percpu-vm.c

Go to the documentation of this file.

/*
 * mm/percpu-vm.c - vmalloc area based chunk allocation
 *
 * Copyright (C) 2010       SUSE Linux Products GmbH
 * Copyright (C) 2010       Tejun Heo <[email protected]>
 *
 * This file is released under the GPLv2.
 *
 * Chunks are mapped into vmalloc areas and populated page by page.
 * This is the default chunk allocator.
 */

static struct page *pcpu_chunk_page(struct pcpu_chunk *chunk,
                    unsigned int cpu, int page_idx)
{
    /* must not be used on pre-mapped chunk */
    WARN_ON(chunk->immutable);

    return vmalloc_to_page((void *)pcpu_chunk_addr(chunk, cpu, page_idx));
}

static struct page **pcpu_get_pages_and_bitmap(struct pcpu_chunk *chunk,
                           unsigned long **bitmapp,
                           bool may_alloc)
{
    static struct page **pages;
    static unsigned long *bitmap;
    size_t pages_size = pcpu_nr_units * pcpu_unit_pages * sizeof(pages[0]);
    size_t bitmap_size = BITS_TO_LONGS(pcpu_unit_pages) *
                 sizeof(unsigned long);

    if (!pages || !bitmap) {
        if (may_alloc && !pages)
            pages = pcpu_mem_zalloc(pages_size);
        if (may_alloc && !bitmap)
            bitmap = pcpu_mem_zalloc(bitmap_size);
        if (!pages || !bitmap)
            return NULL;
    }

    bitmap_copy(bitmap, chunk->populated, pcpu_unit_pages);

    *bitmapp = bitmap;
    return pages;
}

static void pcpu_free_pages(struct pcpu_chunk *chunk,
                struct page **pages, unsigned long *populated,
                int page_start, int page_end)
{
    unsigned int cpu;
    int i;

    for_each_possible_cpu(cpu) {
        for (i = page_start; i < page_end; i++) {
            struct page *page = pages[pcpu_page_idx(cpu, i)];

            if (page)
                __free_page(page);
        }
    }
}

static int pcpu_alloc_pages(struct pcpu_chunk *chunk,
                struct page **pages, unsigned long *populated,
                int page_start, int page_end)
{
    const gfp_t gfp = GFP_KERNEL | __GFP_HIGHMEM | __GFP_COLD;
    unsigned int cpu;
    int i;

    for_each_possible_cpu(cpu) {
        for (i = page_start; i < page_end; i++) {
            struct page **pagep = &pages[pcpu_page_idx(cpu, i)];

            *pagep = alloc_pages_node(cpu_to_node(cpu), gfp, 0);
            if (!*pagep) {
                pcpu_free_pages(chunk, pages, populated,
                        page_start, page_end);
                return -ENOMEM;
            }
        }
    }
    return 0;
}

static void pcpu_pre_unmap_flush(struct pcpu_chunk *chunk,
                 int page_start, int page_end)
{
    flush_cache_vunmap(
        pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
        pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
}

static void __pcpu_unmap_pages(unsigned long addr, int nr_pages)
{
    unmap_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT);
}

static void pcpu_unmap_pages(struct pcpu_chunk *chunk,
                 struct page **pages, unsigned long *populated,
                 int page_start, int page_end)
{
    unsigned int cpu;
    int i;

    for_each_possible_cpu(cpu) {
        for (i = page_start; i < page_end; i++) {
            struct page *page;

            page = pcpu_chunk_page(chunk, cpu, i);
            WARN_ON(!page);
            pages[pcpu_page_idx(cpu, i)] = page;
        }
        __pcpu_unmap_pages(pcpu_chunk_addr(chunk, cpu, page_start),
                   page_end - page_start);
    }

    bitmap_clear(populated, page_start, page_end - page_start);
}

static void pcpu_post_unmap_tlb_flush(struct pcpu_chunk *chunk,
                      int page_start, int page_end)
{
    flush_tlb_kernel_range(
        pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
        pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
}

static int __pcpu_map_pages(unsigned long addr, struct page **pages,
                int nr_pages)
{
    return map_kernel_range_noflush(addr, nr_pages << PAGE_SHIFT,
                    PAGE_KERNEL, pages);
}

static int pcpu_map_pages(struct pcpu_chunk *chunk,
              struct page **pages, unsigned long *populated,
              int page_start, int page_end)
{
    unsigned int cpu, tcpu;
    int i, err;

    for_each_possible_cpu(cpu) {
        err = __pcpu_map_pages(pcpu_chunk_addr(chunk, cpu, page_start),
                       &pages[pcpu_page_idx(cpu, page_start)],
                       page_end - page_start);
        if (err < 0)
            goto err;
    }

    /* mapping successful, link chunk and mark populated */
    for (i = page_start; i < page_end; i++) {
        for_each_possible_cpu(cpu)
            pcpu_set_page_chunk(pages[pcpu_page_idx(cpu, i)],
                        chunk);
        __set_bit(i, populated);
    }

    return 0;

err:
    for_each_possible_cpu(tcpu) {
        if (tcpu == cpu)
            break;
        __pcpu_unmap_pages(pcpu_chunk_addr(chunk, tcpu, page_start),
                   page_end - page_start);
    }
    return err;
}

static void pcpu_post_map_flush(struct pcpu_chunk *chunk,
                int page_start, int page_end)
{
    flush_cache_vmap(
        pcpu_chunk_addr(chunk, pcpu_low_unit_cpu, page_start),
        pcpu_chunk_addr(chunk, pcpu_high_unit_cpu, page_end));
}

static int pcpu_populate_chunk(struct pcpu_chunk *chunk, int off, int size)
{
    int page_start = PFN_DOWN(off);
    int page_end = PFN_UP(off + size);
    int free_end = page_start, unmap_end = page_start;
    struct page **pages;
    unsigned long *populated;
    unsigned int cpu;
    int rs, re, rc;

    /* quick path, check whether all pages are already there */
    rs = page_start;
    pcpu_next_pop(chunk, &rs, &re, page_end);
    if (rs == page_start && re == page_end)
        goto clear;

    /* need to allocate and map pages, this chunk can't be immutable */
    WARN_ON(chunk->immutable);

    pages = pcpu_get_pages_and_bitmap(chunk, &populated, true);
    if (!pages)
        return -ENOMEM;

    /* alloc and map */
    pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
        rc = pcpu_alloc_pages(chunk, pages, populated, rs, re);
        if (rc)
            goto err_free;
        free_end = re;
    }

    pcpu_for_each_unpop_region(chunk, rs, re, page_start, page_end) {
        rc = pcpu_map_pages(chunk, pages, populated, rs, re);
        if (rc)
            goto err_unmap;
        unmap_end = re;
    }
    pcpu_post_map_flush(chunk, page_start, page_end);

    /* commit new bitmap */
    bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
clear:
    for_each_possible_cpu(cpu)
        memset((void *)pcpu_chunk_addr(chunk, cpu, 0) + off, 0, size);
    return 0;

err_unmap:
    pcpu_pre_unmap_flush(chunk, page_start, unmap_end);
    pcpu_for_each_unpop_region(chunk, rs, re, page_start, unmap_end)
        pcpu_unmap_pages(chunk, pages, populated, rs, re);
    pcpu_post_unmap_tlb_flush(chunk, page_start, unmap_end);
err_free:
    pcpu_for_each_unpop_region(chunk, rs, re, page_start, free_end)
        pcpu_free_pages(chunk, pages, populated, rs, re);
    return rc;
}

static void pcpu_depopulate_chunk(struct pcpu_chunk *chunk, int off, int size)
{
    int page_start = PFN_DOWN(off);
    int page_end = PFN_UP(off + size);
    struct page **pages;
    unsigned long *populated;
    int rs, re;

    /* quick path, check whether it's empty already */
    rs = page_start;
    pcpu_next_unpop(chunk, &rs, &re, page_end);
    if (rs == page_start && re == page_end)
        return;

    /* immutable chunks can't be depopulated */
    WARN_ON(chunk->immutable);

    /*
     * If control reaches here, there must have been at least one
     * successful population attempt so the temp pages array must
     * be available now.
     */
    pages = pcpu_get_pages_and_bitmap(chunk, &populated, false);
    BUG_ON(!pages);

    /* unmap and free */
    pcpu_pre_unmap_flush(chunk, page_start, page_end);

    pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
        pcpu_unmap_pages(chunk, pages, populated, rs, re);

    /* no need to flush tlb, vmalloc will handle it lazily */

    pcpu_for_each_pop_region(chunk, rs, re, page_start, page_end)
        pcpu_free_pages(chunk, pages, populated, rs, re);

    /* commit new bitmap */
    bitmap_copy(chunk->populated, populated, pcpu_unit_pages);
}

static struct pcpu_chunk *pcpu_create_chunk(void)
{
    struct pcpu_chunk *chunk;
    struct vm_struct **vms;

    chunk = pcpu_alloc_chunk();
    if (!chunk)
        return NULL;

    vms = pcpu_get_vm_areas(pcpu_group_offsets, pcpu_group_sizes,
                pcpu_nr_groups, pcpu_atom_size);
    if (!vms) {
        pcpu_free_chunk(chunk);
        return NULL;
    }

    chunk->data = vms;
    chunk->base_addr = vms[0]->addr - pcpu_group_offsets[0];
    return chunk;
}

static void pcpu_destroy_chunk(struct pcpu_chunk *chunk)
{
    if (chunk && chunk->data)
        pcpu_free_vm_areas(chunk->data, pcpu_nr_groups);
    pcpu_free_chunk(chunk);
}

static struct page *pcpu_addr_to_page(void *addr)
{
    return vmalloc_to_page(addr);
}

static int __init pcpu_verify_alloc_info(const struct pcpu_alloc_info *ai)
{
    /* no extra restriction */
    return 0;
}