linux-kernel - [patch] mm, migrate: increment fail count on ENOMEM

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Message-ID: <alpine.DEB.2.10.1605191510230.32658@chino.kir.corp.google.com>
Date:	Thu, 19 May 2016 15:11:23 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Vlastimil Babka <vbabka@...e.cz>,
	Mel Gorman <mgorman@...hsingularity.net>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [patch] mm, migrate: increment fail count on ENOMEM

If page migration fails due to -ENOMEM, nr_failed should still be
incremented for proper statistics.

This was encountered recently when all page migration vmstats showed 0,
and inferred that migrate_pages() was never called, although in reality
the first page migration failed because compaction_alloc() failed to find
a migration target.

This patch increments nr_failed so the vmstat is properly accounted on
ENOMEM.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 mm/migrate.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/migrate.c b/mm/migrate.c
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1171,6 +1171,7 @@ int migrate_pages(struct list_head *from, new_page_t get_new_page,

 			switch(rc) {
 			case -ENOMEM:
+				nr_failed++;
 				goto out;
 			case -EAGAIN:
 				retry++;