xref: /linux/net/ceph/pagelist.c (revision 9d0ad045533ee37a208991ac5baaf6641e60a9ed)
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 
ceph_pagelist_alloc(gfp_t gfp_flags)9 struct ceph_pagelist *ceph_pagelist_alloc(gfp_t gfp_flags)
10 {
11 	struct ceph_pagelist *pl;
12 
13 	pl = kmalloc(sizeof(*pl), gfp_flags);
14 	if (!pl)
15 		return NULL;
16 
17 	INIT_LIST_HEAD(&pl->head);
18 	pl->mapped_tail = NULL;
19 	pl->length = 0;
20 	pl->room = 0;
21 	INIT_LIST_HEAD(&pl->free_list);
22 	pl->num_pages_free = 0;
23 	refcount_set(&pl->refcnt, 1);
24 
25 	return pl;
26 }
27 EXPORT_SYMBOL(ceph_pagelist_alloc);
28 
ceph_pagelist_unmap_tail(struct ceph_pagelist * pl)29 static void ceph_pagelist_unmap_tail(struct ceph_pagelist *pl)
30 {
31 	if (pl->mapped_tail) {
32 		struct page *page = list_entry(pl->head.prev, struct page, lru);
33 		kunmap(page);
34 		pl->mapped_tail = NULL;
35 	}
36 }
37 
ceph_pagelist_release(struct ceph_pagelist * pl)38 void ceph_pagelist_release(struct ceph_pagelist *pl)
39 {
40 	if (!refcount_dec_and_test(&pl->refcnt))
41 		return;
42 	ceph_pagelist_unmap_tail(pl);
43 	while (!list_empty(&pl->head)) {
44 		struct page *page = list_first_entry(&pl->head, struct page,
45 						     lru);
46 		list_del(&page->lru);
47 		__free_page(page);
48 	}
49 	ceph_pagelist_free_reserve(pl);
50 	kfree(pl);
51 }
52 EXPORT_SYMBOL(ceph_pagelist_release);
53 
ceph_pagelist_addpage(struct ceph_pagelist * pl)54 static int ceph_pagelist_addpage(struct ceph_pagelist *pl)
55 {
56 	struct page *page;
57 
58 	if (!pl->num_pages_free) {
59 		page = __page_cache_alloc(GFP_NOFS);
60 	} else {
61 		page = list_first_entry(&pl->free_list, struct page, lru);
62 		list_del(&page->lru);
63 		--pl->num_pages_free;
64 	}
65 	if (!page)
66 		return -ENOMEM;
67 	pl->room += PAGE_SIZE;
68 	ceph_pagelist_unmap_tail(pl);
69 	list_add_tail(&page->lru, &pl->head);
70 	pl->mapped_tail = kmap(page);
71 	return 0;
72 }
73 
ceph_pagelist_append(struct ceph_pagelist * pl,const void * buf,size_t len)74 int ceph_pagelist_append(struct ceph_pagelist *pl, const void *buf, size_t len)
75 {
76 	while (pl->room < len) {
77 		size_t bit = pl->room;
78 		int ret;
79 
80 		memcpy(pl->mapped_tail + (pl->length & ~PAGE_MASK),
81 		       buf, bit);
82 		pl->length += bit;
83 		pl->room -= bit;
84 		buf += bit;
85 		len -= bit;
86 		ret = ceph_pagelist_addpage(pl);
87 		if (ret)
88 			return ret;
89 	}
90 
91 	memcpy(pl->mapped_tail + (pl->length & ~PAGE_MASK), buf, len);
92 	pl->length += len;
93 	pl->room -= len;
94 	return 0;
95 }
96 EXPORT_SYMBOL(ceph_pagelist_append);
97 
98 /* Allocate enough pages for a pagelist to append the given amount
99  * of data without allocating.
100  * Returns: 0 on success, -ENOMEM on error.
101  */
ceph_pagelist_reserve(struct ceph_pagelist * pl,size_t space)102 int ceph_pagelist_reserve(struct ceph_pagelist *pl, size_t space)
103 {
104 	if (space <= pl->room)
105 		return 0;
106 	space -= pl->room;
107 	space = (space + PAGE_SIZE - 1) >> PAGE_SHIFT;   /* conv to num pages */
108 
109 	while (space > pl->num_pages_free) {
110 		struct page *page = __page_cache_alloc(GFP_NOFS);
111 		if (!page)
112 			return -ENOMEM;
113 		list_add_tail(&page->lru, &pl->free_list);
114 		++pl->num_pages_free;
115 	}
116 	return 0;
117 }
118 EXPORT_SYMBOL(ceph_pagelist_reserve);
119 
120 /* Free any pages that have been preallocated. */
ceph_pagelist_free_reserve(struct ceph_pagelist * pl)121 int ceph_pagelist_free_reserve(struct ceph_pagelist *pl)
122 {
123 	while (!list_empty(&pl->free_list)) {
124 		struct page *page = list_first_entry(&pl->free_list,
125 						     struct page, lru);
126 		list_del(&page->lru);
127 		__free_page(page);
128 		--pl->num_pages_free;
129 	}
130 	BUG_ON(pl->num_pages_free);
131 	return 0;
132 }
133 EXPORT_SYMBOL(ceph_pagelist_free_reserve);
134