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/pagemap.h>
  16 #include <linux/swap.h>
  17 #include <linux/bio.h>
  18 #include <linux/swapops.h>
  19 #include <linux/buffer_head.h>  /* for block_sync_page() */
  20 #include <linux/mpage.h>
  21 #include <linux/writeback.h>
  22 #include <asm/pgtable.h>
  23
  24 static struct bio *
  25 get_swap_bio(int gfp_flags, struct page *page, bio_end_io_t end_io)
  26 {
  27         struct bio *bio;
  28
  29         bio = bio_alloc(gfp_flags, 1);
  30         if (bio) {
  31                 struct swap_info_struct *sis;
  32                 swp_entry_t entry;
  33
  34                 BUG_ON(!PageSwapCache(page));
  35                 entry.val = page->index;
  36                 sis = get_swap_info_struct(swp_type(entry));
  37
  38                 bio->bi_sector = map_swap_page(sis, swp_offset(entry)) *
  39                                         (PAGE_SIZE >> 9);
  40                 bio->bi_bdev = sis->bdev;
  41                 bio->bi_io_vec[0].bv_page = page;
  42                 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
  43                 bio->bi_io_vec[0].bv_offset = 0;
  44                 bio->bi_vcnt = 1;
  45                 bio->bi_idx = 0;
  46                 bio->bi_size = PAGE_SIZE;
  47                 bio->bi_end_io = end_io;
  48         }
  49         return bio;
  50 }
  51
  52 static int end_swap_bio_write(struct bio *bio, unsigned int bytes_done, int err)
  53 {
  54         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  55         struct page *page = bio->bi_io_vec[0].bv_page;
  56
  57         if (bio->bi_size)
  58                 return 1;
  59
  60         if (!uptodate)
  61                 SetPageError(page);
  62         end_page_writeback(page);
  63         bio_put(bio);
  64         return 0;
  65 }
  66
  67 static int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
  68 {
  69         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  70         struct page *page = bio->bi_io_vec[0].bv_page;
  71
  72         if (bio->bi_size)
  73                 return 1;
  74
  75         if (!uptodate) {
  76                 SetPageError(page);
  77                 ClearPageUptodate(page);
  78         } else {
  79                 SetPageUptodate(page);
  80         }
  81         unlock_page(page);
  82         bio_put(bio);
  83         return 0;
  84 }
  85
  86 /*
  87  * We may have stale swap cache pages in memory: notice
  88  * them here and get rid of the unnecessary final write.
  89  */
  90 int swap_writepage(struct page *page, struct writeback_control *wbc)
  91 {
  92         struct bio *bio;
  93         int ret = 0;
  94
  95         if (remove_exclusive_swap_page(page)) {
  96                 unlock_page(page);
  97                 goto out;
  98         }
  99         bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
 100         if (bio == NULL) {
 101                 set_page_dirty(page);
 102                 unlock_page(page);
 103                 ret = -ENOMEM;
 104                 goto out;
 105         }
 106         inc_page_state(pswpout);
 107         SetPageWriteback(page);
 108         unlock_page(page);
 109         submit_bio(WRITE, bio);
 110 out:
 111         return ret;
 112 }
 113
 114 int swap_readpage(struct file *file, struct page *page)
 115 {
 116         struct bio *bio;
 117         int ret = 0;
 118
 119         BUG_ON(!PageLocked(page));
 120         ClearPageUptodate(page);
 121         bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
 122         if (bio == NULL) {
 123                 unlock_page(page);
 124                 ret = -ENOMEM;
 125                 goto out;
 126         }
 127         inc_page_state(pswpin);
 128         submit_bio(READ, bio);
 129 out:
 130         return ret;
 131 }
 132
 133 struct address_space_operations swap_aops = {
 134         .writepage      = swap_writepage,
 135         .readpage       = swap_readpage,
 136         .sync_page      = block_sync_page,
 137         .set_page_dirty = __set_page_dirty_nobuffers,
 138 };
 139
 140 /*
 141  * A scruffy utility function to read or write an arbitrary swap page
 142  * and wait on the I/O.
 143  */
 144 int rw_swap_page_sync(int rw, swp_entry_t entry, struct page *page)
 145 {
 146         int ret;
 147         struct writeback_control swap_wbc = {
 148                 .sync_mode = WB_SYNC_ALL,
 149         };
 150
 151         lock_page(page);
 152
 153         BUG_ON(page->mapping);
 154         page->mapping = &swapper_space;
 155         page->index = entry.val;
 156
 157         if (rw == READ) {
 158                 ret = swap_readpage(NULL, page);
 159                 wait_on_page_locked(page);
 160         } else {
 161                 ret = swap_writepage(page, &swap_wbc);
 162                 wait_on_page_writeback(page);
 163         }
 164         page->mapping = NULL;
 165         if (ret == 0 && (!PageUptodate(page) || PageError(page)))
 166                 ret = -EIO;
 167         return ret;
 168 }