page_io.c revision 7b6d91daee5cac6402186ff224c3af39d79f4a0e 
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
23static 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
43static 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
69void 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 */
92int 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);
114out:
115	return ret;
116}
117
118int 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);
133out:
134	return ret;
135}
136