LXR linux/net/ceph/pagelist.c

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