linux-kernel - [PATCH] mm/page_alloc: fix memmap_init

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Date:   Thu,  1 Mar 2018 13:47:45 +0100
From:   Daniel Vacek <neelx@...hat.com>
To:     linux-kernel@...r.kernel.org, linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Paul Burton <paul.burton@...tec.com>,
        Daniel Vacek <neelx@...hat.com>, stable@...r.kernel.org
Subject: [PATCH] mm/page_alloc: fix memmap_init_zone pageblock alignment

In move_freepages() a BUG_ON() can be triggered on uninitialized page structures
due to pageblock alignment. Aligning the skipped pfns in memmap_init_zone() the
same way as in move_freepages_block() simply fixes those crashes.

Fixes: b92df1de5d28 ("[mm] page_alloc: skip over regions of invalid pfns where possible")
Signed-off-by: Daniel Vacek <neelx@...hat.com>
Cc: stable@...r.kernel.org
---
 mm/page_alloc.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cb416723538f..9edee36e6a74 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5359,9 +5359,14 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 			/*
 			 * Skip to the pfn preceding the next valid one (or
 			 * end_pfn), such that we hit a valid pfn (or end_pfn)
-			 * on our next iteration of the loop.
+			 * on our next iteration of the loop. Note that it needs
+			 * to be pageblock aligned even when the region itself
+			 * is not as move_freepages_block() can shift ahead of
+			 * the valid region but still depends on correct page
+			 * metadata.
 			 */
-			pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1;
+			pfn = (memblock_next_valid_pfn(pfn, end_pfn) &
+						~(pageblock_nr_pages-1)) - 1;
 #endif
 			continue;
 		}
-- 
2.16.2