mm/sparse.c: improve the error handling for sparse_add_one_section()

Improve the error handling for mm/sparse.c::sparse_add_one_section(). And I
see no reason to check 'usemap' until holding the 'pgdat_resize_lock'.

[[e-mail]: sparse_index_init() returns -EEXIST]
Cc: Christoph Lameter <[e-mail]>
Acked-by: Dave Hansen <[e-mail]>
Cc: Rik van Riel <[e-mail]>
Acked-by: Yasunori Goto <[e-mail]>
Cc: Andy Whitcroft <[e-mail]>
Signed-off-by: WANG Cong <[e-mail]>
Signed-off-by: Geoff Levand <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/sparse.c

···
 	 * no locking for this, because it does its own
 	 * plus, it does a kmalloc
 	 */
-	sparse_index_init(section_nr, pgdat->node_id);
+	ret = sparse_index_init(section_nr, pgdat->node_id);
+	if (ret < 0 && ret != -EEXIST)
+		return ret;
 	memmap = kmalloc_section_memmap(section_nr, pgdat->node_id, nr_pages);
+	if (!memmap)
+		return -ENOMEM;
 	usemap = __kmalloc_section_usemap();
+	if (!usemap) {
+		__kfree_section_memmap(memmap, nr_pages);
+		return -ENOMEM;
+	}
 
 	pgdat_resize_lock(pgdat, &flags);
 
···
 		goto out;
 	}
 
-	if (!usemap) {
-		ret = -ENOMEM;
-		goto out;
-	}
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 
 	ret = sparse_init_one_section(ms, section_nr, memmap, usemap);
 
 out:
 	pgdat_resize_unlock(pgdat, &flags);
-	if (ret <= 0)
+	if (ret <= 0) {
+		kfree(usemap);
 		__kfree_section_memmap(memmap, nr_pages);
+	}
 	return ret;
 }
 #endif