1 /*
2 * linux/mm/page_io.c
3 *
4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 *
6 * Swap reorganised 29.12.95,
7 * Asynchronous swapping added 30.12.95. Stephen Tweedie
8 * Removed race in async swapping. 14.4.1996. Bruno Haible
9 * Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
10 * Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
11 */
12
13 #include <linux/mm.h>
14 #include <linux/kernel_stat.h>
15 #include <linux/pagemap.h>
16 #include <linux/swap.h>
17 #include <linux/bio.h>
18 #include <linux/swapops.h>
19 #include <linux/writeback.h>
20 #include <asm/pgtable.h>
21
22 static struct bio *get_swap_bio(int gfp_flags, pgoff_t index,
23 struct page *page, bio_end_io_t end_io)
24 {
25 struct bio *bio;
26
27 bio = bio_alloc(gfp_flags, 1);
28 if (bio) {
29 struct swap_info_struct *sis;
30 swp_entry_t entry = { .val = index, };
31
32 sis = get_swap_info_struct(swp_type(entry));
33 bio->bi_sector = map_swap_page(sis, swp_offset(entry)) *
34 (PAGE_SIZE >> 9);
35 bio->bi_bdev = sis->bdev;
36 bio->bi_io_vec[0].bv_page = page;
37 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
38 bio->bi_io_vec[0].bv_offset = 0;
39 bio->bi_vcnt = 1;
40 bio->bi_idx = 0;
41 bio->bi_size = PAGE_SIZE;
42 bio->bi_end_io = end_io;
43 }
44 return bio;
45 }
46
47 static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err)
48 {
49 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
50 struct page *page = bio->bi_io_vec[0].bv_page;
51
52 if (bio->bi_size)
53 return 1;
54
55 if (!uptodate)
56 SetPageError(page);
57 end_page_writeback(page);
58 bio_put(bio);
59 return 0;
60 }
61
62 static int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
63 {
64 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
65 struct page *page = bio->bi_io_vec[0].bv_page;
66
67 if (bio->bi_size)
68 return 1;
69
70 if (!uptodate) {
71 SetPageError(page);
72 ClearPageUptodate(page);
73 } else {
74 SetPageUptodate(page);
75 }
76 unlock_page(page);
77 bio_put(bio);
78 return 0;
79 }
80
81 /*
82 * We may have stale swap cache pages in memory: notice
83 * them here and get rid of the unnecessary final write.
84 */
85 int swap_writepage(struct page *page, struct writeback_control *wbc)
86 {
87 struct bio *bio;
88 int ret = 0, rw = WRITE;
89
90 if (remove_exclusive_swap_page(page)) {
91 unlock_page(page);
92 goto out;
93 }
94 bio = get_swap_bio(GFP_NOIO, page->private, page, end_swap_bio_write);
95 if (bio == NULL) {
96 set_page_dirty(page);
97 unlock_page(page);
98 ret = -ENOMEM;
99 goto out;
100 }
101 if (wbc->sync_mode == WB_SYNC_ALL)
102 rw |= (1 << BIO_RW_SYNC);
103 inc_page_state(pswpout);
104 set_page_writeback(page);
105 unlock_page(page);
106 submit_bio(rw, bio);
107 out:
108 return ret;
109 }
110
111 int swap_readpage(struct file *file, struct page *page)
112 {
113 struct bio *bio;
114 int ret = 0;
115
116 BUG_ON(!PageLocked(page));
117 ClearPageUptodate(page);
118 bio = get_swap_bio(GFP_KERNEL, page->private, page, end_swap_bio_read);
119 if (bio == NULL) {
120 unlock_page(page);
121 ret = -ENOMEM;
122 goto out;
123 }
124 inc_page_state(pswpin);
125 submit_bio(READ, bio);
126 out:
127 return ret;
128 }
129
130 #if defined(CONFIG_SOFTWARE_SUSPEND) || defined(CONFIG_PM_DISK)
131 /*
132 * A scruffy utility function to read or write an arbitrary swap page
133 * and wait on the I/O. The caller must have a ref on the page.
134 *
135 * We use end_swap_bio_read() even for writes, because it happens to do what
136 * we want.
137 */
138 int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page)
139 {
140 struct bio *bio;
141 int ret = 0;
142
143 lock_page(page);
144
145 bio = get_swap_bio(GFP_KERNEL, entry.val, page, end_swap_bio_read);
146 if (bio == NULL) {
147 unlock_page(page);
148 ret = -ENOMEM;
149 goto out;
150 }
151
152 submit_bio(rw | (1 << BIO_RW_SYNC), bio);
153 wait_on_page_locked(page);
154
155 if (!PageUptodate(page) || PageError(page))
156 ret = -EIO;
157 out:
158 return ret;
159 }
160 #endif
161
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