linux-kernel - [v5 08/15] mm: zero struct pages during initialization

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Date:   Thu,  3 Aug 2017 17:23:46 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     linux-kernel@...r.kernel.org, sparclinux@...r.kernel.org,
        linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        x86@...nel.org, kasan-dev@...glegroups.com, borntraeger@...ibm.com,
        heiko.carstens@...ibm.com, davem@...emloft.net,
        willy@...radead.org, mhocko@...nel.org
Subject: [v5 08/15] mm: zero struct pages during initialization

Add struct page zeroing as a part of initialization of other fields in
__init_single_page().

Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
Reviewed-by: Steven Sistare <steven.sistare@...cle.com>
Reviewed-by: Daniel Jordan <daniel.m.jordan@...cle.com>
Reviewed-by: Bob Picco <bob.picco@...cle.com>
---
 include/linux/mm.h | 9 +++++++++
 mm/page_alloc.c    | 1 +
 2 files changed, 10 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 46b9ac5e8569..183ac5e733db 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -94,6 +94,15 @@ extern int mmap_rnd_compat_bits __read_mostly;
 #endif
 
 /*
+ * On some architectures it is expensive to call memset() for small sizes.
+ * Those architectures should provide their own implementation of "struct page"
+ * zeroing by defining this macro in <asm/pgtable.h>.
+ */
+#ifndef mm_zero_struct_page
+#define mm_zero_struct_page(pp)  ((void)memset((pp), 0, sizeof(struct page)))
+#endif
+
+/*
  * Default maximum number of active map areas, this limits the number of vmas
  * per mm struct. Users can overwrite this number by sysctl but there is a
  * problem.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 05110ae50aca..cbcdd53ad9f8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1168,6 +1168,7 @@ static void free_one_page(struct zone *zone,
 static void __meminit __init_single_page(struct page *page, unsigned long pfn,
 				unsigned long zone, int nid)
 {
+	mm_zero_struct_page(page);
 	set_page_links(page, zone, nid, pfn);
 	init_page_count(page);
 	page_mapcount_reset(page);
-- 
2.13.4