From 4c29700ed9908c15feeb84a40a415f4e921c5a66 Mon Sep 17 00:00:00 2001 From: Vincent Whitchurch Date: Sat, 30 Nov 2019 17:54:20 -0800 Subject: [PATCH] mm/sparse: consistently do not zero memmap sparsemem without VMEMMAP has two allocation paths to allocate the memory needed for its memmap (done in sparse_mem_map_populate()). In one allocation path (sparse_buffer_alloc() succeeds), the memory is not zeroed (since it was previously allocated with memblock_alloc_try_nid_raw()). In the other allocation path (sparse_buffer_alloc() fails and sparse_mem_map_populate() falls back to memblock_alloc_try_nid()), the memory is zeroed. AFAICS this difference does not appear to be on purpose. If the code is supposed to work with non-initialized memory (__init_single_page() takes care of zeroing the struct pages which are actually used), we should consistently not zero the memory, to avoid masking bugs. ( I noticed this because on my ARM64 platform, with 1 GiB of memory the first [and only] section is allocated from the zeroing path while with 2 GiB of memory the first 1 GiB section is allocated from the non-zeroing path. ) Michal: "the main user visible problem is a memory wastage. The overal amount of memory should be small. I wouldn't call it stable material." Link: http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@axis.com Signed-off-by: Vincent Whitchurch Acked-by: Michal Hocko Acked-by: David Hildenbrand Reviewed-by: Oscar Salvador Reviewed-by: Pavel Tatashin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/sparse.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/sparse.c b/mm/sparse.c index f6891c1..01e467a 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -458,7 +458,7 @@ struct page __init *__populate_section_memmap(unsigned long pfn, if (map) return map; - map = memblock_alloc_try_nid(size, + map = memblock_alloc_try_nid_raw(size, PAGE_SIZE, addr, MEMBLOCK_ALLOC_ACCESSIBLE, nid); if (!map) -- 2.7.4