x86,percpu: generalize 4k first chunk allocator

Generalize and move x86 setup_pcpu_4k() into pcpu_4k_first_chunk().
setup_pcpu_4k() now is a simple wrapper around the generalized
version.  Other than taking size parameters and using arch supplied
callbacks to allocate/free memory, pcpu_4k_first_chunk() is identical
to the original implementation.

This simplifies arch code and will help converting more archs to
dynamic percpu allocator.

While at it, s/pcpu_populate_pte_fn_t/pcpu_fc_populate_pte_fn_t/ for
consistency.

[ Impact: code reorganization and generalization ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>

1 files changed, 84 insertions, 1 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index fc6babe6e554..27b0f40a3ea8 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1037,7 +1037,7 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
                                      size_t static_size, size_t reserved_size,
                                      ssize_t dyn_size, ssize_t unit_size,
                                      void *base_addr,
-                                     pcpu_populate_pte_fn_t populate_pte_fn)
+                                     pcpu_fc_populate_pte_fn_t populate_pte_fn)
 {
         static struct vm_struct first_vm;
         static int smap[2], dmap[2];
@@ -1271,6 +1271,89 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
 }
 
 /*
+ * 4k page first chunk setup helper.
+ */
+static struct page **pcpu4k_pages __initdata;
+static int pcpu4k_nr_static_pages __initdata;
+
+static struct page * __init pcpu4k_get_page(unsigned int cpu, int pageno)
+{
+        if (pageno < pcpu4k_nr_static_pages)
+                return pcpu4k_pages[cpu * pcpu4k_nr_static_pages + pageno];
+        return NULL;
+}
+
+/**
+ * pcpu_4k_first_chunk - map the first chunk using PAGE_SIZE pages
+ * @static_size: the size of static percpu area in bytes
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @alloc_fn: function to allocate percpu page, always called with PAGE_SIZE
+ * @free_fn: funtion to free percpu page, always called with PAGE_SIZE
+ * @populate_pte_fn: function to populate pte
+ *
+ * This is a helper to ease setting up embedded first percpu chunk and
+ * can be called where pcpu_setup_first_chunk() is expected.
+ *
+ * This is the basic allocator.  Static percpu area is allocated
+ * page-by-page into vmalloc area.
+ *
+ * RETURNS:
+ * The determined pcpu_unit_size which can be used to initialize
+ * percpu access on success, -errno on failure.
+ */
+ssize_t __init pcpu_4k_first_chunk(size_t static_size, size_t reserved_size,
+                                   pcpu_fc_alloc_fn_t alloc_fn,
+                                   pcpu_fc_free_fn_t free_fn,
+                                   pcpu_fc_populate_pte_fn_t populate_pte_fn)
+{
+        size_t pages_size;
+        unsigned int cpu;
+        int i, j;
+        ssize_t ret;
+
+        pcpu4k_nr_static_pages = PFN_UP(static_size);
+
+        /* unaligned allocations can't be freed, round up to page size */
+        pages_size = PFN_ALIGN(pcpu4k_nr_static_pages * num_possible_cpus() *
+                               sizeof(pcpu4k_pages[0]));
+        pcpu4k_pages = alloc_bootmem(pages_size);
+
+        /* allocate and copy */
+        j = 0;
+        for_each_possible_cpu(cpu)
+                for (i = 0; i < pcpu4k_nr_static_pages; i++) {
+                        void *ptr;
+
+                        ptr = alloc_fn(cpu, PAGE_SIZE);
+                        if (!ptr) {
+                                pr_warning("PERCPU: failed to allocate "
+                                           "4k page for cpu%u\n", cpu);
+                                goto enomem;
+                        }
+
+                        memcpy(ptr, __per_cpu_load + i * PAGE_SIZE, PAGE_SIZE);
+                        pcpu4k_pages[j++] = virt_to_page(ptr);
+                }
+
+        /* we're ready, commit */
+        pr_info("PERCPU: Allocated %d 4k pages, static data %zu bytes\n",
+                pcpu4k_nr_static_pages, static_size);
+
+        ret = pcpu_setup_first_chunk(pcpu4k_get_page, static_size,
+                                     reserved_size, -1,
+                                     -1, NULL, populate_pte_fn);
+        goto out_free_ar;
+
+enomem:
+        while (--j >= 0)
+                free_fn(page_address(pcpu4k_pages[j]), PAGE_SIZE);
+        ret = -ENOMEM;
+out_free_ar:
+        free_bootmem(__pa(pcpu4k_pages), pages_size);
+        return ret;
+}
+
+/*
  * Generic percpu area setup.
  *
  * The embedding helper is used because its behavior closely resembles