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	mm: compaction: make isolate_lru_page() filter-aware again
Commit 39deaf85 ("mm: compaction: make isolate_lru_page() filter-aware")
noted that compaction does not migrate dirty or writeback pages and that
is was meaningless to pick the page and re-add it to the LRU list.  This
had to be partially reverted because some dirty pages can be migrated by
compaction without blocking.
This patch updates "mm: compaction: make isolate_lru_page" by skipping
over pages that migration has no possibility of migrating to minimise LRU
disruption.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel<riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andy Isaacson <adi@hexapodia.org>
Cc: Nai Xia <nai.xia@gmail.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
			
			
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					 3 changed files with 38 additions and 2 deletions
				
			
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			@ -177,6 +177,8 @@ struct lruvec {
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#define ISOLATE_CLEAN		((__force isolate_mode_t)0x4)
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/* Isolate unmapped file */
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#define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x8)
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/* Isolate for asynchronous migration */
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#define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x10)
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/* LRU Isolation modes. */
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typedef unsigned __bitwise__ isolate_mode_t;
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			@ -349,6 +349,9 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
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			continue;
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		}
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		if (!cc->sync)
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			mode |= ISOLATE_ASYNC_MIGRATE;
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		/* Try isolate the page */
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		if (__isolate_lru_page(page, mode, 0) != 0)
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			continue;
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										33
									
								
								mm/vmscan.c
									
									
									
									
									
								
							
							
						
						
									
										33
									
								
								mm/vmscan.c
									
									
									
									
									
								
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			@ -1075,9 +1075,40 @@ int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
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	ret = -EBUSY;
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	if ((mode & ISOLATE_CLEAN) && (PageDirty(page) || PageWriteback(page)))
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	/*
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	 * To minimise LRU disruption, the caller can indicate that it only
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	 * wants to isolate pages it will be able to operate on without
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	 * blocking - clean pages for the most part.
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	 *
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	 * ISOLATE_CLEAN means that only clean pages should be isolated. This
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	 * is used by reclaim when it is cannot write to backing storage
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	 *
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	 * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages
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	 * that it is possible to migrate without blocking
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	 */
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	if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) {
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		/* All the caller can do on PageWriteback is block */
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		if (PageWriteback(page))
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			return ret;
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		if (PageDirty(page)) {
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			struct address_space *mapping;
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			/* ISOLATE_CLEAN means only clean pages */
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			if (mode & ISOLATE_CLEAN)
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				return ret;
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			/*
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			 * Only pages without mappings or that have a
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			 * ->migratepage callback are possible to migrate
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			 * without blocking
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			 */
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			mapping = page_mapping(page);
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			if (mapping && !mapping->a_ops->migratepage)
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				return ret;
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		}
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	}
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	if ((mode & ISOLATE_UNMAPPED) && page_mapped(page))
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		return ret;
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