mm/memory_hotplug.c: drop unnecessary checks from register_mem_sect_under_node()

Callers of register_mem_sect_under_node() are always passing a valid
memory_block (not NULL), so we can safely drop the check for NULL.

In the same way, register_mem_sect_under_node() is only called in case
the node is online, so we can safely remove that check as well.

Link: http://lkml.kernel.org/r/20180622111839.10071-5-osalvador@techadventures.net
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Tested-by: Reza Arbab <arbab@linux.vnet.ibm.com>
Tested-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Pasha Tatashin <Pavel.Tatashin@microsoft.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/base/node.c

@@ -404,12 +404,7 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, void *arg)
 	int ret, nid = *(int *)arg;
 	unsigned long pfn, sect_start_pfn, sect_end_pfn;
 
-	if (!mem_blk)
-		return -EFAULT;
-
 	mem_blk->nid = nid;
-	if (!node_online(nid))
-		return 0;
 
 	sect_start_pfn = section_nr_to_pfn(mem_blk->start_section_nr);
 	sect_end_pfn = section_nr_to_pfn(mem_blk->end_section_nr);