From: David Hildenbrand <david@redhat.com>
To: Vincent Whitchurch <vincent.whitchurch@axis.com>,
akpm@linux-foundation.org
Cc: osalvador@suse.de, mhocko@suse.com, pasha.tatashin@oracle.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Vincent Whitchurch <rabinv@axis.com>
Subject: Re: [PATCH] mm/sparse: Consistently do not zero memmap
Date: Wed, 30 Oct 2019 14:31:48 +0100 [thread overview]
Message-ID: <eb5dbddd-afb6-2473-fa76-a4fabf62fb89@redhat.com> (raw)
In-Reply-To: <20191030131122.8256-1-vincent.whitchurch@axis.com>
On 30.10.19 14:11, Vincent Whitchurch wrote:
> 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 agree
Acked-by: David Hildenbrand <david@redhat.com>
>
> (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.)
>
> Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
> ---
> mm/sparse.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index f6891c1992b1..01e467adc219 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)
>
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2019-10-30 13:32 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-30 13:11 [PATCH] mm/sparse: Consistently do not zero memmap Vincent Whitchurch
2019-10-30 13:29 ` Michal Hocko
2019-10-30 14:02 ` Vincent Whitchurch
2019-10-30 14:12 ` Michal Hocko
2019-10-30 15:20 ` Pavel Tatashin
2019-10-30 15:31 ` Michal Hocko
2019-10-30 16:53 ` Pavel Tatashin
2019-10-30 17:31 ` Michal Hocko
2019-10-30 17:53 ` Pavel Tatashin
2019-10-30 18:01 ` Michal Hocko
2019-10-30 18:23 ` Pavel Tatashin
2019-10-31 7:25 ` Michal Hocko
2019-11-04 15:51 ` Vincent Whitchurch
2019-11-05 8:43 ` Michal Hocko
2019-11-15 23:55 ` Andrew Morton
2019-11-18 11:28 ` Michal Hocko
2019-10-30 13:31 ` David Hildenbrand [this message]
2019-10-30 13:38 ` Oscar Salvador
2019-10-30 15:21 ` Pavel Tatashin
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