xref: /linux/mm/page_io.c (revision 26b0d14106954ae46d2f4f7eec3481828a210f7d)
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 <linux/frontswap.h>
22 #include <asm/pgtable.h>
23 
24 static struct bio *get_swap_bio(gfp_t gfp_flags,
25 				struct page *page, bio_end_io_t end_io)
26 {
27 	struct bio *bio;
28 
29 	bio = bio_alloc(gfp_flags, 1);
30 	if (bio) {
31 		bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
32 		bio->bi_sector <<= PAGE_SHIFT - 9;
33 		bio->bi_io_vec[0].bv_page = page;
34 		bio->bi_io_vec[0].bv_len = PAGE_SIZE;
35 		bio->bi_io_vec[0].bv_offset = 0;
36 		bio->bi_vcnt = 1;
37 		bio->bi_idx = 0;
38 		bio->bi_size = PAGE_SIZE;
39 		bio->bi_end_io = end_io;
40 	}
41 	return bio;
42 }
43 
44 static void end_swap_bio_write(struct bio *bio, int err)
45 {
46 	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
47 	struct page *page = bio->bi_io_vec[0].bv_page;
48 
49 	if (!uptodate) {
50 		SetPageError(page);
51 		/*
52 		 * We failed to write the page out to swap-space.
53 		 * Re-dirty the page in order to avoid it being reclaimed.
54 		 * Also print a dire warning that things will go BAD (tm)
55 		 * very quickly.
56 		 *
57 		 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
58 		 */
59 		set_page_dirty(page);
60 		printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
61 				imajor(bio->bi_bdev->bd_inode),
62 				iminor(bio->bi_bdev->bd_inode),
63 				(unsigned long long)bio->bi_sector);
64 		ClearPageReclaim(page);
65 	}
66 	end_page_writeback(page);
67 	bio_put(bio);
68 }
69 
70 void end_swap_bio_read(struct bio *bio, int err)
71 {
72 	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
73 	struct page *page = bio->bi_io_vec[0].bv_page;
74 
75 	if (!uptodate) {
76 		SetPageError(page);
77 		ClearPageUptodate(page);
78 		printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
79 				imajor(bio->bi_bdev->bd_inode),
80 				iminor(bio->bi_bdev->bd_inode),
81 				(unsigned long long)bio->bi_sector);
82 	} else {
83 		SetPageUptodate(page);
84 	}
85 	unlock_page(page);
86 	bio_put(bio);
87 }
88 
89 /*
90  * We may have stale swap cache pages in memory: notice
91  * them here and get rid of the unnecessary final write.
92  */
93 int swap_writepage(struct page *page, struct writeback_control *wbc)
94 {
95 	struct bio *bio;
96 	int ret = 0, rw = WRITE;
97 
98 	if (try_to_free_swap(page)) {
99 		unlock_page(page);
100 		goto out;
101 	}
102 	if (frontswap_store(page) == 0) {
103 		set_page_writeback(page);
104 		unlock_page(page);
105 		end_page_writeback(page);
106 		goto out;
107 	}
108 	bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
109 	if (bio == NULL) {
110 		set_page_dirty(page);
111 		unlock_page(page);
112 		ret = -ENOMEM;
113 		goto out;
114 	}
115 	if (wbc->sync_mode == WB_SYNC_ALL)
116 		rw |= REQ_SYNC;
117 	count_vm_event(PSWPOUT);
118 	set_page_writeback(page);
119 	unlock_page(page);
120 	submit_bio(rw, bio);
121 out:
122 	return ret;
123 }
124 
125 int swap_readpage(struct page *page)
126 {
127 	struct bio *bio;
128 	int ret = 0;
129 
130 	VM_BUG_ON(!PageLocked(page));
131 	VM_BUG_ON(PageUptodate(page));
132 	if (frontswap_load(page) == 0) {
133 		SetPageUptodate(page);
134 		unlock_page(page);
135 		goto out;
136 	}
137 	bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
138 	if (bio == NULL) {
139 		unlock_page(page);
140 		ret = -ENOMEM;
141 		goto out;
142 	}
143 	count_vm_event(PSWPIN);
144 	submit_bio(READ, bio);
145 out:
146 	return ret;
147 }
148