mm/memory_hotplug: don't read nid from struct page during hotplug

During memory hotplugging the probe routine will leave struct pages
uninitialized, the same as it is currently done during boot.  Therefore,
we do not want to access the inside of struct pages before
__init_single_page() is called during onlining.

Because during hotplug we know that pages in one memory block belong to
the same numa node, we can skip the checking.  We should keep checking
for the boot case.

[pasha.tatashin@oracle.com: s/register_new_memory()/hotplug_memory_register()]
  Link: http://lkml.kernel.org/r/20180228030308.1116-6-pasha.tatashin@oracle.com
Link: http://lkml.kernel.org/r/20180215165920.8570-6-pasha.tatashin@oracle.com
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
Cc: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Steven Sistare <steven.sistare@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 15 insertions, 7 deletions

diff --git a/drivers/base/node.c b/drivers/base/node.c
index c5f81fc621ac..92b00a7e6a02 100644
--- a/drivers/base/node.c
+++ b/drivers/base/node.c
@@ -399,7 +399,8 @@ static int __ref get_nid_for_pfn(unsigned long pfn)
 }
 
 /* register memory section under specified node if it spans that node */
-int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
+int register_mem_sect_under_node(struct memory_block *mem_blk, int nid,
+                                 bool check_nid)
 {
         int ret;
         unsigned long pfn, sect_start_pfn, sect_end_pfn;
@@ -425,11 +426,18 @@ int register_mem_sect_under_node(struct memory_block *mem_blk, int nid)
                         continue;
                 }
 
-                page_nid = get_nid_for_pfn(pfn);
-                if (page_nid < 0)
-                        continue;
-                if (page_nid != nid)
-                        continue;
+                /*
+                 * We need to check if page belongs to nid only for the boot
+                 * case, during hotplug we know that all pages in the memory
+                 * block belong to the same node.
+                 */
+                if (check_nid) {
+                        page_nid = get_nid_for_pfn(pfn);
+                        if (page_nid < 0)
+                                continue;
+                        if (page_nid != nid)
+                                continue;
+                }
                 ret = sysfs_create_link_nowarn(&node_devices[nid]->dev.kobj,
                                         &mem_blk->dev.kobj,
                                         kobject_name(&mem_blk->dev.kobj));
@@ -504,7 +512,7 @@ int link_mem_sections(int nid, unsigned long start_pfn, unsigned long nr_pages)
 
                 mem_blk = find_memory_block_hinted(mem_sect, mem_blk);
 
-                ret = register_mem_sect_under_node(mem_blk, nid);
+                ret = register_mem_sect_under_node(mem_blk, nid, true);
                 if (!err)
                         err = ret;