {
+ struct page *page = pfn_to_online_page(pfn);
+ if (!page)
+ continue;
+ unset_migratetype_isolate(page, migratetype);
+ }

return -EBUSY;
}
--
2.11.0
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