net/ceph/pagelist.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/module.h>
   3 #include <linux/gfp.h>
   4 #include <linux/slab.h>
   5 #include <linux/pagemap.h>
   6 #include <linux/highmem.h>
   7 #include <linux/ceph/pagelist.h>
   8
   9 static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)
  10 {
  11         if (pl->mapped_tail) {
  12                 struct page *page = list_entry(pl->head.prev, struct page, lru);
  13                 kunmap(page);
  14                 pl->mapped_tail = NULL;
  15         }
  16 }
  17
  18 void ceph_pagelist_release(struct ceph_pagelist *pl)
  19 {
  20         if (!refcount_dec_and_test(&pl->refcnt))
  21                 return;
  22         ceph_pagelist_unmap_tail(pl);
  23         while (!list_empty(&pl->head)) {
  24                 struct page *page = list_first_entry(&pl->head, struct page,
  25                                                      lru);
  26                 list_del(&page->lru);
  27                 __free_page(page);
  28         }
  29         ceph_pagelist_free_reserve(pl);
  30         kfree(pl);
  31 }
  32 EXPORT_SYMBOL(ceph_pagelist_release);
  33
  34 static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
  35 {
  36         struct page *page;
  37
  38         if (!pl->num_pages_free) {
  39                 page = __page_cache_alloc(GFP_NOFS);
  40         } else {
  41                 page = list_first_entry(&pl->free_list, struct page, lru);
  42                 list_del(&page->lru);
  43                 --pl->num_pages_free;
  44         }
  45         if (!page)
  46                 return -ENOMEM;
  47         pl->room += PAGE_SIZE;
  48         ceph_pagelist_unmap_tail(pl);
  49         list_add_tail(&page->lru, &pl->head);
  50         pl->mapped_tail = kmap(page);
  51         return 0;
  52 }
  53
  54 int ceph_pagelist_append(struct ceph_pagelist *pl, const void *buf, size_t len)
  55 {
  56         while (pl->room < len) {
  57                 size_t bit = pl->room;
  58                 int ret;
  59
  60                 memcpy(pl->mapped_tail + (pl->length & ~PAGE_MASK),
  61                        buf, bit);
  62                 pl->length += bit;
  63                 pl->room -= bit;
  64                 buf += bit;
  65                 len -= bit;
  66                 ret = ceph_pagelist_addpage(pl);
  67                 if (ret)
  68                         return ret;
  69         }
  70
  71         memcpy(pl->mapped_tail + (pl->length & ~PAGE_MASK), buf, len);
  72         pl->length += len;
  73         pl->room -= len;
  74         return 0;
  75 }
  76 EXPORT_SYMBOL(ceph_pagelist_append);
  77
  78 /* Allocate enough pages for a pagelist to append the given amount
  79  * of data without without allocating.
  80  * Returns: 0 on success, -ENOMEM on error.
  81  */
  82 int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
  83 {
  84         if (space <= pl->room)
  85                 return 0;
  86         space -= pl->room;
  87         space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */
  88
  89         while (space > pl->num_pages_free) {
  90                 struct page *page = __page_cache_alloc(GFP_NOFS);
  91                 if (!page)
  92                         return -ENOMEM;
  93                 list_add_tail(&page->lru, &pl->free_list);
  94                 ++pl->num_pages_free;
  95         }
  96         return 0;
  97 }
  98 EXPORT_SYMBOL(ceph_pagelist_reserve);
  99
 100 /* Free any pages that have been preallocated. */
 101 int 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 }
 113 EXPORT_SYMBOL(ceph_pagelist_free_reserve);
 114
 115 /* Create a truncation point. */
 116 void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,
 117                               struct ceph_pagelist_cursor *c)
 118 {
 119         c->pl = pl;
 120         c->page_lru = pl->head.prev;
 121         c->room = pl->room;
 122 }
 123 EXPORT_SYMBOL(ceph_pagelist_set_cursor);
 124
 125 /* Truncate a pagelist to the given point. Move extra pages to reserve.
 126  * This won't sleep.
 127  * Returns: 0 on success,
 128  *          -EINVAL if the pagelist doesn't match the trunc point pagelist
 129  */
 130 int ceph_pagelist_truncate(struct ceph_pagelist *pl,
 131                            struct ceph_pagelist_cursor *c)
 132 {
 133         struct page *page;
 134
 135         if (pl != c->pl)
 136                 return -EINVAL;
 137         ceph_pagelist_unmap_tail(pl);
 138         while (pl->head.prev != c->page_lru) {
 139                 page = list_entry(pl->head.prev, struct page, lru);
 140                 /* move from pagelist to reserve */
 141                 list_move_tail(&page->lru, &pl->free_list);
 142                 ++pl->num_pages_free;
 143         }
 144         pl->room = c->room;
 145         if (!list_empty(&pl->head)) {
 146                 page = list_entry(pl->head.prev, struct page, lru);
 147                 pl->mapped_tail = kmap(page);
 148         }
 149         return 0;
 150 }
 151 EXPORT_SYMBOL(ceph_pagelist_truncate);