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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/gfp.h> | |
16 | #include <linux/pagemap.h> | |
17 | #include <linux/swap.h> | |
18 | #include <linux/bio.h> | |
19 | #include <linux/swapops.h> | |
20 | #include <linux/writeback.h> | |
21 | #include <asm/pgtable.h> | |
22 | ||
23 | static struct bio *get_swap_bio(gfp_t gfp_flags, | |
24 | struct page *page, bio_end_io_t end_io) | |
25 | { | |
26 | struct bio *bio; | |
27 | ||
28 | bio = bio_alloc(gfp_flags, 1); | |
29 | if (bio) { | |
30 | bio->bi_sector = map_swap_page(page, &bio->bi_bdev); | |
31 | bio->bi_sector <<= PAGE_SHIFT - 9; | |
32 | bio->bi_io_vec[0].bv_page = page; | |
33 | bio->bi_io_vec[0].bv_len = PAGE_SIZE; | |
34 | bio->bi_io_vec[0].bv_offset = 0; | |
35 | bio->bi_vcnt = 1; | |
36 | bio->bi_idx = 0; | |
37 | bio->bi_size = PAGE_SIZE; | |
38 | bio->bi_end_io = end_io; | |
39 | } | |
40 | return bio; | |
41 | } | |
42 | ||
43 | static void end_swap_bio_write(struct bio *bio, int err) | |
44 | { | |
45 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); | |
46 | struct page *page = bio->bi_io_vec[0].bv_page; | |
47 | ||
48 | if (!uptodate) { | |
49 | SetPageError(page); | |
50 | /* | |
51 | * We failed to write the page out to swap-space. | |
52 | * Re-dirty the page in order to avoid it being reclaimed. | |
53 | * Also print a dire warning that things will go BAD (tm) | |
54 | * very quickly. | |
55 | * | |
56 | * Also clear PG_reclaim to avoid rotate_reclaimable_page() | |
57 | */ | |
58 | set_page_dirty(page); | |
59 | printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n", | |
60 | imajor(bio->bi_bdev->bd_inode), | |
61 | iminor(bio->bi_bdev->bd_inode), | |
62 | (unsigned long long)bio->bi_sector); | |
63 | ClearPageReclaim(page); | |
64 | } | |
65 | end_page_writeback(page); | |
66 | bio_put(bio); | |
67 | } | |
68 | ||
69 | void end_swap_bio_read(struct bio *bio, int err) | |
70 | { | |
71 | const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); | |
72 | struct page *page = bio->bi_io_vec[0].bv_page; | |
73 | ||
74 | if (!uptodate) { | |
75 | SetPageError(page); | |
76 | ClearPageUptodate(page); | |
77 | printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n", | |
78 | imajor(bio->bi_bdev->bd_inode), | |
79 | iminor(bio->bi_bdev->bd_inode), | |
80 | (unsigned long long)bio->bi_sector); | |
81 | } else { | |
82 | SetPageUptodate(page); | |
83 | } | |
84 | unlock_page(page); | |
85 | bio_put(bio); | |
86 | } | |
87 | ||
88 | /* | |
89 | * We may have stale swap cache pages in memory: notice | |
90 | * them here and get rid of the unnecessary final write. | |
91 | */ | |
92 | int swap_writepage(struct page *page, struct writeback_control *wbc) | |
93 | { | |
94 | struct bio *bio; | |
95 | int ret = 0, rw = WRITE; | |
96 | ||
97 | if (try_to_free_swap(page)) { | |
98 | unlock_page(page); | |
99 | goto out; | |
100 | } | |
101 | bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write); | |
102 | if (bio == NULL) { | |
103 | set_page_dirty(page); | |
104 | unlock_page(page); | |
105 | ret = -ENOMEM; | |
106 | goto out; | |
107 | } | |
108 | if (wbc->sync_mode == WB_SYNC_ALL) | |
109 | rw |= REQ_SYNC | REQ_UNPLUG; | |
110 | count_vm_event(PSWPOUT); | |
111 | set_page_writeback(page); | |
112 | unlock_page(page); | |
113 | submit_bio(rw, bio); | |
114 | out: | |
115 | return ret; | |
116 | } | |
117 | ||
118 | int swap_readpage(struct page *page) | |
119 | { | |
120 | struct bio *bio; | |
121 | int ret = 0; | |
122 | ||
123 | VM_BUG_ON(!PageLocked(page)); | |
124 | VM_BUG_ON(PageUptodate(page)); | |
125 | bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read); | |
126 | if (bio == NULL) { | |
127 | unlock_page(page); | |
128 | ret = -ENOMEM; | |
129 | goto out; | |
130 | } | |
131 | count_vm_event(PSWPIN); | |
132 | submit_bio(READ, bio); | |
133 | out: | |
134 | return ret; | |
135 | } |