linux-kernel - [PATCH] mm, memory_hotplug: __offline

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Message-Id: <20190115120307.22768-1-mhocko@kernel.org>
Date:   Tue, 15 Jan 2019 13:03:07 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Jan Kara <jack@...e.cz>, Oscar Salvador <OSalvador@...e.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH] mm, memory_hotplug: __offline_pages fix wrong locking

From: Michal Hocko <mhocko@...e.com>

Jan has noticed that we do double unlock on some failure paths when
offlining a page range. This is indeed the case when test_pages_in_a_zone
respp. start_isolate_page_range fail. This was an omission when forward
porting the debugging patch from an older kernel.

Fix the issue by dropping mem_hotplug_done from the failure condition
and keeping the single unlock in the catch all failure path.

Reported-by: Jan Kara <jack@...e.cz>
Fixes: 7960509329c2 ("mm, memory_hotplug: print reason for the offlining failure")
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 mm/memory_hotplug.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index b9a667d36c55..faeeaccc5fae 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1576,7 +1576,6 @@ static int __ref __offline_pages(unsigned long start_pfn,
 	   we assume this for now. .*/
 	if (!test_pages_in_a_zone(start_pfn, end_pfn, &valid_start,
 				  &valid_end)) {
-		mem_hotplug_done();
 		ret = -EINVAL;
 		reason = "multizone range";
 		goto failed_removal;
@@ -1591,7 +1590,6 @@ static int __ref __offline_pages(unsigned long start_pfn,
 				       MIGRATE_MOVABLE,
 				       SKIP_HWPOISON | REPORT_FAILURE);
 	if (ret) {
-		mem_hotplug_done();
 		reason = "failure to isolate range";
 		goto failed_removal;
 	}
-- 
2.20.1