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/pagemap.h>
16 #include <linux/swap.h>
17 #include <linux/bio.h>
18 #include <linux/swapops.h>
19 #include <linux/buffer_head.h> /* for block_sync_page() */
20 #include <linux/mpage.h>
21 #include <linux/writeback.h>
22 #include <asm/pgtable.h>
25 get_swap_bio(int gfp_flags, struct page *page, bio_end_io_t end_io)
29 bio = bio_alloc(gfp_flags, 1);
31 struct swap_info_struct *sis;
34 BUG_ON(!PageSwapCache(page));
35 entry.val = page->private;
36 sis = get_swap_info_struct(swp_type(entry));
38 bio->bi_sector = map_swap_page(sis, swp_offset(entry)) *
40 bio->bi_bdev = sis->bdev;
41 bio->bi_io_vec[0].bv_page = page;
42 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
43 bio->bi_io_vec[0].bv_offset = 0;
46 bio->bi_size = PAGE_SIZE;
47 bio->bi_end_io = end_io;
52 static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err)
54 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
55 struct page *page = bio->bi_io_vec[0].bv_page;
62 end_page_writeback(page);
67 static int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
69 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
70 struct page *page = bio->bi_io_vec[0].bv_page;
77 ClearPageUptodate(page);
79 SetPageUptodate(page);
87 * We may have stale swap cache pages in memory: notice
88 * them here and get rid of the unnecessary final write.
90 int swap_writepage(struct page *page, struct writeback_control *wbc)
95 if (remove_exclusive_swap_page(page)) {
99 bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
101 set_page_dirty(page);
106 inc_page_state(pswpout);
107 set_page_writeback(page);
109 submit_bio(WRITE, bio);
114 int swap_readpage(struct file *file, struct page *page)
119 BUG_ON(!PageLocked(page));
120 ClearPageUptodate(page);
121 bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
127 inc_page_state(pswpin);
128 submit_bio(READ, bio);
133 struct address_space_operations swap_aops = {
134 .writepage = swap_writepage,
135 .readpage = swap_readpage,
136 .sync_page = block_sync_page,
137 .set_page_dirty = __set_page_dirty_nobuffers,
141 * A scruffy utility function to read or write an arbitrary swap page
142 * and wait on the I/O.
144 int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page)
147 struct writeback_control swap_wbc = {
148 .sync_mode = WB_SYNC_ALL,
153 BUG_ON(page_mapping(page));
154 SetPageSwapCache(page);
155 page->private = entry.val;
158 ret = swap_readpage(NULL, page);
159 wait_on_page_locked(page);
161 ret = swap_writepage(page, &swap_wbc);
162 wait_on_page_writeback(page);
164 ClearPageSwapCache(page);
165 if (ret == 0 && (!PageUptodate(page) || PageError(page)))