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/pagemap.h> 16 #include <linux/swap.h> 17 #include <linux/bio.h> 18 #include <linux/swapops.h> 19 #include <linux/writeback.h> 20 #include <asm/pgtable.h> 21 22 static struct bio *get_swap_bio(unsigned int __nocast gfp_flags, pgoff_t index, 23 struct page *page, bio_end_io_t end_io) 24 { 25 struct bio *bio; 26 27 bio = bio_alloc(gfp_flags, 1); 28 if (bio) { 29 struct swap_info_struct *sis; 30 swp_entry_t entry = { .val = index, }; 31 32 sis = get_swap_info_struct(swp_type(entry)); 33 bio->bi_sector = map_swap_page(sis, swp_offset(entry)) * 34 (PAGE_SIZE >> 9); 35 bio->bi_bdev = sis->bdev; 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_idx = 0; 41 bio->bi_size = PAGE_SIZE; 42 bio->bi_end_io = end_io; 43 } 44 return bio; 45 } 46 47 static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err) 48 { 49 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 50 struct page *page = bio->bi_io_vec[0].bv_page; 51 52 if (bio->bi_size) 53 return 1; 54 55 if (!uptodate) 56 SetPageError(page); 57 end_page_writeback(page); 58 bio_put(bio); 59 return 0; 60 } 61 62 static int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err) 63 { 64 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 65 struct page *page = bio->bi_io_vec[0].bv_page; 66 67 if (bio->bi_size) 68 return 1; 69 70 if (!uptodate) { 71 SetPageError(page); 72 ClearPageUptodate(page); 73 } else { 74 SetPageUptodate(page); 75 } 76 unlock_page(page); 77 bio_put(bio); 78 return 0; 79 } 80 81 /* 82 * We may have stale swap cache pages in memory: notice 83 * them here and get rid of the unnecessary final write. 84 */ 85 int swap_writepage(struct page *page, struct writeback_control *wbc) 86 { 87 struct bio *bio; 88 int ret = 0, rw = WRITE; 89 90 if (remove_exclusive_swap_page(page)) { 91 unlock_page(page); 92 goto out; 93 } 94 bio = get_swap_bio(GFP_NOIO, page->private, page, end_swap_bio_write); 95 if (bio == NULL) { 96 set_page_dirty(page); 97 unlock_page(page); 98 ret = -ENOMEM; 99 goto out; 100 } 101 if (wbc->sync_mode == WB_SYNC_ALL) 102 rw |= (1 << BIO_RW_SYNC); 103 inc_page_state(pswpout); 104 set_page_writeback(page); 105 unlock_page(page); 106 submit_bio(rw, bio); 107 out: 108 return ret; 109 } 110 111 int swap_readpage(struct file *file, struct page *page) 112 { 113 struct bio *bio; 114 int ret = 0; 115 116 BUG_ON(!PageLocked(page)); 117 ClearPageUptodate(page); 118 bio = get_swap_bio(GFP_KERNEL, page->private, page, end_swap_bio_read); 119 if (bio == NULL) { 120 unlock_page(page); 121 ret = -ENOMEM; 122 goto out; 123 } 124 inc_page_state(pswpin); 125 submit_bio(READ, bio); 126 out: 127 return ret; 128 } 129 130 #if defined(CONFIG_SOFTWARE_SUSPEND) || defined(CONFIG_PM_DISK) 131 /* 132 * A scruffy utility function to read or write an arbitrary swap page 133 * and wait on the I/O. The caller must have a ref on the page. 134 * 135 * We use end_swap_bio_read() even for writes, because it happens to do what 136 * we want. 137 */ 138 int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page) 139 { 140 struct bio *bio; 141 int ret = 0; 142 143 lock_page(page); 144 145 bio = get_swap_bio(GFP_KERNEL, entry.val, page, end_swap_bio_read); 146 if (bio == NULL) { 147 unlock_page(page); 148 ret = -ENOMEM; 149 goto out; 150 } 151 152 submit_bio(rw | (1 << BIO_RW_SYNC), bio); 153 wait_on_page_locked(page); 154 155 if (!PageUptodate(page) || PageError(page)) 156 ret = -EIO; 157 out: 158 return ret; 159 } 160 #endif 161