1 files changed, 120 insertions, 0 deletions
diff --git a/mm/percpu-km.c b/mm/percpu-km.c
new file mode 100644
index 000000000..35c994107
--- /dev/null
+++ b/mm/percpu-km.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * mm/percpu-km.c - kernel memory based chunk allocation
+ *
+ * Copyright (C) 2010		SUSE Linux Products GmbH
+ * Copyright (C) 2010		Tejun Heo <tj@kernel.org>
+ *
+ * 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.
+ */
+
+#if defined(CONFIG_SMP) && defined(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 page_start, int page_end, gfp_t gfp)
+{
+	return 0;
+}
+
+static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk,
+				  int page_start, int page_end)
+{
+	/* nada */
+}
+
+static struct pcpu_chunk *pcpu_create_chunk(enum pcpu_chunk_type type,
+					    gfp_t gfp)
+{
+	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
+	struct pcpu_chunk *chunk;
+	struct page *pages;
+	unsigned long flags;
+	int i;
+
+	chunk = pcpu_alloc_chunk(type, gfp);
+	if (!chunk)
+		return NULL;
+
+	pages = alloc_pages(gfp, 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);
+
+	spin_lock_irqsave(&pcpu_lock, flags);
+	pcpu_chunk_populated(chunk, 0, nr_pages);
+	spin_unlock_irqrestore(&pcpu_lock, flags);
+
+	pcpu_stats_chunk_alloc();
+	trace_percpu_create_chunk(chunk->base_addr);
+
+	return chunk;
+}
+
+static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
+{
+	const int nr_pages = pcpu_group_sizes[0] >> PAGE_SHIFT;
+
+	if (!chunk)
+		return;
+
+	pcpu_stats_chunk_dealloc();
+	trace_percpu_destroy_chunk(chunk->base_addr);
+
+	if (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) {
+		pr_crit("can't handle more than one group\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)
+		pr_warn("wasting %zu pages per chunk\n",
+			alloc_pages - nr_pages);
+
+	return 0;
+}