x86,percpu: generalize lpage first chunk allocator

Generalize and move x86 setup_pcpu_lpage() into
pcpu_lpage_first_chunk().  setup_pcpu_lpage() now is a simple wrapper
around the generalized version.  Other than taking size parameters and
using arch supplied callbacks to allocate/free/map memory,
pcpu_lpage_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, factor out pcpu_calc_fc_sizes() which is common to
pcpu_embed_first_chunk() and pcpu_lpage_first_chunk().

[ Impact: code reorganization and generalization ]

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

1 files changed, 205 insertions, 4 deletions

diff --git a/mm/percpu.c b/mm/percpu.c
index f3fe7bc7378f..17db527ee2e2 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -1190,6 +1190,19 @@ size_t __init pcpu_setup_first_chunk(pcpu_get_page_fn_t get_page_fn,
         return pcpu_unit_size;
 }
 
+static size_t pcpu_calc_fc_sizes(size_t static_size, size_t reserved_size,
+                                 ssize_t *dyn_sizep)
+{
+        size_t size_sum;
+
+        size_sum = PFN_ALIGN(static_size + reserved_size +
+                             (*dyn_sizep >= 0 ? *dyn_sizep : 0));
+        if (*dyn_sizep != 0)
+                *dyn_sizep = size_sum - static_size - reserved_size;
+
+        return size_sum;
+}
+
 /*
  * Embedding first chunk setup helper.
  */
@@ -1241,10 +1254,7 @@ ssize_t __init pcpu_embed_first_chunk(size_t static_size, size_t reserved_size,
         unsigned int cpu;
 
         /* determine parameters and allocate */
-        pcpue_size = PFN_ALIGN(static_size + reserved_size +
-                               (dyn_size >= 0 ? dyn_size : 0));
-        if (dyn_size != 0)
-                dyn_size = pcpue_size - static_size - reserved_size;
+        pcpue_size = pcpu_calc_fc_sizes(static_size, reserved_size, &dyn_size);
 
         pcpue_unit_size = max_t(size_t, pcpue_size, PCPU_MIN_UNIT_SIZE);
         chunk_size = pcpue_unit_size * num_possible_cpus();
@@ -1391,6 +1401,197 @@ out_free_ar:
 }
 
 /*
+ * Large page remapping first chunk setup helper
+ */
+#ifdef CONFIG_NEED_MULTIPLE_NODES
+struct pcpul_ent {
+        unsigned int    cpu;
+        void            *ptr;
+};
+
+static size_t pcpul_size;
+static size_t pcpul_unit_size;
+static struct pcpul_ent *pcpul_map;
+static struct vm_struct pcpul_vm;
+
+static struct page * __init pcpul_get_page(unsigned int cpu, int pageno)
+{
+        size_t off = (size_t)pageno << PAGE_SHIFT;
+
+        if (off >= pcpul_size)
+                return NULL;
+
+        return virt_to_page(pcpul_map[cpu].ptr + off);
+}
+
+/**
+ * pcpu_lpage_first_chunk - remap the first percpu chunk using large page
+ * @static_size: the size of static percpu area in bytes
+ * @reserved_size: the size of reserved percpu area in bytes
+ * @dyn_size: free size for dynamic allocation in bytes, -1 for auto
+ * @lpage_size: the size of a large page
+ * @alloc_fn: function to allocate percpu lpage, always called with lpage_size
+ * @free_fn: function to free percpu memory, @size <= lpage_size
+ * @map_fn: function to map percpu lpage, always called with lpage_size
+ *
+ * This allocator uses large page as unit.  A large page is allocated
+ * for each cpu and each is remapped into vmalloc area using large
+ * page mapping.  As large page can be quite large, only part of it is
+ * used for the first chunk.  Unused part is returned to the bootmem
+ * allocator.
+ *
+ * So, the large pages are mapped twice - once to the physical mapping
+ * and to the vmalloc area for the first percpu chunk.  The double
+ * mapping does add one more large TLB entry pressure but still is
+ * much better than only using 4k mappings while still being NUMA
+ * friendly.
+ *
+ * RETURNS:
+ * The determined pcpu_unit_size which can be used to initialize
+ * percpu access on success, -errno on failure.
+ */
+ssize_t __init pcpu_lpage_first_chunk(size_t static_size, size_t reserved_size,
+                                      ssize_t dyn_size, size_t lpage_size,
+                                      pcpu_fc_alloc_fn_t alloc_fn,
+                                      pcpu_fc_free_fn_t free_fn,
+                                      pcpu_fc_map_fn_t map_fn)
+{
+        size_t size_sum;
+        size_t map_size;
+        unsigned int cpu;
+        int i, j;
+        ssize_t ret;
+
+        /*
+         * Currently supports only single page.  Supporting multiple
+         * pages won't be too difficult if it ever becomes necessary.
+         */
+        size_sum = pcpu_calc_fc_sizes(static_size, reserved_size, &dyn_size);
+
+        pcpul_unit_size = lpage_size;
+        pcpul_size = max_t(size_t, size_sum, PCPU_MIN_UNIT_SIZE);
+        if (pcpul_size > pcpul_unit_size) {
+                pr_warning("PERCPU: static data is larger than large page, "
+                           "can't use large page\n");
+                return -EINVAL;
+        }
+
+        /* allocate pointer array and alloc large pages */
+        map_size = PFN_ALIGN(num_possible_cpus() * sizeof(pcpul_map[0]));
+        pcpul_map = alloc_bootmem(map_size);
+
+        for_each_possible_cpu(cpu) {
+                void *ptr;
+
+                ptr = alloc_fn(cpu, lpage_size);
+                if (!ptr) {
+                        pr_warning("PERCPU: failed to allocate large page "
+                                   "for cpu%u\n", cpu);
+                        goto enomem;
+                }
+
+                /*
+                 * Only use pcpul_size bytes and give back the rest.
+                 *
+                 * Ingo: The lpage_size up-rounding bootmem is needed
+                 * to make sure the partial lpage is still fully RAM -
+                 * it's not well-specified to have a incompatible area
+                 * (unmapped RAM, device memory, etc.) in that hole.
+                 */
+                free_fn(ptr + pcpul_size, lpage_size - pcpul_size);
+
+                pcpul_map[cpu].cpu = cpu;
+                pcpul_map[cpu].ptr = ptr;
+
+                memcpy(ptr, __per_cpu_load, static_size);
+        }
+
+        /* allocate address and map */
+        pcpul_vm.flags = VM_ALLOC;
+        pcpul_vm.size = num_possible_cpus() * pcpul_unit_size;
+        vm_area_register_early(&pcpul_vm, pcpul_unit_size);
+
+        for_each_possible_cpu(cpu)
+                map_fn(pcpul_map[cpu].ptr, pcpul_unit_size,
+                       pcpul_vm.addr + cpu * pcpul_unit_size);
+
+        /* we're ready, commit */
+        pr_info("PERCPU: Remapped at %p with large pages, static data "
+                "%zu bytes\n", pcpul_vm.addr, static_size);
+
+        ret = pcpu_setup_first_chunk(pcpul_get_page, static_size,
+                                     reserved_size, dyn_size, pcpul_unit_size,
+                                     pcpul_vm.addr, NULL);
+
+        /* sort pcpul_map array for pcpu_lpage_remapped() */
+        for (i = 0; i < num_possible_cpus() - 1; i++)
+                for (j = i + 1; j < num_possible_cpus(); j++)
+                        if (pcpul_map[i].ptr > pcpul_map[j].ptr) {
+                                struct pcpul_ent tmp = pcpul_map[i];
+                                pcpul_map[i] = pcpul_map[j];
+                                pcpul_map[j] = tmp;
+                        }
+
+        return ret;
+
+enomem:
+        for_each_possible_cpu(cpu)
+                if (pcpul_map[cpu].ptr)
+                        free_fn(pcpul_map[cpu].ptr, pcpul_size);
+        free_bootmem(__pa(pcpul_map), map_size);
+        return -ENOMEM;
+}
+
+/**
+ * pcpu_lpage_remapped - determine whether a kaddr is in pcpul recycled area
+ * @kaddr: the kernel address in question
+ *
+ * Determine whether @kaddr falls in the pcpul recycled area.  This is
+ * used by pageattr to detect VM aliases and break up the pcpu large
+ * page mapping such that the same physical page is not mapped under
+ * different attributes.
+ *
+ * The recycled area is always at the tail of a partially used large
+ * page.
+ *
+ * RETURNS:
+ * Address of corresponding remapped pcpu address if match is found;
+ * otherwise, NULL.
+ */
+void *pcpu_lpage_remapped(void *kaddr)
+{
+        unsigned long unit_mask = pcpul_unit_size - 1;
+        void *lpage_addr = (void *)((unsigned long)kaddr & ~unit_mask);
+        unsigned long offset = (unsigned long)kaddr & unit_mask;
+        int left = 0, right = num_possible_cpus() - 1;
+        int pos;
+
+        /* pcpul in use at all? */
+        if (!pcpul_map)
+                return NULL;
+
+        /* okay, perform binary search */
+        while (left <= right) {
+                pos = (left + right) / 2;
+
+                if (pcpul_map[pos].ptr < lpage_addr)
+                        left = pos + 1;
+                else if (pcpul_map[pos].ptr > lpage_addr)
+                        right = pos - 1;
+                else {
+                        /* it shouldn't be in the area for the first chunk */
+                        WARN_ON(offset < pcpul_size);
+
+                        return pcpul_vm.addr +
+                                pcpul_map[pos].cpu * pcpul_unit_size + offset;
+                }
+        }
+
+        return NULL;
+}
+#endif
+
+/*
  * Generic percpu area setup.
  *
  * The embedding helper is used because its behavior closely resembles