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   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 void end_swap_bio_write(struct bio *bio, 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 (!uptodate) {
  53                 SetPageError(page);
  54                 /*
  55                  * We failed to write the page out to swap-space.
  56                  * Re-dirty the page in order to avoid it being reclaimed.
  57                  * Also print a dire warning that things will go BAD (tm)
  58                  * very quickly.
  59                  *
  60                  * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  61                  */
  62                 set_page_dirty(page);
  63                 printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  64                                 imajor(bio->bi_bdev->bd_inode),
  65                                 iminor(bio->bi_bdev->bd_inode),
  66                                 (unsigned long long)bio->bi_sector);
  67                 ClearPageReclaim(page);
  68         }
  69         end_page_writeback(page);
  70         bio_put(bio);
  71 }
  72
  73 void end_swap_bio_read(struct bio *bio, int err)
  74 {
  75         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  76         struct page *page = bio->bi_io_vec[0].bv_page;
  77
  78         if (!uptodate) {
  79                 SetPageError(page);
  80                 ClearPageUptodate(page);
  81                 printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  82                                 imajor(bio->bi_bdev->bd_inode),
  83                                 iminor(bio->bi_bdev->bd_inode),
  84                                 (unsigned long long)bio->bi_sector);
  85         } else {
  86                 SetPageUptodate(page);
  87         }
  88         unlock_page(page);
  89         bio_put(bio);
  90 }
  91
  92 /*
  93  * We may have stale swap cache pages in memory: notice
  94  * them here and get rid of the unnecessary final write.
  95  */
  96 int swap_writepage(struct page *page, struct writeback_control *wbc)
  97 {
  98         struct bio *bio;
  99         int ret = 0, rw = WRITE;
 100
 101         if (try_to_free_swap(page)) {
 102                 unlock_page(page);
 103                 goto out;
 104         }
 105         bio = get_swap_bio(GFP_NOIO, page_private(page), page,
 106                                 end_swap_bio_write);
 107         if (bio == NULL) {
 108                 set_page_dirty(page);
 109                 unlock_page(page);
 110                 ret = -ENOMEM;
 111                 goto out;
 112         }
 113         if (wbc->sync_mode == WB_SYNC_ALL)
 114                 rw |= (1 << BIO_RW_SYNC);
 115         count_vm_event(PSWPOUT);
 116         set_page_writeback(page);
 117         unlock_page(page);
 118         submit_bio(rw, bio);
 119 out:
 120         return ret;
 121 }
 122
 123 int swap_readpage(struct file *file, struct page *page)
 124 {
 125         struct bio *bio;
 126         int ret = 0;
 127
 128         VM_BUG_ON(!PageLocked(page));
 129         VM_BUG_ON(PageUptodate(page));
 130         bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
 131                                 end_swap_bio_read);
 132         if (bio == NULL) {
 133                 unlock_page(page);
 134                 ret = -ENOMEM;
 135                 goto out;
 136         }
 137         count_vm_event(PSWPIN);
 138         submit_bio(READ, bio);
 139 out:
 140         return ret;
 141 }