pagelist.c

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#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/ceph/pagelist.h>

static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)
{
    if (pl->mapped_tail) {
        struct page *page = list_entry(pl->head.prev, struct page, lru);
        kunmap(page);
        pl->mapped_tail = NULL;
    }
}

int ceph_pagelist_release(struct ceph_pagelist *pl)
{
    ceph_pagelist_unmap_tail(pl);
    while (!list_empty(&pl->head)) {
        struct page *page = list_first_entry(&pl->head, struct page,
                             lru);
        list_del(&page->lru);
        __free_page(page);
    }
    ceph_pagelist_free_reserve(pl);
    return 0;
}
EXPORT_SYMBOL(ceph_pagelist_release);

static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
{
    struct page *page;

    if (!pl->num_pages_free) {
        page = __page_cache_alloc(GFP_NOFS);
    } else {
        page = list_first_entry(&pl->free_list, struct page, lru);
        list_del(&page->lru);
        --pl->num_pages_free;
    }
    if (!page)
        return -ENOMEM;
    pl->room += PAGE_SIZE;
    ceph_pagelist_unmap_tail(pl);
    list_add_tail(&page->lru, &pl->head);
    pl->mapped_tail = kmap(page);
    return 0;
}

int ceph_pagelist_append(struct ceph_pagelist *pl, const void *buf, size_t len)
{
    while (pl->room < len) {
        size_t bit = pl->room;
        int ret;

        memcpy(pl->mapped_tail + (pl->length & ~PAGE_CACHE_MASK),
               buf, bit);
        pl->length += bit;
        pl->room -= bit;
        buf += bit;
        len -= bit;
        ret = ceph_pagelist_addpage(pl);
        if (ret)
            return ret;
    }

    memcpy(pl->mapped_tail + (pl->length & ~PAGE_CACHE_MASK), buf, len);
    pl->length += len;
    pl->room -= len;
    return 0;
}
EXPORT_SYMBOL(ceph_pagelist_append);

/* Allocate enough pages for a pagelist to append the given amount
 * of data without without allocating.
 * Returns: 0 on success, -ENOMEM on error.
 */
int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
{
    if (space <= pl->room)
        return 0;
    space -= pl->room;
    space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */

    while (space > pl->num_pages_free) {
        struct page *page = __page_cache_alloc(GFP_NOFS);
        if (!page)
            return -ENOMEM;
        list_add_tail(&page->lru, &pl->free_list);
        ++pl->num_pages_free;
    }
    return 0;
}
EXPORT_SYMBOL(ceph_pagelist_reserve);

/* Free any pages that have been preallocated. */
int ceph_pagelist_free_reserve(struct ceph_pagelist *pl)
{
    while (!list_empty(&pl->free_list)) {
        struct page *page = list_first_entry(&pl->free_list,
                             struct page, lru);
        list_del(&page->lru);
        __free_page(page);
        --pl->num_pages_free;
    }
    BUG_ON(pl->num_pages_free);
    return 0;
}
EXPORT_SYMBOL(ceph_pagelist_free_reserve);

/* Create a truncation point. */
void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,
                  struct ceph_pagelist_cursor *c)
{
    c->pl = pl;
    c->page_lru = pl->head.prev;
    c->room = pl->room;
}
EXPORT_SYMBOL(ceph_pagelist_set_cursor);

/* Truncate a pagelist to the given point. Move extra pages to reserve.
 * This won't sleep.
 * Returns: 0 on success,
 *          -EINVAL if the pagelist doesn't match the trunc point pagelist
 */
int ceph_pagelist_truncate(struct ceph_pagelist *pl,
               struct ceph_pagelist_cursor *c)
{
    struct page *page;

    if (pl != c->pl)
        return -EINVAL;
    ceph_pagelist_unmap_tail(pl);
    while (pl->head.prev != c->page_lru) {
        page = list_entry(pl->head.prev, struct page, lru);
        /* move from pagelist to reserve */
        list_move_tail(&page->lru, &pl->free_list);
        ++pl->num_pages_free;
    }
    pl->room = c->room;
    if (!list_empty(&pl->head)) {
        page = list_entry(pl->head.prev, struct page, lru);
        pl->mapped_tail = kmap(page);
    }
    return 0;
}
EXPORT_SYMBOL(ceph_pagelist_truncate);