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Subject[PATCH v1 1/2] mm/page_alloc: fix and rework pfn handling in memmap_init_zone()
Date
Let's update the pfn manually whenever we continue the loop. This makes
the code easier to read but also less error prone (and we can directly
fix one issue).

When overlap_memmap_init() returns true, pfn is updated to
"memblock_region_memory_end_pfn(r)". So it already points at the *next*
pfn to process. Incrementing the pfn another time is wrong, we might
leave one uninitialized. I spotted this by inspecting the code, so I have
no idea if this is relevant in practise (with kernelcore=mirror).

Fixes: a9a9e77fbf27 ("mm: move mirrored memory specific code outside of memmap_init_zone")
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/page_alloc.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a41bd7341de1..a92791512077 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5905,18 +5905,20 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
}
#endif

- for (pfn = start_pfn; pfn < end_pfn; pfn++) {
+ for (pfn = start_pfn; pfn < end_pfn; ) {
/*
* There can be holes in boot-time mem_map[]s handed to this
* function. They do not exist on hotplugged memory.
*/
if (context == MEMMAP_EARLY) {
if (!early_pfn_valid(pfn)) {
- pfn = next_pfn(pfn) - 1;
+ pfn = next_pfn(pfn);
continue;
}
- if (!early_pfn_in_nid(pfn, nid))
+ if (!early_pfn_in_nid(pfn, nid)) {
+ pfn++;
continue;
+ }
if (overlap_memmap_init(zone, &pfn))
continue;
if (defer_init(nid, pfn, end_pfn))
@@ -5944,6 +5946,7 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
set_pageblock_migratetype(page, MIGRATE_MOVABLE);
cond_resched();
}
+ pfn++;
}
}

--
2.24.1
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