Root/mm/page_io.c

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;
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

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