pagelist.c revision ae86b9e3846f6fc5509dee721f2bdba1db8ab96a 
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/* Allocate enough pages for a pagelist to append the given amount
76 * of data without without allocating.
77 * Returns: 0 on success, -ENOMEM on error.
78 */
79int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
80{
81	if (space <= pl->room)
82		return 0;
83	space -= pl->room;
84	space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */
85
86	while (space > pl->num_pages_free) {
87		struct page *page = __page_cache_alloc(GFP_NOFS);
88		if (!page)
89			return -ENOMEM;
90		list_add_tail(&page->lru, &pl->free_list);
91		++pl->num_pages_free;
92	}
93	return 0;
94}
95EXPORT_SYMBOL(ceph_pagelist_reserve);
96
97/* Free any pages that have been preallocated. */
98int ceph_pagelist_free_reserve(struct ceph_pagelist *pl)
99{
100	while (!list_empty(&pl->free_list)) {
101		struct page *page = list_first_entry(&pl->free_list,
102						     struct page, lru);
103		list_del(&page->lru);
104		__free_page(page);
105		--pl->num_pages_free;
106	}
107	BUG_ON(pl->num_pages_free);
108	return 0;
109}
110EXPORT_SYMBOL(ceph_pagelist_free_reserve);
111
112/* Create a truncation point. */
113void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,
114			      struct ceph_pagelist_cursor *c)
115{
116	c->pl = pl;
117	c->page_lru = pl->head.prev;
118	c->room = pl->room;
119}
120EXPORT_SYMBOL(ceph_pagelist_set_cursor);
121
122/* Truncate a pagelist to the given point. Move extra pages to reserve.
123 * This won't sleep.
124 * Returns: 0 on success,
125 *          -EINVAL if the pagelist doesn't match the trunc point pagelist
126 */
127int ceph_pagelist_truncate(struct ceph_pagelist *pl,
128			   struct ceph_pagelist_cursor *c)
129{
130	struct page *page;
131
132	if (pl != c->pl)
133		return -EINVAL;
134	ceph_pagelist_unmap_tail(pl);
135	while (pl->head.prev != c->page_lru) {
136		page = list_entry(pl->head.prev, struct page, lru);
137		list_del(&page->lru);                /* remove from pagelist */
138		list_add_tail(&page->lru, &pl->free_list); /* add to reserve */
139		++pl->num_pages_free;
140	}
141	pl->room = c->room;
142	if (!list_empty(&pl->head)) {
143		page = list_entry(pl->head.prev, struct page, lru);
144		pl->mapped_tail = kmap(page);
145	}
146	return 0;
147}
148EXPORT_SYMBOL(ceph_pagelist_truncate);
149