LXR linux/net/ceph/pagelist.c

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