1 files changed, 77 insertions, 1 deletions

diff --git a/mm/sparse.c b/mm/sparse.c
index 7a3650923d9a..8ffc08990008 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -269,16 +269,92 @@ static unsigned long *__kmalloc_section_usemap(void)
 }
 #endif /* CONFIG_MEMORY_HOTPLUG */
 
+#ifdef CONFIG_MEMORY_HOTREMOVE
+static unsigned long * __init
+sparse_early_usemap_alloc_pgdat_section(struct pglist_data *pgdat)
+{
+        unsigned long section_nr;
+
+        /*
+         * A page may contain usemaps for other sections preventing the
+         * page being freed and making a section unremovable while
+         * other sections referencing the usemap retmain active. Similarly,
+         * a pgdat can prevent a section being removed. If section A
+         * contains a pgdat and section B contains the usemap, both
+         * sections become inter-dependent. This allocates usemaps
+         * from the same section as the pgdat where possible to avoid
+         * this problem.
+         */
+        section_nr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
+        return alloc_bootmem_section(usemap_size(), section_nr);
+}
+
+static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
+{
+        unsigned long usemap_snr, pgdat_snr;
+        static unsigned long old_usemap_snr = NR_MEM_SECTIONS;
+        static unsigned long old_pgdat_snr = NR_MEM_SECTIONS;
+        struct pglist_data *pgdat = NODE_DATA(nid);
+        int usemap_nid;
+
+        usemap_snr = pfn_to_section_nr(__pa(usemap) >> PAGE_SHIFT);
+        pgdat_snr = pfn_to_section_nr(__pa(pgdat) >> PAGE_SHIFT);
+        if (usemap_snr == pgdat_snr)
+                return;
+
+        if (old_usemap_snr == usemap_snr && old_pgdat_snr == pgdat_snr)
+                /* skip redundant message */
+                return;
+
+        old_usemap_snr = usemap_snr;
+        old_pgdat_snr = pgdat_snr;
+
+        usemap_nid = sparse_early_nid(__nr_to_section(usemap_snr));
+        if (usemap_nid != nid) {
+                printk(KERN_INFO
+                       "node %d must be removed before remove section %ld\n",
+                       nid, usemap_snr);
+                return;
+        }
+        /*
+         * There is a circular dependency.
+         * Some platforms allow un-removable section because they will just
+         * gather other removable sections for dynamic partitioning.
+         * Just notify un-removable section's number here.
+         */
+        printk(KERN_INFO "Section %ld and %ld (node %d)", usemap_snr,
+               pgdat_snr, nid);
+        printk(KERN_CONT
+               " have a circular dependency on usemap and pgdat allocations\n");
+}
+#else
+static unsigned long * __init
+sparse_early_usemap_alloc_pgdat_section(struct pglist_data *pgdat)
+{
+        return NULL;
+}
+
+static void __init check_usemap_section_nr(int nid, unsigned long *usemap)
+{
+}
+#endif /* CONFIG_MEMORY_HOTREMOVE */
+
 static unsigned long *__init sparse_early_usemap_alloc(unsigned long pnum)
 {
         unsigned long *usemap;
         struct mem_section *ms = __nr_to_section(pnum);
         int nid = sparse_early_nid(ms);
 
-        usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
+        usemap = sparse_early_usemap_alloc_pgdat_section(NODE_DATA(nid));
         if (usemap)
                 return usemap;
 
+        usemap = alloc_bootmem_node(NODE_DATA(nid), usemap_size());
+        if (usemap) {
+                check_usemap_section_nr(nid, usemap);
+                return usemap;
+        }
+
         /* Stupid: suppress gcc warning for SPARSEMEM && !NUMA */
         nid = 0;