linux-kernel - [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable

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Date:   Thu,  3 Oct 2019 13:40:57 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     linux-mm@...ck.org
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Oscar Salvador <osalvador@...e.de>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Pavel Tatashin <pavel.tatashin@...rosoft.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] mm/page_alloc: Add a reason for reserved pages in has_unmovable_pages()

Having unmovable pages on a given pageblock should be reported correctly
when required with REPORT_FAILURE flag. But there can be a scenario where a
reserved page in the page block will get reported as a generic "unmovable"
reason code. Instead this should be changed to a more appropriate reason
code like "Reserved page".

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Vlastimil Babka <vbabka@...e.cz>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Mel Gorman <mgorman@...hsingularity.net>
Cc: Mike Rapoport <rppt@...ux.ibm.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Pavel Tatashin <pavel.tatashin@...rosoft.com>
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
---
 mm/page_alloc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 15c2050c629b..fbf93ea119d2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8206,8 +8206,10 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count,
 
 		page = pfn_to_page(check);
 
-		if (PageReserved(page))
+		if (PageReserved(page)) {
+			reason = "Reserved page";
 			goto unmovable;
+		}
 
 		/*
 		 * If the zone is movable and we have ruled out all reserved
-- 
2.20.1