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