The patch titled
Subject: mm/sparse: consistently do not zero memmap
has been added to the -mm tree. Its filename is
mm-sparse-consistently-do-not-zero-memmap.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-sparse-consistently-do-not-zero-memmap.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-sparse-consistently-do-not-zero-memmap.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Subject: 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.)
Link: http://lkml.kernel.org/r/20191030131122.8256-1-vincent.whitchurch@xxxxxxxx
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Oscar Salvador <osalvador@xxxxxxx>
Reviewed-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/sparse.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/sparse.c~mm-sparse-consistently-do-not-zero-memmap
+++ a/mm/sparse.c
@@ -458,7 +458,7 @@ struct page __init *__populate_section_m
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)
_
Patches currently in -mm which might be from vincent.whitchurch@xxxxxxxx are
mm-sparse-consistently-do-not-zero-memmap.patch
