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-rw-r--r--mm/percpu-km.c130
1 files changed, 130 insertions, 0 deletions
diff --git a/mm/percpu-km.c b/mm/percpu-km.c
new file mode 100644
index 000000000..fe31aa19d
--- /dev/null
+++ b/mm/percpu-km.c
@@ -0,0 +1,130 @@
+// 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 void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
+ int page_start, int page_end)
+{
+ /* nothing */
+}
+
+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(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(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;
+}
+
+static bool pcpu_should_reclaim_chunk(struct pcpu_chunk *chunk)
+{
+ return false;
+}