page_io.c revision f8891e5e1f93a128c3900f82035e8541357896a7 
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
22static struct bio *get_swap_bio(gfp_t 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
47static 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
62static 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 */
85int 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), page,
95				end_swap_bio_write);
96	if (bio == NULL) {
97		set_page_dirty(page);
98		unlock_page(page);
99		ret = -ENOMEM;
100		goto out;
101	}
102	if (wbc->sync_mode == WB_SYNC_ALL)
103		rw |= (1 << BIO_RW_SYNC);
104	count_vm_event(PSWPOUT);
105	set_page_writeback(page);
106	unlock_page(page);
107	submit_bio(rw, bio);
108out:
109	return ret;
110}
111
112int swap_readpage(struct file *file, struct page *page)
113{
114	struct bio *bio;
115	int ret = 0;
116
117	BUG_ON(!PageLocked(page));
118	ClearPageUptodate(page);
119	bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
120				end_swap_bio_read);
121	if (bio == NULL) {
122		unlock_page(page);
123		ret = -ENOMEM;
124		goto out;
125	}
126	count_vm_event(PSWPIN);
127	submit_bio(READ, bio);
128out:
129	return ret;
130}
131
132#ifdef CONFIG_SOFTWARE_SUSPEND
133/*
134 * A scruffy utility function to read or write an arbitrary swap page
135 * and wait on the I/O.  The caller must have a ref on the page.
136 *
137 * We use end_swap_bio_read() even for writes, because it happens to do what
138 * we want.
139 */
140int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page)
141{
142	struct bio *bio;
143	int ret = 0;
144
145	lock_page(page);
146
147	bio = get_swap_bio(GFP_KERNEL, entry.val, page, end_swap_bio_read);
148	if (bio == NULL) {
149		unlock_page(page);
150		ret = -ENOMEM;
151		goto out;
152	}
153
154	submit_bio(rw | (1 << BIO_RW_SYNC), bio);
155	wait_on_page_locked(page);
156
157	if (!PageUptodate(page) || PageError(page))
158		ret = -EIO;
159out:
160	return ret;
161}
162#endif
163