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/writeback.h>
  21 #include <asm/pgtable.h>
  22
  23 static struct bio *get_swap_bio(gfp_t gfp_flags,
  24                                 struct page *page, bio_end_io_t end_io)
  25 {
  26         struct bio *bio;
  27
  28         bio = bio_alloc(gfp_flags, 1);
  29         if (bio) {
  30                 bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
  31                 bio->bi_sector <<= PAGE_SHIFT - 9;
  32                 bio->bi_io_vec[0].bv_page = page;
  33                 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
  34                 bio->bi_io_vec[0].bv_offset = 0;
  35                 bio->bi_vcnt = 1;
  36                 bio->bi_idx = 0;
  37                 bio->bi_size = PAGE_SIZE;
  38                 bio->bi_end_io = end_io;
  39         }
  40         return bio;
  41 }
  42
  43 static void end_swap_bio_write(struct bio *bio, int err)
  44 {
  45         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  46         struct page *page = bio->bi_io_vec[0].bv_page;
  47
  48         if (!uptodate) {
  49                 SetPageError(page);
  50                 /*
  51                  * We failed to write the page out to swap-space.
  52                  * Re-dirty the page in order to avoid it being reclaimed.
  53                  * Also print a dire warning that things will go BAD (tm)
  54                  * very quickly.
  55                  *
  56                  * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  57                  */
  58                 set_page_dirty(page);
  59                 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  60                                 imajor(bio->bi_bdev->bd_inode),
  61                                 iminor(bio->bi_bdev->bd_inode),
  62                                 (unsigned long long)bio->bi_sector);
  63                 ClearPageReclaim(page);
  64         }
  65         end_page_writeback(page);
  66         bio_put(bio);
  67 }
  68
  69 void end_swap_bio_read(struct bio *bio, int err)
  70 {
  71         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  72         struct page *page = bio->bi_io_vec[0].bv_page;
  73
  74         if (!uptodate) {
  75                 SetPageError(page);
  76                 ClearPageUptodate(page);
  77                 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  78                                 imajor(bio->bi_bdev->bd_inode),
  79                                 iminor(bio->bi_bdev->bd_inode),
  80                                 (unsigned long long)bio->bi_sector);
  81         } else {
  82                 SetPageUptodate(page);
  83         }
  84         unlock_page(page);
  85         bio_put(bio);
  86 }
  87
  88 /*
  89  * We may have stale swap cache pages in memory: notice
  90  * them here and get rid of the unnecessary final write.
  91  */
  92 int swap_writepage(struct page *page, struct writeback_control *wbc)
  93 {
  94         struct bio *bio;
  95         int ret = 0, rw = WRITE;
  96
  97         if (try_to_free_swap(page)) {
  98                 unlock_page(page);
  99                 goto out;
 100         }
 101         bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
 102         if (bio == NULL) {
 103                 set_page_dirty(page);
 104                 unlock_page(page);
 105                 ret = -ENOMEM;
 106                 goto out;
 107         }
 108         if (wbc->sync_mode == WB_SYNC_ALL)
 109                 rw |= REQ_SYNC | REQ_UNPLUG;
 110         count_vm_event(PSWPOUT);
 111         set_page_writeback(page);
 112         unlock_page(page);
 113         submit_bio(rw, bio);
 114 out:
 115         return ret;
 116 }
 117
 118 int swap_readpage(struct page *page)
 119 {
 120         struct bio *bio;
 121         int ret = 0;
 122
 123         VM_BUG_ON(!PageLocked(page));
 124         VM_BUG_ON(PageUptodate(page));
 125         bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
 126         if (bio == NULL) {
 127                 unlock_page(page);
 128                 ret = -ENOMEM;
 129                 goto out;
 130         }
 131         count_vm_event(PSWPIN);
 132         submit_bio(READ, bio);
 133 out:
 134         return ret;
 135 }