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 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
  73void 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 */
  96int 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_SYNCIO) | (1 << BIO_RW_UNPLUG);
 115        count_vm_event(PSWPOUT);
 116        set_page_writeback(page);
 117        unlock_page(page);
 118        submit_bio(rw, bio);
 119out:
 120        return ret;
 121}
 122
 123int swap_readpage(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);
 139out:
 140        return ret;
 141}
 142