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Shutemov" Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Jan 13, 2020 at 6:40 AM David Hildenbrand wrote: > > 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 > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Oscar Salvador > Cc: Kirill A. Shutemov > Signed-off-by: David Hildenbrand > --- > 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)) I'm pretty sure this is a bit broken. The overlap_memmap_init is going to return memblock_region_memory_end_pfn instead of the start of the next region. I think that is going to stick you in a mirrored region without advancing in that case. You would also need to have that case do a pfn++ before the continue; > @@ -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 > >