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 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), page, 95 end_swap_bio_write); 96 if (bio == NULL) { 97 set_page_dirty(page); 98 unlock_page(page); 99 ret = -ENOMEM; 100 goto out; 101 } 102 if (wbc->sync_mode == WB_SYNC_ALL) 103 rw |= (1 << BIO_RW_SYNC); 104 inc_page_state(pswpout); 105 set_page_writeback(page); 106 unlock_page(page); 107 submit_bio(rw, bio); 108 out: 109 return ret; 110 } 111 112 int swap_readpage(struct file *file, struct page *page) 113 { 114 struct bio *bio; 115 int ret = 0; 116 117 BUG_ON(!PageLocked(page)); 118 ClearPageUptodate(page); 119 bio = get_swap_bio(GFP_KERNEL, page_private(page), page, 120 end_swap_bio_read); 121 if (bio == NULL) { 122 unlock_page(page); 123 ret = -ENOMEM; 124 goto out; 125 } 126 inc_page_state(pswpin); 127 submit_bio(READ, bio); 128 out: 129 return ret; 130 } 131 132 #ifdef CONFIG_SOFTWARE_SUSPEND 133 /* 134 * A scruffy utility function to read or write an arbitrary swap page 135 * and wait on the I/O. The caller must have a ref on the page. 136 * 137 * We use end_swap_bio_read() even for writes, because it happens to do what 138 * we want. 139 */ 140 int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page) 141 { 142 struct bio *bio; 143 int ret = 0; 144 145 lock_page(page); 146 147 bio = get_swap_bio(GFP_KERNEL, entry.val, page, end_swap_bio_read); 148 if (bio == NULL) { 149 unlock_page(page); 150 ret = -ENOMEM; 151 goto out; 152 } 153 154 submit_bio(rw | (1 << BIO_RW_SYNC), bio); 155 wait_on_page_locked(page); 156 157 if (!PageUptodate(page) || PageError(page)) 158 ret = -EIO; 159 out: 160 return ret; 161 } 162 #endif 163