memcg: fix init_page_cgroup nid with sparsemem

Commit 21a3c9646873 ("memcg: allocate memory cgroup structures in local
nodes") makes page_cgroup allocation as NUMA aware.  But that caused a
problem https://bugzilla.kernel.org/show_bug.cgi?id=36192.

The problem was getting a NID from invalid struct pages, which was not
initialized because it was out-of-node, out of [node_start_pfn,
node_end_pfn)

Now, with sparsemem, page_cgroup_init scans pfn from 0 to max_pfn.  But
this may scan a pfn which is not on any node and can access memmap which
is not initialized.

This makes page_cgroup_init() for SPARSEMEM node aware and remove a code
to get nid from page->flags.  (Then, we'll use valid NID always.)

[akpm@linux-foundation.org: try to fix up comments]
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 74ccff6..53bffc6 100644 (file)
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -162,13 +162,13 @@ static void free_page_cgroup(void *addr)
 }
 #endif
 
-static int __meminit init_section_page_cgroup(unsigned long pfn)
+static int __meminit init_section_page_cgroup(unsigned long pfn, int nid)
 {
        struct page_cgroup *base, *pc;
        struct mem_section *section;
        unsigned long table_size;
        unsigned long nr;
-       int nid, index;
+       int index;
 
        nr = pfn_to_section_nr(pfn);
        section = __nr_to_section(nr);
@@ -176,7 +176,6 @@ static int __meminit init_section_page_cgroup(unsigned long pfn)
        if (section->page_cgroup)
                return 0;
 
-       nid = page_to_nid(pfn_to_page(pfn));
        table_size = sizeof(struct page_cgroup) * PAGES_PER_SECTION;
        base = alloc_page_cgroup(table_size, nid);
 
@@ -196,7 +195,11 @@ static int __meminit init_section_page_cgroup(unsigned long pfn)
                pc = base + index;
                init_page_cgroup(pc, nr);
        }
-
+       /*
+        * The passed "pfn" may not be aligned to SECTION.  For the calculation
+        * we need to apply a mask.
+        */
+       pfn &= PAGE_SECTION_MASK;
        section->page_cgroup = base - pfn;
        total_usage += table_size;
        return 0;
@@ -225,10 +228,20 @@ int __meminit online_page_cgroup(unsigned long start_pfn,
        start = start_pfn & ~(PAGES_PER_SECTION - 1);
        end = ALIGN(start_pfn + nr_pages, PAGES_PER_SECTION);
 
+       if (nid == -1) {
+               /*
+                * In this case, "nid" already exists and contains valid memory.
+                * "start_pfn" passed to us is a pfn which is an arg for
+                * online__pages(), and start_pfn should exist.
+                */
+               nid = pfn_to_nid(start_pfn);
+               VM_BUG_ON(!node_state(nid, N_ONLINE));
+       }
+
        for (pfn = start; !fail && pfn < end; pfn += PAGES_PER_SECTION) {
                if (!pfn_present(pfn))
                        continue;
-               fail = init_section_page_cgroup(pfn);
+               fail = init_section_page_cgroup(pfn, nid);
        }
        if (!fail)
                return 0;
@@ -284,25 +297,47 @@ static int __meminit page_cgroup_callback(struct notifier_block *self,
 void __init page_cgroup_init(void)
 {
        unsigned long pfn;
-       int fail = 0;
+       int nid;
 
        if (mem_cgroup_disabled())
                return;
 
-       for (pfn = 0; !fail && pfn < max_pfn; pfn += PAGES_PER_SECTION) {
-               if (!pfn_present(pfn))
-                       continue;
-               fail = init_section_page_cgroup(pfn);
-       }
-       if (fail) {
-               printk(KERN_CRIT "try 'cgroup_disable=memory' boot option\n");
-               panic("Out of memory");
-       } else {
-               hotplug_memory_notifier(page_cgroup_callback, 0);
+       for_each_node_state(nid, N_HIGH_MEMORY) {
+               unsigned long start_pfn, end_pfn;
+
+               start_pfn = node_start_pfn(nid);
+               end_pfn = node_end_pfn(nid);
+               /*
+                * start_pfn and end_pfn may not be aligned to SECTION and the
+                * page->flags of out of node pages are not initialized.  So we
+                * scan [start_pfn, the biggest section's pfn < end_pfn) here.
+                */
+               for (pfn = start_pfn;
+                    pfn < end_pfn;
+                     pfn = ALIGN(pfn + 1, PAGES_PER_SECTION)) {
+
+                       if (!pfn_valid(pfn))
+                               continue;
+                       /*
+                        * Nodes's pfns can be overlapping.
+                        * We know some arch can have a nodes layout such as
+                        * -------------pfn-------------->
+                        * N0 | N1 | N2 | N0 | N1 | N2|....
+                        */
+                       if (pfn_to_nid(pfn) != nid)
+                               continue;
+                       if (init_section_page_cgroup(pfn, nid))
+                               goto oom;
+               }
        }
+       hotplug_memory_notifier(page_cgroup_callback, 0);
        printk(KERN_INFO "allocated %ld bytes of page_cgroup\n", total_usage);
-       printk(KERN_INFO "please try 'cgroup_disable=memory' option if you don't"
-       " want memory cgroups\n");
+       printk(KERN_INFO "please try 'cgroup_disable=memory' option if you "
+                        "don't want memory cgroups\n");
+       return;
+oom:
+       printk(KERN_CRIT "try 'cgroup_disable=memory' boot option\n");
+       panic("Out of memory");
 }
 
 void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat)