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(gfp_t 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 /* 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) 61 * very quickly. 62 * 63 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 64 */ 65 set_page_dirty(page); 66 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n", 67 imajor(bio->bi_bdev->bd_inode), 68 iminor(bio->bi_bdev->bd_inode), 69 (unsigned long long)bio->bi_sector); 70 ClearPageReclaim(page); 71 } 72 end_page_writeback(page); 73 bio_put(bio); 74 return 0; 75 } 76 77 int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err) 78 { 79 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 80 struct page *page = bio->bi_io_vec[0].bv_page; 81 82 if (bio->bi_size) 83 return 1; 84 85 if (!uptodate) { 86 SetPageError(page); 87 ClearPageUptodate(page); 88 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n", 89 imajor(bio->bi_bdev->bd_inode), 90 iminor(bio->bi_bdev->bd_inode), 91 (unsigned long long)bio->bi_sector); 92 } else { 93 SetPageUptodate(page); 94 } 95 unlock_page(page); 96 bio_put(bio); 97 return 0; 98 } 99 100 /* 101 * We may have stale swap cache pages in memory: notice 102 * them here and get rid of the unnecessary final write. 103 */ 104 int swap_writepage(struct page *page, struct writeback_control *wbc) 105 { 106 struct bio *bio; 107 int ret = 0, rw = WRITE; 108 109 if (remove_exclusive_swap_page(page)) { 110 unlock_page(page); 111 goto out; 112 } 113 bio = get_swap_bio(GFP_NOIO, page_private(page), page, 114 end_swap_bio_write); 115 if (bio == NULL) { 116 set_page_dirty(page); 117 unlock_page(page); 118 ret = -ENOMEM; 119 goto out; 120 } 121 if (wbc->sync_mode == WB_SYNC_ALL) 122 rw |= (1 << BIO_RW_SYNC); 123 count_vm_event(PSWPOUT); 124 set_page_writeback(page); 125 unlock_page(page); 126 submit_bio(rw, bio); 127 out: 128 return ret; 129 } 130 131 int swap_readpage(struct file *file, struct page *page) 132 { 133 struct bio *bio; 134 int ret = 0; 135 136 BUG_ON(!PageLocked(page)); 137 ClearPageUptodate(page); 138 bio = get_swap_bio(GFP_KERNEL, page_private(page), page, 139 end_swap_bio_read); 140 if (bio == NULL) { 141 unlock_page(page); 142 ret = -ENOMEM; 143 goto out; 144 } 145 count_vm_event(PSWPIN); 146 submit_bio(READ, bio); 147 out: 148 return ret; 149 } 150 151 #ifdef CONFIG_SOFTWARE_SUSPEND 152 /* 153 * A scruffy utility function to read or write an arbitrary swap page 154 * and wait on the I/O. The caller must have a ref on the page. 155 * 156 * We use end_swap_bio_read() even for writes, because it happens to do what 157 * we want. 158 */ 159 int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page, 160 struct bio **bio_chain) 161 { 162 struct bio *bio; 163 int ret = 0; 164 int bio_rw; 165 166 lock_page(page); 167 168 bio = get_swap_bio(GFP_KERNEL, entry.val, page, end_swap_bio_read); 169 if (bio == NULL) { 170 unlock_page(page); 171 ret = -ENOMEM; 172 goto out; 173 } 174 175 bio_rw = rw; 176 if (!bio_chain) 177 bio_rw |= (1 << BIO_RW_SYNC); 178 if (bio_chain) 179 bio_get(bio); 180 submit_bio(bio_rw, bio); 181 if (bio_chain == NULL) { 182 wait_on_page_locked(page); 183 184 if (!PageUptodate(page) || PageError(page)) 185 ret = -EIO; 186 } 187 if (bio_chain) { 188 bio->bi_private = *bio_chain; 189 *bio_chain = bio; 190 } 191 out: 192 return ret; 193 } 194 #endif 195