linux-kernel - [PATCH 1/2] mm/sparsemem: Defer the ms->section_mem

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Message-Id: <20180201071956.14365-2-bhe@redhat.com>
Date:   Thu,  1 Feb 2018 15:19:55 +0800
From:   Baoquan He <bhe@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        tglx@...utronix.de, douly.fnst@...fujitsu.com,
        Baoquan He <bhe@...hat.com>
Subject: [PATCH 1/2] mm/sparsemem: Defer the ms->section_mem_map clearing a little later

This will make sure number of sections marked as present won't be changed
in sparse_init(), so that for_each_present_section_nr() can iterate
each of them. This is preparation for later fix.

Signed-off-by: Baoquan He <bhe@...hat.com>
---
 mm/sparse-vmemmap.c |  1 -
 mm/sparse.c         | 15 ++++++++++++---
 2 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 17acf01791fa..315bea91e276 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -324,7 +324,6 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
 		ms = __nr_to_section(pnum);
 		pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
 		       __func__);
-		ms->section_mem_map = 0;
 	}
 
 	if (vmemmap_buf_start) {
diff --git a/mm/sparse.c b/mm/sparse.c
index 2609aba121e8..54eba92b72a1 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -478,7 +478,6 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
 		ms = __nr_to_section(pnum);
 		pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
 		       __func__);
-		ms->section_mem_map = 0;
 	}
 }
 #endif /* !CONFIG_SPARSEMEM_VMEMMAP */
@@ -610,17 +609,27 @@ void __init sparse_init(void)
 #endif
 
 	for_each_present_section_nr(0, pnum) {
+		struct mem_section *ms;
+		ms = __nr_to_section(pnum);
 		usemap = usemap_map[pnum];
-		if (!usemap)
+		if (!usemap) {
+#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
+			ms->section_mem_map = 0;
+#endif
 			continue;
+		}
 
 #ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
 		map = map_map[pnum];
 #else
 		map = sparse_early_mem_map_alloc(pnum);
 #endif
-		if (!map)
+		if (!map) {
+#ifdef CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
+			ms->section_mem_map = 0;
+#endif
 			continue;
+		}
 
 		sparse_init_one_section(__nr_to_section(pnum), pnum, map,
 								usemap);
-- 
2.13.6