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 void end_swap_bio_write(struct bio *bio, 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 (!uptodate) { 53 SetPageError(page); 54 /* 55 * We failed to write the page out to swap-space. 56 * Re-dirty the page in order to avoid it being reclaimed. 57 * Also print a dire warning that things will go BAD (tm) 58 * very quickly. 59 * 60 * Also clear PG_reclaim to avoid rotate_reclaimable_page() 61 */ 62 set_page_dirty(page); 63 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n", 64 imajor(bio->bi_bdev->bd_inode), 65 iminor(bio->bi_bdev->bd_inode), 66 (unsigned long long)bio->bi_sector); 67 ClearPageReclaim(page); 68 } 69 end_page_writeback(page); 70 bio_put(bio); 71 } 72 73 void end_swap_bio_read(struct bio *bio, int err) 74 { 75 const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); 76 struct page *page = bio->bi_io_vec[0].bv_page; 77 78 if (!uptodate) { 79 SetPageError(page); 80 ClearPageUptodate(page); 81 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n", 82 imajor(bio->bi_bdev->bd_inode), 83 iminor(bio->bi_bdev->bd_inode), 84 (unsigned long long)bio->bi_sector); 85 } else { 86 SetPageUptodate(page); 87 } 88 unlock_page(page); 89 bio_put(bio); 90 } 91 92 /* 93 * We may have stale swap cache pages in memory: notice 94 * them here and get rid of the unnecessary final write. 95 */ 96 int swap_writepage(struct page *page, struct writeback_control *wbc) 97 { 98 struct bio *bio; 99 int ret = 0, rw = WRITE; 100 101 if (try_to_free_swap(page)) { 102 unlock_page(page); 103 goto out; 104 } 105 bio = get_swap_bio(GFP_NOIO, page_private(page), page, 106 end_swap_bio_write); 107 if (bio == NULL) { 108 set_page_dirty(page); 109 unlock_page(page); 110 ret = -ENOMEM; 111 goto out; 112 } 113 if (wbc->sync_mode == WB_SYNC_ALL) 114 rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG); 115 count_vm_event(PSWPOUT); 116 set_page_writeback(page); 117 unlock_page(page); 118 submit_bio(rw, bio); 119 out: 120 return ret; 121 } 122 123 int swap_readpage(struct page *page) 124 { 125 struct bio *bio; 126 int ret = 0; 127 128 VM_BUG_ON(!PageLocked(page)); 129 VM_BUG_ON(PageUptodate(page)); 130 bio = get_swap_bio(GFP_KERNEL, page_private(page), page, 131 end_swap_bio_read); 132 if (bio == NULL) { 133 unlock_page(page); 134 ret = -ENOMEM; 135 goto out; 136 } 137 count_vm_event(PSWPIN); 138 submit_bio(READ, bio); 139 out: 140 return ret; 141 } 142