mm/page_io.c

   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/gfp.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/swap.h>
  18 #include <linux/bio.h>
  19 #include <linux/swapops.h>
  20 #include <linux/buffer_head.h>
  21 #include <linux/writeback.h>
  22 #include <linux/frontswap.h>
  23 #include <asm/pgtable.h>
  24
  25 static struct bio *get_swap_bio(gfp_t gfp_flags,
  26                                 struct page *page, bio_end_io_t end_io)
  27 {
  28         struct bio *bio;
  29
  30         bio = bio_alloc(gfp_flags, 1);
  31         if (bio) {
  32                 bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
  33                 bio->bi_sector <<= PAGE_SHIFT - 9;
  34                 bio->bi_io_vec[0].bv_page = page;
  35                 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
  36                 bio->bi_io_vec[0].bv_offset = 0;
  37                 bio->bi_vcnt = 1;
  38                 bio->bi_idx = 0;
  39                 bio->bi_size = PAGE_SIZE;
  40                 bio->bi_end_io = end_io;
  41         }
  42         return bio;
  43 }
  44
  45 static void end_swap_bio_write(struct bio *bio, int err)
  46 {
  47         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  48         struct page *page = bio->bi_io_vec[0].bv_page;
  49
  50         if (!uptodate) {
  51                 SetPageError(page);
  52                 /*
  53                  * We failed to write the page out to swap-space.
  54                  * Re-dirty the page in order to avoid it being reclaimed.
  55                  * Also print a dire warning that things will go BAD (tm)
  56                  * very quickly.
  57                  *
  58                  * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  59                  */
  60                 set_page_dirty(page);
  61                 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  62                                 imajor(bio->bi_bdev->bd_inode),
  63                                 iminor(bio->bi_bdev->bd_inode),
  64                                 (unsigned long long)bio->bi_sector);
  65                 ClearPageReclaim(page);
  66         }
  67         end_page_writeback(page);
  68         bio_put(bio);
  69 }
  70
  71 void end_swap_bio_read(struct bio *bio, int err)
  72 {
  73         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  74         struct page *page = bio->bi_io_vec[0].bv_page;
  75
  76         if (!uptodate) {
  77                 SetPageError(page);
  78                 ClearPageUptodate(page);
  79                 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  80                                 imajor(bio->bi_bdev->bd_inode),
  81                                 iminor(bio->bi_bdev->bd_inode),
  82                                 (unsigned long long)bio->bi_sector);
  83         } else {
  84                 SetPageUptodate(page);
  85         }
  86         unlock_page(page);
  87         bio_put(bio);
  88 }
  89
  90 /*
  91  * We may have stale swap cache pages in memory: notice
  92  * them here and get rid of the unnecessary final write.
  93  */
  94 int swap_writepage(struct page *page, struct writeback_control *wbc)
  95 {
  96         struct bio *bio;
  97         int ret = 0, rw = WRITE;
  98         struct swap_info_struct *sis = page_swap_info(page);
  99
 100         if (try_to_free_swap(page)) {
 101                 unlock_page(page);
 102                 goto out;
 103         }
 104         if (frontswap_store(page) == 0) {
 105                 set_page_writeback(page);
 106                 unlock_page(page);
 107                 end_page_writeback(page);
 108                 goto out;
 109         }
 110
 111         if (sis->flags & SWP_FILE) {
 112                 struct kiocb kiocb;
 113                 struct file *swap_file = sis->swap_file;
 114                 struct address_space *mapping = swap_file->f_mapping;
 115                 struct iovec iov = {
 116                         .iov_base = page_address(page),
 117                         .iov_len  = PAGE_SIZE,
 118                 };
 119
 120                 init_sync_kiocb(&kiocb, swap_file);
 121                 kiocb.ki_pos = page_file_offset(page);
 122                 kiocb.ki_left = PAGE_SIZE;
 123                 kiocb.ki_nbytes = PAGE_SIZE;
 124
 125                 unlock_page(page);
 126                 ret = mapping->a_ops->direct_IO(KERNEL_WRITE,
 127                                                 &kiocb, &iov,
 128                                                 kiocb.ki_pos, 1);
 129                 if (ret == PAGE_SIZE) {
 130                         count_vm_event(PSWPOUT);
 131                         ret = 0;
 132                 }
 133                 return ret;
 134         }
 135
 136         bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
 137         if (bio == NULL) {
 138                 set_page_dirty(page);
 139                 unlock_page(page);
 140                 ret = -ENOMEM;
 141                 goto out;
 142         }
 143         if (wbc->sync_mode == WB_SYNC_ALL)
 144                 rw |= REQ_SYNC;
 145         count_vm_event(PSWPOUT);
 146         set_page_writeback(page);
 147         unlock_page(page);
 148         submit_bio(rw, bio);
 149 out:
 150         return ret;
 151 }
 152
 153 int swap_readpage(struct page *page)
 154 {
 155         struct bio *bio;
 156         int ret = 0;
 157         struct swap_info_struct *sis = page_swap_info(page);
 158
 159         VM_BUG_ON(!PageLocked(page));
 160         VM_BUG_ON(PageUptodate(page));
 161         if (frontswap_load(page) == 0) {
 162                 SetPageUptodate(page);
 163                 unlock_page(page);
 164                 goto out;
 165         }
 166
 167         if (sis->flags & SWP_FILE) {
 168                 struct file *swap_file = sis->swap_file;
 169                 struct address_space *mapping = swap_file->f_mapping;
 170
 171                 ret = mapping->a_ops->readpage(swap_file, page);
 172                 if (!ret)
 173                         count_vm_event(PSWPIN);
 174                 return ret;
 175         }
 176
 177         bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
 178         if (bio == NULL) {
 179                 unlock_page(page);
 180                 ret = -ENOMEM;
 181                 goto out;
 182         }
 183         count_vm_event(PSWPIN);
 184         submit_bio(READ, bio);
 185 out:
 186         return ret;
 187 }
 188
 189 int swap_set_page_dirty(struct page *page)
 190 {
 191         struct swap_info_struct *sis = page_swap_info(page);
 192
 193         if (sis->flags & SWP_FILE) {
 194                 struct address_space *mapping = sis->swap_file->f_mapping;
 195                 return mapping->a_ops->set_page_dirty(page);
 196         } else {
 197                 return __set_page_dirty_no_writeback(page);
 198         }
 199 }