linux-kernel - [PATCH] mm, compaction: Round-robin the order while searching the free lists for a target -fix

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Date:   Wed, 9 Jan 2019 11:16:09 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Vlastimil Babka <vbabka@...e.cz>, ying.huang@...el.com,
        Dan Carpenter <dan.carpenter@...cle.com>, kirill@...temov.name,
        Linux-MM <linux-mm@...ck.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>
Subject: [PATCH] mm, compaction: Round-robin the order while searching the
 free lists for a target -fix

Dan Carpenter reported the following static checker warning:

        mm/compaction.c:1252 next_search_order()
        warn: impossible condition '(cc->search_order < 0) => (0-u16max < 0)'

While a negative order never makes sense, the control flow is
easier if search_order is signed. This is a fix to the mmotm patch
broken-out/mm-compaction-round-robin-the-order-while-searching-the-free-lists-for-a-target.patch

Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
---
 mm/internal.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/internal.h b/mm/internal.h
index d028abd8a8f3..e74dbc257550 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -192,7 +192,7 @@ struct compact_control {
 	unsigned long total_migrate_scanned;
 	unsigned long total_free_scanned;
 	unsigned short fast_search_fail;/* failures to use free list searches */
-	unsigned short search_order;	/* order to start a fast search at */
+	short search_order;		/* order to start a fast search at */
 	const gfp_t gfp_mask;		/* gfp mask of a direct compactor */
 	int order;			/* order a direct compactor needs */
 	int migratetype;		/* migratetype of direct compactor */