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/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         count_vm_event(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         count_vm_event(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