1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
7 * Swap reorganised 29.12.95,
8 * Asynchronous swapping added 30.12.95. Stephen Tweedie
9 * Removed race in async swapping. 14.4.1996. Bruno Haible
10 * Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
11 * Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
15 #include <linux/kernel_stat.h>
16 #include <linux/gfp.h>
17 #include <linux/pagemap.h>
18 #include <linux/swap.h>
19 #include <linux/bio.h>
20 #include <linux/swapops.h>
21 #include <linux/buffer_head.h>
22 #include <linux/writeback.h>
23 #include <linux/frontswap.h>
24 #include <linux/blkdev.h>
25 #include <linux/uio.h>
26 #include <linux/sched/task.h>
27 #include <asm/pgtable.h>
29 static struct bio *get_swap_bio(gfp_t gfp_flags,
30 struct page *page, bio_end_io_t end_io)
32 int i, nr = hpage_nr_pages(page);
35 bio = bio_alloc(gfp_flags, nr);
37 struct block_device *bdev;
39 bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
40 bio_set_dev(bio, bdev);
41 bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
42 bio->bi_end_io = end_io;
44 for (i = 0; i < nr; i++)
45 bio_add_page(bio, page + i, PAGE_SIZE, 0);
46 VM_BUG_ON(bio->bi_iter.bi_size != PAGE_SIZE * nr);
51 void end_swap_bio_write(struct bio *bio)
53 struct page *page = bio_first_page_all(bio);
58 * We failed to write the page out to swap-space.
59 * Re-dirty the page in order to avoid it being reclaimed.
60 * Also print a dire warning that things will go BAD (tm)
63 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
66 pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
67 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
68 (unsigned long long)bio->bi_iter.bi_sector);
69 ClearPageReclaim(page);
71 end_page_writeback(page);
75 static void swap_slot_free_notify(struct page *page)
77 struct swap_info_struct *sis;
82 * There is no guarantee that the page is in swap cache - the software
83 * suspend code (at least) uses end_swap_bio_read() against a non-
84 * swapcache page. So we must check PG_swapcache before proceeding with
87 if (unlikely(!PageSwapCache(page)))
90 sis = page_swap_info(page);
91 if (!(sis->flags & SWP_BLKDEV))
95 * The swap subsystem performs lazy swap slot freeing,
96 * expecting that the page will be swapped out again.
97 * So we can avoid an unnecessary write if the page
99 * This is good for real swap storage because we can
100 * reduce unnecessary I/O and enhance wear-leveling
101 * if an SSD is used as the as swap device.
102 * But if in-memory swap device (eg zram) is used,
103 * this causes a duplicated copy between uncompressed
104 * data in VM-owned memory and compressed data in
105 * zram-owned memory. So let's free zram-owned memory
106 * and make the VM-owned decompressed page *dirty*,
107 * so the page should be swapped out somewhere again if
108 * we again wish to reclaim it.
110 disk = sis->bdev->bd_disk;
111 entry.val = page_private(page);
112 if (disk->fops->swap_slot_free_notify &&
113 __swap_count(sis, entry) == 1) {
114 unsigned long offset;
116 offset = swp_offset(entry);
119 disk->fops->swap_slot_free_notify(sis->bdev,
124 static void end_swap_bio_read(struct bio *bio)
126 struct page *page = bio_first_page_all(bio);
127 struct task_struct *waiter = bio->bi_private;
129 if (bio->bi_status) {
131 ClearPageUptodate(page);
132 pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
133 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
134 (unsigned long long)bio->bi_iter.bi_sector);
138 SetPageUptodate(page);
139 swap_slot_free_notify(page);
142 WRITE_ONCE(bio->bi_private, NULL);
144 wake_up_process(waiter);
145 put_task_struct(waiter);
148 int generic_swapfile_activate(struct swap_info_struct *sis,
149 struct file *swap_file,
152 struct address_space *mapping = swap_file->f_mapping;
153 struct inode *inode = mapping->host;
154 unsigned blocks_per_page;
155 unsigned long page_no;
157 sector_t probe_block;
159 sector_t lowest_block = -1;
160 sector_t highest_block = 0;
164 blkbits = inode->i_blkbits;
165 blocks_per_page = PAGE_SIZE >> blkbits;
168 * Map all the blocks into the extent list. This code doesn't try
173 last_block = i_size_read(inode) >> blkbits;
174 while ((probe_block + blocks_per_page) <= last_block &&
175 page_no < sis->max) {
176 unsigned block_in_page;
177 sector_t first_block;
181 first_block = bmap(inode, probe_block);
182 if (first_block == 0)
186 * It must be PAGE_SIZE aligned on-disk
188 if (first_block & (blocks_per_page - 1)) {
193 for (block_in_page = 1; block_in_page < blocks_per_page;
197 block = bmap(inode, probe_block + block_in_page);
200 if (block != first_block + block_in_page) {
207 first_block >>= (PAGE_SHIFT - blkbits);
208 if (page_no) { /* exclude the header page */
209 if (first_block < lowest_block)
210 lowest_block = first_block;
211 if (first_block > highest_block)
212 highest_block = first_block;
216 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
218 ret = add_swap_extent(sis, page_no, 1, first_block);
223 probe_block += blocks_per_page;
228 *span = 1 + highest_block - lowest_block;
230 page_no = 1; /* force Empty message */
232 sis->pages = page_no - 1;
233 sis->highest_bit = page_no - 1;
237 pr_err("swapon: swapfile has holes\n");
243 * We may have stale swap cache pages in memory: notice
244 * them here and get rid of the unnecessary final write.
246 int swap_writepage(struct page *page, struct writeback_control *wbc)
250 if (try_to_free_swap(page)) {
254 if (frontswap_store(page) == 0) {
255 set_page_writeback(page);
257 end_page_writeback(page);
260 ret = __swap_writepage(page, wbc, end_swap_bio_write);
265 static sector_t swap_page_sector(struct page *page)
267 return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
270 static inline void count_swpout_vm_event(struct page *page)
272 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
273 if (unlikely(PageTransHuge(page)))
274 count_vm_event(THP_SWPOUT);
276 count_vm_events(PSWPOUT, hpage_nr_pages(page));
279 int __swap_writepage(struct page *page, struct writeback_control *wbc,
280 bio_end_io_t end_write_func)
284 struct swap_info_struct *sis = page_swap_info(page);
286 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
287 if (sis->flags & SWP_FILE) {
289 struct file *swap_file = sis->swap_file;
290 struct address_space *mapping = swap_file->f_mapping;
291 struct bio_vec bv = {
296 struct iov_iter from;
298 iov_iter_bvec(&from, ITER_BVEC | WRITE, &bv, 1, PAGE_SIZE);
299 init_sync_kiocb(&kiocb, swap_file);
300 kiocb.ki_pos = page_file_offset(page);
302 set_page_writeback(page);
304 ret = mapping->a_ops->direct_IO(&kiocb, &from);
305 if (ret == PAGE_SIZE) {
306 count_vm_event(PSWPOUT);
310 * In the case of swap-over-nfs, this can be a
311 * temporary failure if the system has limited
312 * memory for allocating transmit buffers.
313 * Mark the page dirty and avoid
314 * rotate_reclaimable_page but rate-limit the
315 * messages but do not flag PageError like
316 * the normal direct-to-bio case as it could
319 set_page_dirty(page);
320 ClearPageReclaim(page);
321 pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
322 page_file_offset(page));
324 end_page_writeback(page);
328 ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
330 count_swpout_vm_event(page);
335 bio = get_swap_bio(GFP_NOIO, page, end_write_func);
337 set_page_dirty(page);
342 bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
343 bio_associate_blkcg_from_page(bio, page);
344 count_swpout_vm_event(page);
345 set_page_writeback(page);
352 int swap_readpage(struct page *page, bool synchronous)
356 struct swap_info_struct *sis = page_swap_info(page);
358 struct gendisk *disk;
360 VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
361 VM_BUG_ON_PAGE(!PageLocked(page), page);
362 VM_BUG_ON_PAGE(PageUptodate(page), page);
363 if (frontswap_load(page) == 0) {
364 SetPageUptodate(page);
369 if (sis->flags & SWP_FILE) {
370 struct file *swap_file = sis->swap_file;
371 struct address_space *mapping = swap_file->f_mapping;
373 ret = mapping->a_ops->readpage(swap_file, page);
375 count_vm_event(PSWPIN);
379 ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
381 if (trylock_page(page)) {
382 swap_slot_free_notify(page);
386 count_vm_event(PSWPIN);
391 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
399 * Keep this task valid during swap readpage because the oom killer may
400 * attempt to access it in the page fault retry time check.
402 get_task_struct(current);
403 bio->bi_private = current;
404 bio_set_op_attrs(bio, REQ_OP_READ, 0);
405 count_vm_event(PSWPIN);
407 qc = submit_bio(bio);
408 while (synchronous) {
409 set_current_state(TASK_UNINTERRUPTIBLE);
410 if (!READ_ONCE(bio->bi_private))
413 if (!blk_poll(disk->queue, qc))
416 __set_current_state(TASK_RUNNING);
423 int swap_set_page_dirty(struct page *page)
425 struct swap_info_struct *sis = page_swap_info(page);
427 if (sis->flags & SWP_FILE) {
428 struct address_space *mapping = sis->swap_file->f_mapping;
430 VM_BUG_ON_PAGE(!PageSwapCache(page), page);
431 return mapping->a_ops->set_page_dirty(page);
433 return __set_page_dirty_no_writeback(page);