mm: fix the NULL mapping case in __isolate_lru_page()
George Boole would have noticed a slight error in 4.16 commit69d763fc6d
("mm: pin address_space before dereferencing it while isolating an LRU page"). Fix it, to match both the comment above it, and the original behaviour. Although anonymous pages are not marked PageDirty at first, we have an old habit of calling SetPageDirty when a page is removed from swap cache: so there's a category of ex-swap pages that are easily migratable, but were inadvertently excluded from compaction's async migration in 4.16. Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1805302014001.12558@eggly.anvils Fixes:69d763fc6d
("mm: pin address_space before dereferencing it while isolating an LRU page") Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Mel Gorman <mgorman@techsingularity.net> Reported-by: Ivan Kalvachev <ikalvachev@gmail.com> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Jan Kara <jack@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1418,7 +1418,7 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode)
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return ret;
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mapping = page_mapping(page);
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migrate_dirty = mapping && mapping->a_ops->migratepage;
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migrate_dirty = !mapping || mapping->a_ops->migratepage;
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unlock_page(page);
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if (!migrate_dirty)
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return ret;
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