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
   8 static 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
  17 void 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 }
  31 EXPORT_SYMBOL(ceph_pagelist_release);
  32
  33 static 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
  53 int 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 }
  75 EXPORT_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  */
  81 int 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 }
  97 EXPORT_SYMBOL(ceph_pagelist_reserve);
  98
  99 /* Free any pages that have been preallocated. */
 100 int 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 }
 112 EXPORT_SYMBOL(ceph_pagelist_free_reserve);
 113
 114 /* Create a truncation point. */
 115 void 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 }
 122 EXPORT_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  */
 129 int 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 }
 150 EXPORT_SYMBOL(ceph_pagelist_truncate);