The patch titled
Subject: mm/page_alloc: clear pages in alloc_contig_pages() with init_on_alloc=1 or __GFP_ZERO
has been added to the -mm tree. Its filename is
mm-page_alloc-clear-pages-in-alloc_contig_pages-with-init_on_alloc=1-or-__gfp_zero.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-clear-pages-in-alloc_contig_pages-with-init_on_alloc%3D1-or-__gfp_zero.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-clear-pages-in-alloc_contig_pages-with-init_on_alloc%3D1-or-__gfp_zero.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: David Hildenbrand <david@xxxxxxxxxx>
Subject: mm/page_alloc: clear pages in alloc_contig_pages() with init_on_alloc=1 or __GFP_ZERO
commit 6471384af2a6 ("mm: security: introduce init_on_alloc=1 and
init_on_free=1 boot options") resulted with init_on_alloc=1 in all pages
leaving the buddy via alloc_pages() and friends to be
initialized/cleared/zeroed on allocation.
However, the same logic is currently not applied to alloc_contig_pages():
allocated pages leaving the buddy aren't cleared with init_on_alloc=1 and
init_on_free=0. Let's also properly clear pages on that allocation path
and add support for __GFP_ZERO.
With this change, we will see double clearing of pages in some cases. One
example are gigantic pages (either allocated via CMA, or allocated
dynamically via alloc_contig_pages()) - which is the right thing to do
(and to be optimized outside of the buddy in the callers) as discussed in
https://lkml.kernel.org/r/20201019182853.7467-1-gpiccoli@xxxxxxxxxxxxx
This change implies that with init_on_alloc=1
- All CMA allocations will be cleared
- Gigantic pages allocated via alloc_contig_pages() will be cleared
- virtio-mem memory to be unplugged will be cleared. While this is
suboptimal, it's similar to memory balloon drivers handling, where
all pages to be inflated will get cleared as well.
Link: https://lkml.kernel.org/r/20201110193240.25401-1-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 24 +++++++++++++++++++++---
1 file changed, 21 insertions(+), 3 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-clear-pages-in-alloc_contig_pages-with-init_on_alloc=1-or-__gfp_zero
+++ a/mm/page_alloc.c
@@ -8449,6 +8449,19 @@ static int __alloc_contig_migrate_range(
return 0;
}
+static void __alloc_contig_clear_range(unsigned long start_pfn,
+ unsigned long end_pfn)
+{
+ unsigned long pfn;
+
+ for (pfn = start_pfn; pfn < end_pfn; pfn += MAX_ORDER_NR_PAGES) {
+ cond_resched();
+ kernel_init_free_pages(pfn_to_page(pfn),
+ min_t(unsigned long, end_pfn - pfn,
+ MAX_ORDER_NR_PAGES));
+ }
+}
+
/**
* alloc_contig_range() -- tries to allocate given range of pages
* @start: start PFN to allocate
@@ -8457,7 +8470,8 @@ static int __alloc_contig_migrate_range(
* #MIGRATE_MOVABLE or #MIGRATE_CMA). All pageblocks
* in range must have the same migratetype and it must
* be either of the two.
- * @gfp_mask: GFP mask to use during compaction
+ * @gfp_mask: GFP mask to use during compaction. __GFP_ZERO clears allocated
+ * pages.
*
* The PFN range does not have to be pageblock or MAX_ORDER_NR_PAGES
* aligned. The PFN range must belong to a single zone.
@@ -8484,7 +8498,7 @@ int alloc_contig_range(unsigned long sta
.mode = MIGRATE_SYNC,
.ignore_skip_hint = true,
.no_set_skip_hint = true,
- .gfp_mask = current_gfp_context(gfp_mask),
+ .gfp_mask = current_gfp_context(gfp_mask & ~__GFP_ZERO),
.alloc_contig = true,
};
INIT_LIST_HEAD(&cc.migratepages);
@@ -8596,6 +8610,9 @@ int alloc_contig_range(unsigned long sta
if (end != outer_end)
free_contig_range(end, outer_end - end);
+ if (!want_init_on_free() && want_init_on_alloc(gfp_mask))
+ __alloc_contig_clear_range(start, end);
+
done:
undo_isolate_page_range(pfn_max_align_down(start),
pfn_max_align_up(end), migratetype);
@@ -8649,7 +8666,8 @@ static bool zone_spans_last_pfn(const st
/**
* alloc_contig_pages() -- tries to find and allocate contiguous range of pages
* @nr_pages: Number of contiguous pages to allocate
- * @gfp_mask: GFP mask to limit search and used during compaction
+ * @gfp_mask: GFP mask to limit search and used during compaction. __GFP_ZERO
+ * clears allocated pages.
* @nid: Target node
* @nodemask: Mask for other possible nodes
*
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-page_alloc-clear-pages-in-alloc_contig_pages-with-init_on_alloc=1-or-__gfp_zero.patch
