pagelist.c revision 240634e9b3a8ae2a9e2b7effeea3b9a5b30d68fb 
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/**
76 * Allocate enough pages for a pagelist to append the given amount
77 * of data without without allocating.
78 * Returns: 0 on success, -ENOMEM on error.
79 */
80int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
81{
82	if (space <= pl->room)
83		return 0;
84	space -= pl->room;
85	space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */
86
87	while (space > pl->num_pages_free) {
88		struct page *page = __page_cache_alloc(GFP_NOFS);
89		if (!page)
90			return -ENOMEM;
91		list_add_tail(&page->lru, &pl->free_list);
92		++pl->num_pages_free;
93	}
94	return 0;
95}
96EXPORT_SYMBOL(ceph_pagelist_reserve);
97
98/**
99 * Free any pages that have been preallocated.
100 */
101int 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}
113EXPORT_SYMBOL(ceph_pagelist_free_reserve);
114
115/**
116 * Create a truncation point.
117 */
118void ceph_pagelist_set_cursor(struct ceph_pagelist *pl,
119			      struct ceph_pagelist_cursor *c)
120{
121	c->pl = pl;
122	c->page_lru = pl->head.prev;
123	c->room = pl->room;
124}
125EXPORT_SYMBOL(ceph_pagelist_set_cursor);
126
127/**
128 * Truncate a pagelist to the given point. Move extra pages to reserve.
129 * This won't sleep.
130 * Returns: 0 on success,
131 *          -EINVAL if the pagelist doesn't match the trunc point pagelist
132 */
133int ceph_pagelist_truncate(struct ceph_pagelist *pl,
134			   struct ceph_pagelist_cursor *c)
135{
136	struct page *page;
137
138	if (pl != c->pl)
139		return -EINVAL;
140	ceph_pagelist_unmap_tail(pl);
141	while (pl->head.prev != c->page_lru) {
142		page = list_entry(pl->head.prev, struct page, lru);
143		list_del(&page->lru);                /* remove from pagelist */
144		list_add_tail(&page->lru, &pl->free_list); /* add to reserve */
145		++pl->num_pages_free;
146	}
147	pl->room = c->room;
148	if (!list_empty(&pl->head)) {
149		page = list_entry(pl->head.prev, struct page, lru);
150		pl->mapped_tail = kmap(page);
151	}
152	return 0;
153}
154EXPORT_SYMBOL(ceph_pagelist_truncate);
155