linux/mm/page_io.c
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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/gfp.h>
  16#include <linux/pagemap.h>
  17#include <linux/swap.h>
  18#include <linux/bio.h>
  19#include <linux/swapops.h>
  20#include <linux/writeback.h>
  21#include <asm/pgtable.h>
  22
  23static struct bio *get_swap_bio(gfp_t gfp_flags,
  24                                struct page *page, bio_end_io_t end_io)
  25{
  26        struct bio *bio;
  27
  28        bio = bio_alloc(gfp_flags, 1);
  29        if (bio) {
  30                bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
  31                bio->bi_sector <<= PAGE_SHIFT - 9;
  32                bio->bi_io_vec[0].bv_page = page;
  33                bio->bi_io_vec[0].bv_len = PAGE_SIZE;
  34                bio->bi_io_vec[0].bv_offset = 0;
  35                bio->bi_vcnt = 1;
  36                bio->bi_idx = 0;
  37                bio->bi_size = PAGE_SIZE;
  38                bio->bi_end_io = end_io;
  39        }
  40        return bio;
  41}
  42
  43static void end_swap_bio_write(struct bio *bio, int err)
  44{
  45        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  46        struct page *page = bio->bi_io_vec[0].bv_page;
  47
  48        if (!uptodate) {
  49                SetPageError(page);
  50                /*
  51                 * We failed to write the page out to swap-space.
  52                 * Re-dirty the page in order to avoid it being reclaimed.
  53                 * Also print a dire warning that things will go BAD (tm)
  54                 * very quickly.
  55                 *
  56                 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  57                 */
  58                set_page_dirty(page);
  59                printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  60                                imajor(bio->bi_bdev->bd_inode),
  61                                iminor(bio->bi_bdev->bd_inode),
  62                                (unsigned long long)bio->bi_sector);
  63                ClearPageReclaim(page);
  64        }
  65        end_page_writeback(page);
  66        bio_put(bio);
  67}
  68
  69void end_swap_bio_read(struct bio *bio, int err)
  70{
  71        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  72        struct page *page = bio->bi_io_vec[0].bv_page;
  73
  74        if (!uptodate) {
  75                SetPageError(page);
  76                ClearPageUptodate(page);
  77                printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  78                                imajor(bio->bi_bdev->bd_inode),
  79                                iminor(bio->bi_bdev->bd_inode),
  80                                (unsigned long long)bio->bi_sector);
  81        } else {
  82                SetPageUptodate(page);
  83        }
  84        unlock_page(page);
  85        bio_put(bio);
  86}
  87
  88/*
  89 * We may have stale swap cache pages in memory: notice
  90 * them here and get rid of the unnecessary final write.
  91 */
  92int swap_writepage(struct page *page, struct writeback_control *wbc)
  93{
  94        struct bio *bio;
  95        int ret = 0, rw = WRITE;
  96
  97        if (try_to_free_swap(page)) {
  98                unlock_page(page);
  99                goto out;
 100        }
 101        bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
 102        if (bio == NULL) {
 103                set_page_dirty(page);
 104                unlock_page(page);
 105                ret = -ENOMEM;
 106                goto out;
 107        }
 108        if (wbc->sync_mode == WB_SYNC_ALL)
 109                rw |= REQ_SYNC;
 110        count_vm_event(PSWPOUT);
 111        set_page_writeback(page);
 112        unlock_page(page);
 113        submit_bio(rw, bio);
 114out:
 115        return ret;
 116}
 117
 118int swap_readpage(struct page *page)
 119{
 120        struct bio *bio;
 121        int ret = 0;
 122
 123        VM_BUG_ON(!PageLocked(page));
 124        VM_BUG_ON(PageUptodate(page));
 125        bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
 126        if (bio == NULL) {
 127                unlock_page(page);
 128                ret = -ENOMEM;
 129                goto out;
 130        }
 131        count_vm_event(PSWPIN);
 132        submit_bio(READ, bio);
 133out:
 134        return ret;
 135}
 136
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