LXR linux/net/ceph/pagelist.c

   1
   2#include <linux/module.h>
   3#include <linux/gfp.h>
   4#include <linux/pagemap.h>
   5#include <linux/highmem.h>
   6#include <linux/ceph/pagelist.h>
   7
   8static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)
   9{
  10        if (pl->mapped_tail) {
  11                struct page *page = list_entry(pl->head.prev, struct page, lru);
  12                kunmap(page);
  13                pl->mapped_tail = NULL;
  14        }
  15}
  16
  17int ceph_pagelist_release(struct ceph_pagelist *pl)
  18{
  19        ceph_pagelist_unmap_tail(pl);
  20        while (!list_empty(&pl->head)) {
  21                struct page *page = list_first_entry(&pl->head, struct page,
  22                                                     lru);
  23                list_del(&page->lru);
  24                __free_page(page);
  25        }
  26        ceph_pagelist_free_reserve(pl);
  27        return 0;
  28}
  29EXPORT_SYMBOL(ceph_pagelist_release);
  30
  31static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
  32{
  33        struct page *page;
  34
  35        if (!pl->num_pages_free) {
  36                page = __page_cache_alloc(GFP_NOFS);
  37        } else {
  38                page = list_first_entry(&pl->free_list, struct page, lru);
  39                list_del(&page->lru);
  40                --pl->num_pages_free;
  41        }
  42        if (!page)
  43                return -ENOMEM;
  44        pl->room += PAGE_SIZE;
  45        ceph_pagelist_unmap_tail(pl);
  46        list_add_tail(&page->lru, &pl->head);
  47        pl->mapped_tail = kmap(page);
  48        return 0;
  49}
  50
  51int ceph_pagelist_append(struct ceph_pagelist *pl, const void *buf, size_t len)
  52{
  53        while (pl->room < len) {
  54                size_t bit = pl->room;
  55                int ret;
  56
  57                memcpy(pl->mapped_tail + (pl->length & ~PAGE_CACHE_MASK),
  58                       buf, bit);
  59                pl->length += bit;
  60                pl->room -= bit;
  61                buf += bit;
  62                len -= bit;
  63                ret = ceph_pagelist_addpage(pl);
  64                if (ret)
  65                        return ret;
  66        }
  67
  68        memcpy(pl->mapped_tail + (pl->length & ~PAGE_CACHE_MASK), buf, len);
  69        pl->length += len;
  70        pl->room -= len;
  71        return 0;
  72}
  73EXPORT_SYMBOL(ceph_pagelist_append);
  74
  75/**
  76 * Allocate enough pages for a pagelist to append the given amount
  77 * of data without without allocating.
  78 * Returns: 0 on success, -ENOMEM on error.
  79 */
  80int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
  81{
  82        if (space <= pl->room)
  83                return 0;
  84        space -= pl->room;
  85        space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */
  86
  87        while (space > pl->num_pages_free) {
  88                struct page *page = __page_cache_alloc(GFP_NOFS);
  89                if (!page)
  90                        return -ENOMEM;
  91                list_add_tail(&page->lru, &pl->free_list);
  92                ++pl->num_pages_free;
  93        }
  94        return 0;
  95}
  96EXPORT_SYMBOL(ceph_pagelist_reserve);
  97
  98/**
  99 * Free any pages that have been preallocated.
 100 */
 101int ceph_pagelist_free_reserve(struct ceph_pagelist *pl)
 102{
 103        while (!list_empty(&pl->free_list)) {
 104                struct page *page = list_first_entry(&pl->free_list,
 105                                                     struct page, lru);
 106                list_del(&page->lru);
 107                __free_page(page);
 108                --pl->num_pages_free;
 109        }
 110        BUG_ON(pl->num_pages_free);
 111        return 0;
 112}
 113EXPORT_SYMBOL(ceph_pagelist_free_reserve);
 114
 115/**
 116 * Create a truncation point.
 117 */
 118void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,
 119                              struct ceph_pagelist_cursor *c)
 120{
 121        c->pl = pl;
 122        c->page_lru = pl->head.prev;
 123        c->room = pl->room;
 124}
 125EXPORT_SYMBOL(ceph_pagelist_set_cursor);
 126
 127/**
 128 * Truncate a pagelist to the given point. Move extra pages to reserve.
 129 * This won't sleep.
 130 * Returns: 0 on success,
 131 *          -EINVAL if the pagelist doesn't match the trunc point pagelist
 132 */
 133int ceph_pagelist_truncate(struct ceph_pagelist *pl,
 134                           struct ceph_pagelist_cursor *c)
 135{
 136        struct page *page;
 137
 138        if (pl != c->pl)
 139                return -EINVAL;
 140        ceph_pagelist_unmap_tail(pl);
 141        while (pl->head.prev != c->page_lru) {
 142                page = list_entry(pl->head.prev, struct page, lru);
 143                list_del(&page->lru);                /* remove from pagelist */
 144                list_add_tail(&page->lru, &pl->free_list); /* add to reserve */
 145                ++pl->num_pages_free;
 146        }
 147        pl->room = c->room;
 148        if (!list_empty(&pl->head)) {
 149                page = list_entry(pl->head.prev, struct page, lru);
 150                pl->mapped_tail = kmap(page);
 151        }
 152        return 0;
 153}
 154EXPORT_SYMBOL(ceph_pagelist_truncate);
 155