linux-kernel - [PATCH] mm: don't do zero_resv_unavail if memmap is not allocated

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Message-Id: <20180716151630.770-1-pasha.tatashin@oracle.com>
Date:   Mon, 16 Jul 2018 11:16:30 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        linux-mm@...ck.org, mgorman@...hsingularity.net,
        pasha.tatashin@...cle.com, torvalds@...ux-foundation.org,
        gregkh@...uxfoundation.org
Subject: [PATCH] mm: don't do zero_resv_unavail if memmap is not allocated

Moving zero_resv_unavail before memmap_init_zone(), caused a regression on
x86-32.

The cause is that we access struct pages before they are allocated when
CONFIG_FLAT_NODE_MEM_MAP is used.

free_area_init_nodes()
  zero_resv_unavail()
    mm_zero_struct_page(pfn_to_page(pfn)); <- struct page is not alloced
  free_area_init_node()
    if CONFIG_FLAT_NODE_MEM_MAP
      alloc_node_mem_map()
        memblock_virt_alloc_node_nopanic() <- struct page alloced here

On the other hand memblock_virt_alloc_node_nopanic() zeroes all the memory
that it returns, so we do not need to do zero_resv_unavail() here.

Fixes: e181ae0c5db9 ("mm: zero unavailable pages before memmap init")
Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>
---
 include/linux/mm.h | 2 +-
 mm/page_alloc.c    | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a0fbb9ffe380..3982c83fdcbf 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2132,7 +2132,7 @@ extern int __meminit __early_pfn_to_nid(unsigned long pfn,
 					struct mminit_pfnnid_cache *state);
 #endif
 
-#ifdef CONFIG_HAVE_MEMBLOCK
+#if defined(CONFIG_HAVE_MEMBLOCK) && !defined(CONFIG_FLAT_NODE_MEM_MAP)
 void zero_resv_unavail(void);
 #else
 static inline void zero_resv_unavail(void) {}
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5d800d61ddb7..a790ef4be74e 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6383,7 +6383,7 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
 	free_area_init_core(pgdat);
 }
 
-#ifdef CONFIG_HAVE_MEMBLOCK
+#if defined(CONFIG_HAVE_MEMBLOCK) && !defined(CONFIG_FLAT_NODE_MEM_MAP)
 /*
  * Only struct pages that are backed by physical memory are zeroed and
  * initialized by going through __init_single_page(). But, there are some
@@ -6421,7 +6421,7 @@ void __paginginit zero_resv_unavail(void)
 	if (pgcnt)
 		pr_info("Reserved but unavailable: %lld pages", pgcnt);
 }
-#endif /* CONFIG_HAVE_MEMBLOCK */
+#endif /* CONFIG_HAVE_MEMBLOCK && !CONFIG_FLAT_NODE_MEM_MAP */
 
 #ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
 
-- 
2.18.0