xref: /openbmc/linux/mm/page_io.c (revision 9d56dd3b083a3bec56e9da35ce07baca81030b03)
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(gfp_t gfp_flags,
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 		bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
30 		bio->bi_sector <<= PAGE_SHIFT - 9;
31 		bio->bi_io_vec[0].bv_page = page;
32 		bio->bi_io_vec[0].bv_len = PAGE_SIZE;
33 		bio->bi_io_vec[0].bv_offset = 0;
34 		bio->bi_vcnt = 1;
35 		bio->bi_idx = 0;
36 		bio->bi_size = PAGE_SIZE;
37 		bio->bi_end_io = end_io;
38 	}
39 	return bio;
40 }
41 
42 static void end_swap_bio_write(struct bio *bio, int err)
43 {
44 	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
45 	struct page *page = bio->bi_io_vec[0].bv_page;
46 
47 	if (!uptodate) {
48 		SetPageError(page);
49 		/*
50 		 * We failed to write the page out to swap-space.
51 		 * Re-dirty the page in order to avoid it being reclaimed.
52 		 * Also print a dire warning that things will go BAD (tm)
53 		 * very quickly.
54 		 *
55 		 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
56 		 */
57 		set_page_dirty(page);
58 		printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
59 				imajor(bio->bi_bdev->bd_inode),
60 				iminor(bio->bi_bdev->bd_inode),
61 				(unsigned long long)bio->bi_sector);
62 		ClearPageReclaim(page);
63 	}
64 	end_page_writeback(page);
65 	bio_put(bio);
66 }
67 
68 void end_swap_bio_read(struct bio *bio, int err)
69 {
70 	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
71 	struct page *page = bio->bi_io_vec[0].bv_page;
72 
73 	if (!uptodate) {
74 		SetPageError(page);
75 		ClearPageUptodate(page);
76 		printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
77 				imajor(bio->bi_bdev->bd_inode),
78 				iminor(bio->bi_bdev->bd_inode),
79 				(unsigned long long)bio->bi_sector);
80 	} else {
81 		SetPageUptodate(page);
82 	}
83 	unlock_page(page);
84 	bio_put(bio);
85 }
86 
87 /*
88  * We may have stale swap cache pages in memory: notice
89  * them here and get rid of the unnecessary final write.
90  */
91 int swap_writepage(struct page *page, struct writeback_control *wbc)
92 {
93 	struct bio *bio;
94 	int ret = 0, rw = WRITE;
95 
96 	if (try_to_free_swap(page)) {
97 		unlock_page(page);
98 		goto out;
99 	}
100 	bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
101 	if (bio == NULL) {
102 		set_page_dirty(page);
103 		unlock_page(page);
104 		ret = -ENOMEM;
105 		goto out;
106 	}
107 	if (wbc->sync_mode == WB_SYNC_ALL)
108 		rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
109 	count_vm_event(PSWPOUT);
110 	set_page_writeback(page);
111 	unlock_page(page);
112 	submit_bio(rw, bio);
113 out:
114 	return ret;
115 }
116 
117 int swap_readpage(struct page *page)
118 {
119 	struct bio *bio;
120 	int ret = 0;
121 
122 	VM_BUG_ON(!PageLocked(page));
123 	VM_BUG_ON(PageUptodate(page));
124 	bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
125 	if (bio == NULL) {
126 		unlock_page(page);
127 		ret = -ENOMEM;
128 		goto out;
129 	}
130 	count_vm_event(PSWPIN);
131 	submit_bio(READ, bio);
132 out:
133 	return ret;
134 }
135