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,
  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                 swp_entry_t entry;
  30                 entry.val = page_private(page);
  31                 bio->bi_sector = map_swap_page(entry, &bio->bi_bdev);
  32                 bio->bi_sector <<= PAGE_SHIFT - 9;
  33                 bio->bi_io_vec[0].bv_page = page;
  34                 bio->bi_io_vec[0].bv_len = PAGE_SIZE;
  35                 bio->bi_io_vec[0].bv_offset = 0;
  36                 bio->bi_vcnt = 1;
  37                 bio->bi_idx = 0;
  38                 bio->bi_size = PAGE_SIZE;
  39                 bio->bi_end_io = end_io;
  40         }
  41         return bio;
  42 }
  43
  44 static void end_swap_bio_write(struct bio *bio, int err)
  45 {
  46         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  47         struct page *page = bio->bi_io_vec[0].bv_page;
  48
  49         if (!uptodate) {
  50                 SetPageError(page);
  51                 /*
  52                  * We failed to write the page out to swap-space.
  53                  * Re-dirty the page in order to avoid it being reclaimed.
  54                  * Also print a dire warning that things will go BAD (tm)
  55                  * very quickly.
  56                  *
  57                  * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  58                  */
  59                 set_page_dirty(page);
  60                 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  61                                 imajor(bio->bi_bdev->bd_inode),
  62                                 iminor(bio->bi_bdev->bd_inode),
  63                                 (unsigned long long)bio->bi_sector);
  64                 ClearPageReclaim(page);
  65         }
  66         end_page_writeback(page);
  67         bio_put(bio);
  68 }
  69
  70 void end_swap_bio_read(struct bio *bio, int err)
  71 {
  72         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  73         struct page *page = bio->bi_io_vec[0].bv_page;
  74
  75         if (!uptodate) {
  76                 SetPageError(page);
  77                 ClearPageUptodate(page);
  78                 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  79                                 imajor(bio->bi_bdev->bd_inode),
  80                                 iminor(bio->bi_bdev->bd_inode),
  81                                 (unsigned long long)bio->bi_sector);
  82         } else {
  83                 SetPageUptodate(page);
  84         }
  85         unlock_page(page);
  86         bio_put(bio);
  87 }
  88
  89 /*
  90  * We may have stale swap cache pages in memory: notice
  91  * them here and get rid of the unnecessary final write.
  92  */
  93 int swap_writepage(struct page *page, struct writeback_control *wbc)
  94 {
  95         struct bio *bio;
  96         int ret = 0, rw = WRITE;
  97
  98         if (try_to_free_swap(page)) {
  99                 unlock_page(page);
 100                 goto out;
 101         }
 102         bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
 103         if (bio == NULL) {
 104                 set_page_dirty(page);
 105                 unlock_page(page);
 106                 ret = -ENOMEM;
 107                 goto out;
 108         }
 109         if (wbc->sync_mode == WB_SYNC_ALL)
 110                 rw |= (1 << BIO_RW_SYNCIO) | (1 << BIO_RW_UNPLUG);
 111         count_vm_event(PSWPOUT);
 112         set_page_writeback(page);
 113         unlock_page(page);
 114         submit_bio(rw, bio);
 115 out:
 116         return ret;
 117 }
 118
 119 int swap_readpage(struct page *page)
 120 {
 121         struct bio *bio;
 122         int ret = 0;
 123
 124         VM_BUG_ON(!PageLocked(page));
 125         VM_BUG_ON(PageUptodate(page));
 126         bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
 127         if (bio == NULL) {
 128                 unlock_page(page);
 129                 ret = -ENOMEM;
 130                 goto out;
 131         }
 132         count_vm_event(PSWPIN);
 133         submit_bio(READ, bio);
 134 out:
 135         return ret;
 136 }