LXR linux/mm/page

   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
  22static 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
  47static 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                /*
  58                 * We failed to write the page out to swap-space.
  59                 * Re-dirty the page in order to avoid it being reclaimed.
  60                 * Also print a dire warning that things will go BAD (tm)
  61                 * very quickly.
  62                 *
  63                 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  64                 */
  65                set_page_dirty(page);
  66                printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  67                                imajor(bio->bi_bdev->bd_inode),
  68                                iminor(bio->bi_bdev->bd_inode),
  69                                (unsigned long long)bio->bi_sector);
  70                ClearPageReclaim(page);
  71        }
  72        end_page_writeback(page);
  73        bio_put(bio);
  74        return 0;
  75}
  76
  77int end_swap_bio_read(struct bio *bio, unsigned int bytes_done, int err)
  78{
  79        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  80        struct page *page = bio->bi_io_vec[0].bv_page;
  81
  82        if (bio->bi_size)
  83                return 1;
  84
  85        if (!uptodate) {
  86                SetPageError(page);
  87                ClearPageUptodate(page);
  88                printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  89                                imajor(bio->bi_bdev->bd_inode),
  90                                iminor(bio->bi_bdev->bd_inode),
  91                                (unsigned long long)bio->bi_sector);
  92        } else {
  93                SetPageUptodate(page);
  94        }
  95        unlock_page(page);
  96        bio_put(bio);
  97        return 0;
  98}
  99
 100/*
 101 * We may have stale swap cache pages in memory: notice
 102 * them here and get rid of the unnecessary final write.
 103 */
 104int swap_writepage(struct page *page, struct writeback_control *wbc)
 105{
 106        struct bio *bio;
 107        int ret = 0, rw = WRITE;
 108
 109        if (remove_exclusive_swap_page(page)) {
 110                unlock_page(page);
 111                goto out;
 112        }
 113        bio = get_swap_bio(GFP_NOIO, page_private(page), page,
 114                                end_swap_bio_write);
 115        if (bio == NULL) {
 116                set_page_dirty(page);
 117                unlock_page(page);
 118                ret = -ENOMEM;
 119                goto out;
 120        }
 121        if (wbc->sync_mode == WB_SYNC_ALL)
 122                rw |= (1 << BIO_RW_SYNC);
 123        count_vm_event(PSWPOUT);
 124        set_page_writeback(page);
 125        unlock_page(page);
 126        submit_bio(rw, bio);
 127out:
 128        return ret;
 129}
 130
 131int swap_readpage(struct file *file, struct page *page)
 132{
 133        struct bio *bio;
 134        int ret = 0;
 135
 136        BUG_ON(!PageLocked(page));
 137        ClearPageUptodate(page);
 138        bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
 139                                end_swap_bio_read);
 140        if (bio == NULL) {
 141                unlock_page(page);
 142                ret = -ENOMEM;
 143                goto out;
 144        }
 145        count_vm_event(PSWPIN);
 146        submit_bio(READ, bio);
 147out:
 148        return ret;
 149}
 150