Commit 948c436e authored Feb 03, 2020 by David Hildenbrand Committed by Linus Torvalds Feb 04, 2020

mm/page_alloc: fix and rework pfn handling in memmap_init_zone()

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).

Link: http://lkml.kernel.org/r/20200113144035.10848-2-david@redhat.com


Fixes: a9a9e77f ("mm: move mirrored memory specific code outside of memmap_init_zone")
Signed-off-by: David Hildenbrand <david@redhat.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@suse.de>
Cc: "Jin, Zhi" <zhi.jin@intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 4b094b78

mm/page_alloc.c

+6 −3

Original line number	Diff line number	Diff line
		@@ -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++;
		}
		}

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