4 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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
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>
27 static struct bio
*get_swap_bio(gfp_t gfp_flags
,
28 struct page
*page
, bio_end_io_t end_io
)
32 bio
= bio_alloc(gfp_flags
, 1);
34 bio
->bi_sector
= map_swap_page(page
, &bio
->bi_bdev
);
35 bio
->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;
40 bio
->bi_size
= PAGE_SIZE
;
41 bio
->bi_end_io
= end_io
;
46 void end_swap_bio_write(struct bio
*bio
, int err
)
48 const int uptodate
= test_bit(BIO_UPTODATE
, &bio
->bi_flags
);
49 struct page
*page
= bio
->bi_io_vec
[0].bv_page
;
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)
59 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
63 printk(KERN_ALERT
"Write-error on swap-device (%u:%u:%Lu)\n",
64 imajor(bio
->bi_bdev
->bd_inode
),
65 iminor(bio
->bi_bdev
->bd_inode
),
66 (unsigned long long)bio
->bi_sector
);
68 ClearPageReclaim(page
);
70 end_page_writeback(page
);
74 void end_swap_bio_read(struct bio
*bio
, int err
)
76 const int uptodate
= test_bit(BIO_UPTODATE
, &bio
->bi_flags
);
77 struct page
*page
= bio
->bi_io_vec
[0].bv_page
;
81 ClearPageUptodate(page
);
82 printk(KERN_ALERT
"Read-error on swap-device (%u:%u:%Lu)\n",
83 imajor(bio
->bi_bdev
->bd_inode
),
84 iminor(bio
->bi_bdev
->bd_inode
),
85 (unsigned long long)bio
->bi_sector
);
89 SetPageUptodate(page
);
92 * There is no guarantee that the page is in swap cache - the software
93 * suspend code (at least) uses end_swap_bio_read() against a non-
94 * swapcache page. So we must check PG_swapcache before proceeding with
97 if (likely(PageSwapCache(page
))) {
98 struct swap_info_struct
*sis
;
100 sis
= page_swap_info(page
);
101 if (sis
->flags
& SWP_BLKDEV
) {
103 * The swap subsystem performs lazy swap slot freeing,
104 * expecting that the page will be swapped out again.
105 * So we can avoid an unnecessary write if the page
107 * This is good for real swap storage because we can
108 * reduce unnecessary I/O and enhance wear-leveling
109 * if an SSD is used as the as swap device.
110 * But if in-memory swap device (eg zram) is used,
111 * this causes a duplicated copy between uncompressed
112 * data in VM-owned memory and compressed data in
113 * zram-owned memory. So let's free zram-owned memory
114 * and make the VM-owned decompressed page *dirty*,
115 * so the page should be swapped out somewhere again if
116 * we again wish to reclaim it.
118 struct gendisk
*disk
= sis
->bdev
->bd_disk
;
119 if (disk
->fops
->swap_slot_free_notify
) {
121 unsigned long offset
;
123 entry
.val
= page_private(page
);
124 offset
= swp_offset(entry
);
127 disk
->fops
->swap_slot_free_notify(sis
->bdev
,
138 int generic_swapfile_activate(struct swap_info_struct
*sis
,
139 struct file
*swap_file
,
142 struct address_space
*mapping
= swap_file
->f_mapping
;
143 struct inode
*inode
= mapping
->host
;
144 unsigned blocks_per_page
;
145 unsigned long page_no
;
147 sector_t probe_block
;
149 sector_t lowest_block
= -1;
150 sector_t highest_block
= 0;
154 blkbits
= inode
->i_blkbits
;
155 blocks_per_page
= PAGE_SIZE
>> blkbits
;
158 * Map all the blocks into the extent list. This code doesn't try
163 last_block
= i_size_read(inode
) >> blkbits
;
164 while ((probe_block
+ blocks_per_page
) <= last_block
&&
165 page_no
< sis
->max
) {
166 unsigned block_in_page
;
167 sector_t first_block
;
169 first_block
= bmap(inode
, probe_block
);
170 if (first_block
== 0)
174 * It must be PAGE_SIZE aligned on-disk
176 if (first_block
& (blocks_per_page
- 1)) {
181 for (block_in_page
= 1; block_in_page
< blocks_per_page
;
185 block
= bmap(inode
, probe_block
+ block_in_page
);
188 if (block
!= first_block
+ block_in_page
) {
195 first_block
>>= (PAGE_SHIFT
- blkbits
);
196 if (page_no
) { /* exclude the header page */
197 if (first_block
< lowest_block
)
198 lowest_block
= first_block
;
199 if (first_block
> highest_block
)
200 highest_block
= first_block
;
204 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
206 ret
= add_swap_extent(sis
, page_no
, 1, first_block
);
211 probe_block
+= blocks_per_page
;
216 *span
= 1 + highest_block
- lowest_block
;
218 page_no
= 1; /* force Empty message */
220 sis
->pages
= page_no
- 1;
221 sis
->highest_bit
= page_no
- 1;
225 printk(KERN_ERR
"swapon: swapfile has holes\n");
231 * We may have stale swap cache pages in memory: notice
232 * them here and get rid of the unnecessary final write.
234 int swap_writepage(struct page
*page
, struct writeback_control
*wbc
)
238 if (try_to_free_swap(page
)) {
242 if (frontswap_store(page
) == 0) {
243 set_page_writeback(page
);
245 end_page_writeback(page
);
248 ret
= __swap_writepage(page
, wbc
, end_swap_bio_write
);
253 int __swap_writepage(struct page
*page
, struct writeback_control
*wbc
,
254 void (*end_write_func
)(struct bio
*, int))
257 int ret
= 0, rw
= WRITE
;
258 struct swap_info_struct
*sis
= page_swap_info(page
);
260 if (sis
->flags
& SWP_FILE
) {
262 struct file
*swap_file
= sis
->swap_file
;
263 struct address_space
*mapping
= swap_file
->f_mapping
;
265 .iov_base
= kmap(page
),
266 .iov_len
= PAGE_SIZE
,
269 init_sync_kiocb(&kiocb
, swap_file
);
270 kiocb
.ki_pos
= page_file_offset(page
);
271 kiocb
.ki_left
= PAGE_SIZE
;
272 kiocb
.ki_nbytes
= PAGE_SIZE
;
274 set_page_writeback(page
);
276 ret
= mapping
->a_ops
->direct_IO(KERNEL_WRITE
,
280 if (ret
== PAGE_SIZE
) {
281 count_vm_event(PSWPOUT
);
285 * In the case of swap-over-nfs, this can be a
286 * temporary failure if the system has limited
287 * memory for allocating transmit buffers.
288 * Mark the page dirty and avoid
289 * rotate_reclaimable_page but rate-limit the
290 * messages but do not flag PageError like
291 * the normal direct-to-bio case as it could
294 set_page_dirty(page
);
295 ClearPageReclaim(page
);
296 pr_err_ratelimited("Write error on dio swapfile (%Lu)\n",
297 page_file_offset(page
));
299 end_page_writeback(page
);
303 bio
= get_swap_bio(GFP_NOIO
, page
, end_write_func
);
305 set_page_dirty(page
);
310 if (wbc
->sync_mode
== WB_SYNC_ALL
)
312 count_vm_event(PSWPOUT
);
313 set_page_writeback(page
);
320 int swap_readpage(struct page
*page
)
324 struct swap_info_struct
*sis
= page_swap_info(page
);
326 VM_BUG_ON(!PageLocked(page
));
327 VM_BUG_ON(PageUptodate(page
));
328 if (frontswap_load(page
) == 0) {
329 SetPageUptodate(page
);
334 if (sis
->flags
& SWP_FILE
) {
335 struct file
*swap_file
= sis
->swap_file
;
336 struct address_space
*mapping
= swap_file
->f_mapping
;
338 ret
= mapping
->a_ops
->readpage(swap_file
, page
);
340 count_vm_event(PSWPIN
);
344 bio
= get_swap_bio(GFP_KERNEL
, page
, end_swap_bio_read
);
350 count_vm_event(PSWPIN
);
351 submit_bio(READ
, bio
);
356 int swap_set_page_dirty(struct page
*page
)
358 struct swap_info_struct
*sis
= page_swap_info(page
);
360 if (sis
->flags
& SWP_FILE
) {
361 struct address_space
*mapping
= sis
->swap_file
->f_mapping
;
362 return mapping
->a_ops
->set_page_dirty(page
);
364 return __set_page_dirty_no_writeback(page
);