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Linux/mm/page_io.c

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  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 
 25 static 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 
 45 static 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         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);
242 out:
243         return ret;
244 }
245 
246 int 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);
278 out:
279         return ret;
280 }
281 
282 int 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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