Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/jkirsher/net...
[pandora-kernel.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 <linux/blkdev.h>
25 #include <asm/pgtable.h>
26
27 static struct bio *get_swap_bio(gfp_t gfp_flags,
28                                 struct page *page, bio_end_io_t end_io)
29 {
30         struct bio *bio;
31
32         bio = bio_alloc(gfp_flags, 1);
33         if (bio) {
34                 bio->bi_iter.bi_sector = map_swap_page(page, &bio->bi_bdev);
35                 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
36                 bio->bi_io_vec[0].bv_page = page;
37                 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
38                 bio->bi_io_vec[0].bv_offset = 0;
39                 bio->bi_vcnt = 1;
40                 bio->bi_iter.bi_size = PAGE_SIZE;
41                 bio->bi_end_io = end_io;
42         }
43         return bio;
44 }
45
46 void end_swap_bio_write(struct bio *bio, int err)
47 {
48         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
49         struct page *page = bio->bi_io_vec[0].bv_page;
50
51         if (!uptodate) {
52                 SetPageError(page);
53                 /*
54                  * We failed to write the page out to swap-space.
55                  * Re-dirty the page in order to avoid it being reclaimed.
56                  * Also print a dire warning that things will go BAD (tm)
57                  * very quickly.
58                  *
59                  * Also clear PG_reclaim to avoid rotate_reclaimable_page()
60                  */
61                 set_page_dirty(page);
62                 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
63                                 imajor(bio->bi_bdev->bd_inode),
64                                 iminor(bio->bi_bdev->bd_inode),
65                                 (unsigned long long)bio->bi_iter.bi_sector);
66                 ClearPageReclaim(page);
67         }
68         end_page_writeback(page);
69         bio_put(bio);
70 }
71
72 void end_swap_bio_read(struct bio *bio, int err)
73 {
74         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
75         struct page *page = bio->bi_io_vec[0].bv_page;
76
77         if (!uptodate) {
78                 SetPageError(page);
79                 ClearPageUptodate(page);
80                 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
81                                 imajor(bio->bi_bdev->bd_inode),
82                                 iminor(bio->bi_bdev->bd_inode),
83                                 (unsigned long long)bio->bi_iter.bi_sector);
84                 goto out;
85         }
86
87         SetPageUptodate(page);
88
89         /*
90          * There is no guarantee that the page is in swap cache - the software
91          * suspend code (at least) uses end_swap_bio_read() against a non-
92          * swapcache page.  So we must check PG_swapcache before proceeding with
93          * this optimization.
94          */
95         if (likely(PageSwapCache(page))) {
96                 struct swap_info_struct *sis;
97
98                 sis = page_swap_info(page);
99                 if (sis->flags & SWP_BLKDEV) {
100                         /*
101                          * The swap subsystem performs lazy swap slot freeing,
102                          * expecting that the page will be swapped out again.
103                          * So we can avoid an unnecessary write if the page
104                          * isn't redirtied.
105                          * This is good for real swap storage because we can
106                          * reduce unnecessary I/O and enhance wear-leveling
107                          * if an SSD is used as the as swap device.
108                          * But if in-memory swap device (eg zram) is used,
109                          * this causes a duplicated copy between uncompressed
110                          * data in VM-owned memory and compressed data in
111                          * zram-owned memory.  So let's free zram-owned memory
112                          * and make the VM-owned decompressed page *dirty*,
113                          * so the page should be swapped out somewhere again if
114                          * we again wish to reclaim it.
115                          */
116                         struct gendisk *disk = sis->bdev->bd_disk;
117                         if (disk->fops->swap_slot_free_notify) {
118                                 swp_entry_t entry;
119                                 unsigned long offset;
120
121                                 entry.val = page_private(page);
122                                 offset = swp_offset(entry);
123
124                                 SetPageDirty(page);
125                                 disk->fops->swap_slot_free_notify(sis->bdev,
126                                                 offset);
127                         }
128                 }
129         }
130
131 out:
132         unlock_page(page);
133         bio_put(bio);
134 }
135
136 int generic_swapfile_activate(struct swap_info_struct *sis,
137                                 struct file *swap_file,
138                                 sector_t *span)
139 {
140         struct address_space *mapping = swap_file->f_mapping;
141         struct inode *inode = mapping->host;
142         unsigned blocks_per_page;
143         unsigned long page_no;
144         unsigned blkbits;
145         sector_t probe_block;
146         sector_t last_block;
147         sector_t lowest_block = -1;
148         sector_t highest_block = 0;
149         int nr_extents = 0;
150         int ret;
151
152         blkbits = inode->i_blkbits;
153         blocks_per_page = PAGE_SIZE >> blkbits;
154
155         /*
156          * Map all the blocks into the extent list.  This code doesn't try
157          * to be very smart.
158          */
159         probe_block = 0;
160         page_no = 0;
161         last_block = i_size_read(inode) >> blkbits;
162         while ((probe_block + blocks_per_page) <= last_block &&
163                         page_no < sis->max) {
164                 unsigned block_in_page;
165                 sector_t first_block;
166
167                 first_block = bmap(inode, probe_block);
168                 if (first_block == 0)
169                         goto bad_bmap;
170
171                 /*
172                  * It must be PAGE_SIZE aligned on-disk
173                  */
174                 if (first_block & (blocks_per_page - 1)) {
175                         probe_block++;
176                         goto reprobe;
177                 }
178
179                 for (block_in_page = 1; block_in_page < blocks_per_page;
180                                         block_in_page++) {
181                         sector_t block;
182
183                         block = bmap(inode, probe_block + block_in_page);
184                         if (block == 0)
185                                 goto bad_bmap;
186                         if (block != first_block + block_in_page) {
187                                 /* Discontiguity */
188                                 probe_block++;
189                                 goto reprobe;
190                         }
191                 }
192
193                 first_block >>= (PAGE_SHIFT - blkbits);
194                 if (page_no) {  /* exclude the header page */
195                         if (first_block < lowest_block)
196                                 lowest_block = first_block;
197                         if (first_block > highest_block)
198                                 highest_block = first_block;
199                 }
200
201                 /*
202                  * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
203                  */
204                 ret = add_swap_extent(sis, page_no, 1, first_block);
205                 if (ret < 0)
206                         goto out;
207                 nr_extents += ret;
208                 page_no++;
209                 probe_block += blocks_per_page;
210 reprobe:
211                 continue;
212         }
213         ret = nr_extents;
214         *span = 1 + highest_block - lowest_block;
215         if (page_no == 0)
216                 page_no = 1;    /* force Empty message */
217         sis->max = page_no;
218         sis->pages = page_no - 1;
219         sis->highest_bit = page_no - 1;
220 out:
221         return ret;
222 bad_bmap:
223         printk(KERN_ERR "swapon: swapfile has holes\n");
224         ret = -EINVAL;
225         goto out;
226 }
227
228 /*
229  * We may have stale swap cache pages in memory: notice
230  * them here and get rid of the unnecessary final write.
231  */
232 int swap_writepage(struct page *page, struct writeback_control *wbc)
233 {
234         int ret = 0;
235
236         if (try_to_free_swap(page)) {
237                 unlock_page(page);
238                 goto out;
239         }
240         if (frontswap_store(page) == 0) {
241                 set_page_writeback(page);
242                 unlock_page(page);
243                 end_page_writeback(page);
244                 goto out;
245         }
246         ret = __swap_writepage(page, wbc, end_swap_bio_write);
247 out:
248         return ret;
249 }
250
251 static sector_t swap_page_sector(struct page *page)
252 {
253         return (sector_t)__page_file_index(page) << (PAGE_CACHE_SHIFT - 9);
254 }
255
256 int __swap_writepage(struct page *page, struct writeback_control *wbc,
257         void (*end_write_func)(struct bio *, int))
258 {
259         struct bio *bio;
260         int ret, rw = WRITE;
261         struct swap_info_struct *sis = page_swap_info(page);
262
263         if (sis->flags & SWP_FILE) {
264                 struct kiocb kiocb;
265                 struct file *swap_file = sis->swap_file;
266                 struct address_space *mapping = swap_file->f_mapping;
267                 struct bio_vec bv = {
268                         .bv_page = page,
269                         .bv_len  = PAGE_SIZE,
270                         .bv_offset = 0
271                 };
272                 struct iov_iter from = {
273                         .type = ITER_BVEC | WRITE,
274                         .count = PAGE_SIZE,
275                         .iov_offset = 0,
276                         .nr_segs = 1,
277                 };
278                 from.bvec = &bv;        /* older gcc versions are broken */
279
280                 init_sync_kiocb(&kiocb, swap_file);
281                 kiocb.ki_pos = page_file_offset(page);
282                 kiocb.ki_nbytes = PAGE_SIZE;
283
284                 set_page_writeback(page);
285                 unlock_page(page);
286                 ret = mapping->a_ops->direct_IO(ITER_BVEC | WRITE,
287                                                 &kiocb, &from,
288                                                 kiocb.ki_pos);
289                 if (ret == PAGE_SIZE) {
290                         count_vm_event(PSWPOUT);
291                         ret = 0;
292                 } else {
293                         /*
294                          * In the case of swap-over-nfs, this can be a
295                          * temporary failure if the system has limited
296                          * memory for allocating transmit buffers.
297                          * Mark the page dirty and avoid
298                          * rotate_reclaimable_page but rate-limit the
299                          * messages but do not flag PageError like
300                          * the normal direct-to-bio case as it could
301                          * be temporary.
302                          */
303                         set_page_dirty(page);
304                         ClearPageReclaim(page);
305                         pr_err_ratelimited("Write error on dio swapfile (%Lu)\n",
306                                 page_file_offset(page));
307                 }
308                 end_page_writeback(page);
309                 return ret;
310         }
311
312         ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
313         if (!ret) {
314                 count_vm_event(PSWPOUT);
315                 return 0;
316         }
317
318         ret = 0;
319         bio = get_swap_bio(GFP_NOIO, page, end_write_func);
320         if (bio == NULL) {
321                 set_page_dirty(page);
322                 unlock_page(page);
323                 ret = -ENOMEM;
324                 goto out;
325         }
326         if (wbc->sync_mode == WB_SYNC_ALL)
327                 rw |= REQ_SYNC;
328         count_vm_event(PSWPOUT);
329         set_page_writeback(page);
330         unlock_page(page);
331         submit_bio(rw, bio);
332 out:
333         return ret;
334 }
335
336 int swap_readpage(struct page *page)
337 {
338         struct bio *bio;
339         int ret = 0;
340         struct swap_info_struct *sis = page_swap_info(page);
341
342         VM_BUG_ON_PAGE(!PageLocked(page), page);
343         VM_BUG_ON_PAGE(PageUptodate(page), page);
344         if (frontswap_load(page) == 0) {
345                 SetPageUptodate(page);
346                 unlock_page(page);
347                 goto out;
348         }
349
350         if (sis->flags & SWP_FILE) {
351                 struct file *swap_file = sis->swap_file;
352                 struct address_space *mapping = swap_file->f_mapping;
353
354                 ret = mapping->a_ops->readpage(swap_file, page);
355                 if (!ret)
356                         count_vm_event(PSWPIN);
357                 return ret;
358         }
359
360         ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
361         if (!ret) {
362                 count_vm_event(PSWPIN);
363                 return 0;
364         }
365
366         ret = 0;
367         bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
368         if (bio == NULL) {
369                 unlock_page(page);
370                 ret = -ENOMEM;
371                 goto out;
372         }
373         count_vm_event(PSWPIN);
374         submit_bio(READ, bio);
375 out:
376         return ret;
377 }
378
379 int swap_set_page_dirty(struct page *page)
380 {
381         struct swap_info_struct *sis = page_swap_info(page);
382
383         if (sis->flags & SWP_FILE) {
384                 struct address_space *mapping = sis->swap_file->f_mapping;
385                 return mapping->a_ops->set_page_dirty(page);
386         } else {
387                 return __set_page_dirty_no_writeback(page);
388         }
389 }