2 files changed, 108 insertions, 0 deletions

diff --git a/mm/percpu-km.c b/mm/percpu-km.c
new file mode 100644
index 000000000000..df680855540a
--- /dev/null
+++ b/mm/percpu-km.c
@@ -0,0 +1,104 @@
+/*
+ * mm/percpu-km.c - kernel memory based chunk allocation
+ *
+ * Copyright (C) 2010           SUSE Linux Products GmbH
+ * Copyright (C) 2010           Tejun Heo <tj@kernel.org>
+ *
+ * This file is released under the GPLv2.
+ *
+ * Chunks are allocated as a contiguous kernel memory using gfp
+ * allocation.  This is to be used on nommu architectures.
+ *
+ * To use percpu-km,
+ *
+ * - define CONFIG_NEED_PER_CPU_KM from the arch Kconfig.
+ *
+ * - CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK must not be defined.  It's
+ *   not compatible with PER_CPU_KM.  EMBED_FIRST_CHUNK should work
+ *   fine.
+ *
+ * - NUMA is not supported.  When setting up the first chunk,
+ *   @cpu_distance_fn should be NULL or report all CPUs to be nearer
+ *   than or at LOCAL_DISTANCE.
+ *
+ * - It's best if the chunk size is power of two multiple of
+ *   PAGE_SIZE.  Because each chunk is allocated as a contiguous
+ *   kernel memory block using alloc_pages(), memory will be wasted if
+ *   chunk size is not aligned.  percpu-km code will whine about it.
+ */
+
+#ifdef CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK
+#error "contiguous percpu allocation is incompatible with paged first chunk"
+#endif
+
+#include <linux/log2.h>
+
+static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
+{
+        /* noop */
+        return 0;
+}
+
+static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
+{
+        /* nada */
+}
+
+static struct pcpu_chunk *pcpu_create_chunk(void)
+{
+        const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
+        struct pcpu_chunk *chunk;
+        struct page *pages;
+        int i;
+
+        chunk = pcpu_alloc_chunk();
+        if (!chunk)
+                return NULL;
+
+        pages = alloc_pages(GFP_KERNEL, order_base_2(nr_pages));
+        if (!pages) {
+                pcpu_free_chunk(chunk);
+                return NULL;
+        }
+
+        for (i = 0; i < nr_pages; i++)
+                pcpu_set_page_chunk(nth_page(pages, i), chunk);
+
+        chunk->data = pages;
+        chunk->base_addr = page_address(pages) - pcpu_group_offsets[0];
+        return chunk;
+}
+
+static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
+{
+        const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
+
+        if (chunk && chunk->data)
+                __free_pages(chunk->data, order_base_2(nr_pages));
+        pcpu_free_chunk(chunk);
+}
+
+static struct page *pcpu_addr_to_page(void *addr)
+{
+        return virt_to_page(addr);
+}
+
+static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
+{
+        size_t nr_pages, alloc_pages;
+
+        /* all units must be in a single group */
+        if (ai->nr_groups != 1) {
+                printk(KERN_CRIT "percpu: can't handle more than one groups\n");
+                return -EINVAL;
+        }
+
+        nr_pages = (ai->groups[0].nr_units * ai->unit_size) >> PAGE_SHIFT;
+        alloc_pages = roundup_pow_of_two(nr_pages);
+
+        if (alloc_pages > nr_pages)
+                printk(KERN_WARNING "percpu: wasting %zu pages per chunk\n",
+                       alloc_pages - nr_pages);
+
+        return 0;
+}
diff --git a/mm/percpu.c b/mm/percpu.c
index 15f680430671..39f7dfd59585 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -654,7 +654,11 @@ static void pcpu_destroy_chunk(struct pcpu_chunk *chunk);
 static struct page *pcpu_addr_to_page(void *addr);
 static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai);
 
+#ifdef CONFIG_NEED_PER_CPU_KM
+#include "percpu-km.c"
+#else
 #include "percpu-vm.c"
+#endif
 
 /**
  * pcpu_chunk_addr_search - determine chunk containing specified address