a8a3ef45fed753b68ac1cc4a94c9260979a37879
[linux-3.10.git] / 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 <linux/aio.h>
24 #include <asm/pgtable.h>
25
26 static struct bio *get_swap_bio(gfp_t gfp_flags,
27                                 struct page *page, bio_end_io_t end_io)
28 {
29         struct bio *bio;
30
31         bio = bio_alloc(gfp_flags, 1);
32         if (bio) {
33                 bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
34                 bio->bi_sector <<= PAGE_SHIFT - 9;
35                 bio->bi_io_vec[0].bv_page = page;
36                 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
37                 bio->bi_io_vec[0].bv_offset = 0;
38                 bio->bi_vcnt = 1;
39                 bio->bi_size = PAGE_SIZE;
40                 bio->bi_end_io = end_io;
41         }
42         return bio;
43 }
44
45 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
71 void 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
90 int 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;
164 reprobe:
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;
174 out:
175         return ret;
176 bad_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  */
186 int swap_writepage(struct page *page, struct writeback_control *wbc)
187 {
188         int ret = 0;
189
190         if (try_to_free_swap(page)) {
191                 unlock_page(page);
192                 goto out;
193         }
194         if (frontswap_store(page) == 0) {
195                 set_page_writeback(page);
196                 unlock_page(page);
197                 end_page_writeback(page);
198                 goto out;
199         }
200         ret = __swap_writepage(page, wbc, end_swap_bio_write);
201 out:
202         return ret;
203 }
204
205 int __swap_writepage(struct page *page, struct writeback_control *wbc,
206         void (*end_write_func)(struct bio *, int))
207 {
208         struct bio *bio;
209         int ret = 0, rw = WRITE;
210         struct swap_info_struct *sis = page_swap_info(page);
211
212         if (sis->flags & SWP_FILE) {
213                 struct kiocb kiocb;
214                 struct file *swap_file = sis->swap_file;
215                 struct address_space *mapping = swap_file->f_mapping;
216                 struct iovec iov = {
217                         .iov_base = kmap(page),
218                         .iov_len  = PAGE_SIZE,
219                 };
220
221                 init_sync_kiocb(&kiocb, swap_file);
222                 kiocb.ki_pos = page_file_offset(page);
223                 kiocb.ki_left = PAGE_SIZE;
224                 kiocb.ki_nbytes = PAGE_SIZE;
225
226                 set_page_writeback(page);
227                 unlock_page(page);
228                 ret = mapping->a_ops->direct_IO(KERNEL_WRITE,
229                                                 &kiocb, &iov,
230                                                 kiocb.ki_pos, 1);
231                 kunmap(page);
232                 if (ret == PAGE_SIZE) {
233                         count_vm_event(PSWPOUT);
234                         ret = 0;
235                 } else {
236                         /*
237                          * In the case of swap-over-nfs, this can be a
238                          * temporary failure if the system has limited
239                          * memory for allocating transmit buffers.
240                          * Mark the page dirty and avoid
241                          * rotate_reclaimable_page but rate-limit the
242                          * messages but do not flag PageError like
243                          * the normal direct-to-bio case as it could
244                          * be temporary.
245                          */
246                         set_page_dirty(page);
247                         ClearPageReclaim(page);
248                         pr_err_ratelimited("Write error on dio swapfile (%Lu)\n",
249                                 page_file_offset(page));
250                 }
251                 end_page_writeback(page);
252                 return ret;
253         }
254
255         bio = get_swap_bio(GFP_NOIO, page, end_write_func);
256         if (bio == NULL) {
257                 set_page_dirty(page);
258                 unlock_page(page);
259                 ret = -ENOMEM;
260                 goto out;
261         }
262         if (wbc->sync_mode == WB_SYNC_ALL)
263                 rw |= REQ_SYNC;
264         count_vm_event(PSWPOUT);
265         set_page_writeback(page);
266         unlock_page(page);
267         submit_bio(rw, bio);
268 out:
269         return ret;
270 }
271
272 int swap_readpage(struct page *page)
273 {
274         struct bio *bio;
275         int ret = 0;
276         struct swap_info_struct *sis = page_swap_info(page);
277
278         VM_BUG_ON(!PageLocked(page));
279         VM_BUG_ON(PageUptodate(page));
280         if (frontswap_load(page) == 0) {
281                 SetPageUptodate(page);
282                 unlock_page(page);
283                 goto out;
284         }
285
286         if (sis->flags & SWP_FILE) {
287                 struct file *swap_file = sis->swap_file;
288                 struct address_space *mapping = swap_file->f_mapping;
289
290                 ret = mapping->a_ops->readpage(swap_file, page);
291                 if (!ret)
292                         count_vm_event(PSWPIN);
293                 return ret;
294         }
295
296         bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
297         if (bio == NULL) {
298                 unlock_page(page);
299                 ret = -ENOMEM;
300                 goto out;
301         }
302         count_vm_event(PSWPIN);
303         submit_bio(READ, bio);
304 out:
305         return ret;
306 }
307
308 int swap_set_page_dirty(struct page *page)
309 {
310         struct swap_info_struct *sis = page_swap_info(page);
311
312         if (sis->flags & SWP_FILE) {
313                 struct address_space *mapping = sis->swap_file->f_mapping;
314                 return mapping->a_ops->set_page_dirty(page);
315         } else {
316                 return __set_page_dirty_no_writeback(page);
317         }
318 }