page_io.c revision 93dbb393503d53cd226e5e1f0088fe8f4dbaa2b8 
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 void end_swap_bio_write(struct bio *bio, 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 (!uptodate) {
53		SetPageError(page);
54		/*
55		 * We failed to write the page out to swap-space.
56		 * Re-dirty the page in order to avoid it being reclaimed.
57		 * Also print a dire warning that things will go BAD (tm)
58		 * very quickly.
59		 *
60		 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
61		 */
62		set_page_dirty(page);
63		printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
64				imajor(bio->bi_bdev->bd_inode),
65				iminor(bio->bi_bdev->bd_inode),
66				(unsigned long long)bio->bi_sector);
67		ClearPageReclaim(page);
68	}
69	end_page_writeback(page);
70	bio_put(bio);
71}
72
73void end_swap_bio_read(struct bio *bio, int err)
74{
75	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
76	struct page *page = bio->bi_io_vec[0].bv_page;
77
78	if (!uptodate) {
79		SetPageError(page);
80		ClearPageUptodate(page);
81		printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
82				imajor(bio->bi_bdev->bd_inode),
83				iminor(bio->bi_bdev->bd_inode),
84				(unsigned long long)bio->bi_sector);
85	} else {
86		SetPageUptodate(page);
87	}
88	unlock_page(page);
89	bio_put(bio);
90}
91
92/*
93 * We may have stale swap cache pages in memory: notice
94 * them here and get rid of the unnecessary final write.
95 */
96int swap_writepage(struct page *page, struct writeback_control *wbc)
97{
98	struct bio *bio;
99	int ret = 0, rw = WRITE;
100
101	if (try_to_free_swap(page)) {
102		unlock_page(page);
103		goto out;
104	}
105	bio = get_swap_bio(GFP_NOIO, page_private(page), page,
106				end_swap_bio_write);
107	if (bio == NULL) {
108		set_page_dirty(page);
109		unlock_page(page);
110		ret = -ENOMEM;
111		goto out;
112	}
113	if (wbc->sync_mode == WB_SYNC_ALL)
114		rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
115	count_vm_event(PSWPOUT);
116	set_page_writeback(page);
117	unlock_page(page);
118	submit_bio(rw, bio);
119out:
120	return ret;
121}
122
123int swap_readpage(struct file *file, struct page *page)
124{
125	struct bio *bio;
126	int ret = 0;
127
128	VM_BUG_ON(!PageLocked(page));
129	VM_BUG_ON(PageUptodate(page));
130	bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
131				end_swap_bio_read);
132	if (bio == NULL) {
133		unlock_page(page);
134		ret = -ENOMEM;
135		goto out;
136	}
137	count_vm_event(PSWPIN);
138	submit_bio(READ, bio);
139out:
140	return ret;
141}
142