[PATCH] mm/sparse: Check section's existence earlier in sparse_add_one_section()

[Baoquan He]

No need to allocate usemap and memmap if section has been present.
And can clean up the handling on failure.

Signed-off-by: Baoquan He <bhe@xxxxxxxxxx>
---
 mm/sparse.c | 21 ++++++++-------------
 1 file changed, 8 insertions(+), 13 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 363f9d31b511..f564b531e0f7 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -714,7 +714,13 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 	ret = sparse_index_init(section_nr, nid);
 	if (ret < 0 && ret != -EEXIST)
 		return ret;
-	ret = 0;
+
+	ms = __pfn_to_section(start_pfn);
+	if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
+		ret = -EEXIST;
+		goto out;
+	}
+
 	memmap = kmalloc_section_memmap(section_nr, nid, altmap);
 	if (!memmap)
 		return -ENOMEM;
@@ -724,12 +730,6 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 		return -ENOMEM;
 	}
 
-	ms = __pfn_to_section(start_pfn);
-	if (ms->section_mem_map & SECTION_MARKED_PRESENT) {
-		ret = -EEXIST;
-		goto out;
-	}
-
 	/*
 	 * Poison uninitialized struct pages in order to catch invalid flags
 	 * combinations.
@@ -739,12 +739,7 @@ int __meminit sparse_add_one_section(int nid, unsigned long start_pfn,
 	section_mark_present(ms);
 	sparse_init_one_section(ms, section_nr, memmap, usemap);
 
-out:
-	if (ret < 0) {
-		kfree(usemap);
-		__kfree_section_memmap(memmap, altmap);
-	}
-	return ret;
+	return 0;
 }
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
-- 
2.17.2