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/buffer_head.h>
21#include <linux/writeback.h>
22#include <linux/frontswap.h>
23#include <asm/pgtable.h>
24
25static struct bio *get_swap_bio(gfp_t gfp_flags,
26                struct page *page, bio_end_io_t end_io)
27{
28    struct bio *bio;
29
30    bio = bio_alloc(gfp_flags, 1);
31    if (bio) {
32        bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
33        bio->bi_sector <<= PAGE_SHIFT - 9;
34        bio->bi_io_vec[0].bv_page = page;
35        bio->bi_io_vec[0].bv_len = PAGE_SIZE;
36        bio->bi_io_vec[0].bv_offset = 0;
37        bio->bi_vcnt = 1;
38        bio->bi_idx = 0;
39        bio->bi_size = PAGE_SIZE;
40        bio->bi_end_io = end_io;
41    }
42    return bio;
43}
44
45static void end_swap_bio_write(struct bio *bio, int err)
46{
47    const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
48    struct page *page = bio->bi_io_vec[0].bv_page;
49
50    if (!uptodate) {
51        SetPageError(page);
52        /*
53         * We failed to write the page out to swap-space.
54         * Re-dirty the page in order to avoid it being reclaimed.
55         * Also print a dire warning that things will go BAD (tm)
56         * very quickly.
57         *
58         * Also clear PG_reclaim to avoid rotate_reclaimable_page()
59         */
60        set_page_dirty(page);
61        printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
62                imajor(bio->bi_bdev->bd_inode),
63                iminor(bio->bi_bdev->bd_inode),
64                (unsigned long long)bio->bi_sector);
65        ClearPageReclaim(page);
66    }
67    end_page_writeback(page);
68    bio_put(bio);
69}
70
71void end_swap_bio_read(struct bio *bio, int err)
72{
73    const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
74    struct page *page = bio->bi_io_vec[0].bv_page;
75
76    if (!uptodate) {
77        SetPageError(page);
78        ClearPageUptodate(page);
79        printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
80                imajor(bio->bi_bdev->bd_inode),
81                iminor(bio->bi_bdev->bd_inode),
82                (unsigned long long)bio->bi_sector);
83    } else {
84        SetPageUptodate(page);
85    }
86    unlock_page(page);
87    bio_put(bio);
88}
89
90int generic_swapfile_activate(struct swap_info_struct *sis,
91                struct file *swap_file,
92                sector_t *span)
93{
94    struct address_space *mapping = swap_file->f_mapping;
95    struct inode *inode = mapping->host;
96    unsigned blocks_per_page;
97    unsigned long page_no;
98    unsigned blkbits;
99    sector_t probe_block;
100    sector_t last_block;
101    sector_t lowest_block = -1;
102    sector_t highest_block = 0;
103    int nr_extents = 0;
104    int ret;
105
106    blkbits = inode->i_blkbits;
107    blocks_per_page = PAGE_SIZE >> blkbits;
108
109    /*
110     * Map all the blocks into the extent list. This code doesn't try
111     * to be very smart.
112     */
113    probe_block = 0;
114    page_no = 0;
115    last_block = i_size_read(inode) >> blkbits;
116    while ((probe_block + blocks_per_page) <= last_block &&
117            page_no < sis->max) {
118        unsigned block_in_page;
119        sector_t first_block;
120
121        first_block = bmap(inode, probe_block);
122        if (first_block == 0)
123            goto bad_bmap;
124
125        /*
126         * It must be PAGE_SIZE aligned on-disk
127         */
128        if (first_block & (blocks_per_page - 1)) {
129            probe_block++;
130            goto reprobe;
131        }
132
133        for (block_in_page = 1; block_in_page < blocks_per_page;
134                    block_in_page++) {
135            sector_t block;
136
137            block = bmap(inode, probe_block + block_in_page);
138            if (block == 0)
139                goto bad_bmap;
140            if (block != first_block + block_in_page) {
141                /* Discontiguity */
142                probe_block++;
143                goto reprobe;
144            }
145        }
146
147        first_block >>= (PAGE_SHIFT - blkbits);
148        if (page_no) { /* exclude the header page */
149            if (first_block < lowest_block)
150                lowest_block = first_block;
151            if (first_block > highest_block)
152                highest_block = first_block;
153        }
154
155        /*
156         * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
157         */
158        ret = add_swap_extent(sis, page_no, 1, first_block);
159        if (ret < 0)
160            goto out;
161        nr_extents += ret;
162        page_no++;
163        probe_block += blocks_per_page;
164reprobe:
165        continue;
166    }
167    ret = nr_extents;
168    *span = 1 + highest_block - lowest_block;
169    if (page_no == 0)
170        page_no = 1; /* force Empty message */
171    sis->max = page_no;
172    sis->pages = page_no - 1;
173    sis->highest_bit = page_no - 1;
174out:
175    return ret;
176bad_bmap:
177    printk(KERN_ERR "swapon: swapfile has holes\n");
178    ret = -EINVAL;
179    goto out;
180}
181
182/*
183 * We may have stale swap cache pages in memory: notice
184 * them here and get rid of the unnecessary final write.
185 */
186int swap_writepage(struct page *page, struct writeback_control *wbc)
187{
188    struct bio *bio;
189    int ret = 0, rw = WRITE;
190    struct swap_info_struct *sis = page_swap_info(page);
191
192    if (try_to_free_swap(page)) {
193        unlock_page(page);
194        goto out;
195    }
196    if (frontswap_store(page) == 0) {
197        set_page_writeback(page);
198        unlock_page(page);
199        end_page_writeback(page);
200        goto out;
201    }
202
203    if (sis->flags & SWP_FILE) {
204        struct kiocb kiocb;
205        struct file *swap_file = sis->swap_file;
206        struct address_space *mapping = swap_file->f_mapping;
207        struct iovec iov = {
208            .iov_base = kmap(page),
209            .iov_len = PAGE_SIZE,
210        };
211
212        init_sync_kiocb(&kiocb, swap_file);
213        kiocb.ki_pos = page_file_offset(page);
214        kiocb.ki_left = PAGE_SIZE;
215        kiocb.ki_nbytes = PAGE_SIZE;
216
217        unlock_page(page);
218        ret = mapping->a_ops->direct_IO(KERNEL_WRITE,
219                        &kiocb, &iov,
220                        kiocb.ki_pos, 1);
221        kunmap(page);
222        if (ret == PAGE_SIZE) {
223            count_vm_event(PSWPOUT);
224            ret = 0;
225        }
226        return ret;
227    }
228
229    bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
230    if (bio == NULL) {
231        set_page_dirty(page);
232        unlock_page(page);
233        ret = -ENOMEM;
234        goto out;
235    }
236    if (wbc->sync_mode == WB_SYNC_ALL)
237        rw |= REQ_SYNC;
238    count_vm_event(PSWPOUT);
239    set_page_writeback(page);
240    unlock_page(page);
241    submit_bio(rw, bio);
242out:
243    return ret;
244}
245
246int swap_readpage(struct page *page)
247{
248    struct bio *bio;
249    int ret = 0;
250    struct swap_info_struct *sis = page_swap_info(page);
251
252    VM_BUG_ON(!PageLocked(page));
253    VM_BUG_ON(PageUptodate(page));
254    if (frontswap_load(page) == 0) {
255        SetPageUptodate(page);
256        unlock_page(page);
257        goto out;
258    }
259
260    if (sis->flags & SWP_FILE) {
261        struct file *swap_file = sis->swap_file;
262        struct address_space *mapping = swap_file->f_mapping;
263
264        ret = mapping->a_ops->readpage(swap_file, page);
265        if (!ret)
266            count_vm_event(PSWPIN);
267        return ret;
268    }
269
270    bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
271    if (bio == NULL) {
272        unlock_page(page);
273        ret = -ENOMEM;
274        goto out;
275    }
276    count_vm_event(PSWPIN);
277    submit_bio(READ, bio);
278out:
279    return ret;
280}
281
282int swap_set_page_dirty(struct page *page)
283{
284    struct swap_info_struct *sis = page_swap_info(page);
285
286    if (sis->flags & SWP_FILE) {
287        struct address_space *mapping = sis->swap_file->f_mapping;
288        return mapping->a_ops->set_page_dirty(page);
289    } else {
290        return __set_page_dirty_no_writeback(page);
291    }
292}
293

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