root/mm/page_io.c

DEFINITIONS

1. get_swap_bio
2. end_swap_bio_write
3. end_swap_bio_read
4. swap_writepage
5. swap_readpage

/*
 *  linux/mm/page_io.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, 
 *  Asynchronous swapping added 30.12.95. Stephen Tweedie
 *  Removed race in async swapping. 14.4.1996. Bruno Haible
 *  Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
 *  Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
 */

#include <linux/mm.h>
#include <linux/kernel_stat.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/swapops.h>
#include <linux/writeback.h>
#include <asm/pgtable.h>

static struct bio *get_swap_bio(gfp_t gfp_flags, pgoff_t index,
                                struct page *page, bio_end_io_t end_io)
{
        struct bio *bio;

        bio = bio_alloc(gfp_flags, 1);
        if (bio) {
                struct swap_info_struct *sis;
                swp_entry_t entry = { .val = index, };

                sis = get_swap_info_struct(swp_type(entry));
                bio->bi_sector = map_swap_page(sis, swp_offset(entry)) *
                                        (PAGE_SIZE >> 9);
                bio->bi_bdev = sis->bdev;
                bio->bi_io_vec[0].bv_page = page;
                bio->bi_io_vec[0].bv_len = PAGE_SIZE;
                bio->bi_io_vec[0].bv_offset = 0;
                bio->bi_vcnt = 1;
                bio->bi_idx = 0;
                bio->bi_size = PAGE_SIZE;
                bio->bi_end_io = end_io;
        }
        return bio;
}

static void end_swap_bio_write(struct bio *bio, int err)
{
        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct page *page = bio->bi_io_vec[0].bv_page;

        if (!uptodate) {
                SetPageError(page);
                /*
                 * We failed to write the page out to swap-space.
                 * Re-dirty the page in order to avoid it being reclaimed.
                 * Also print a dire warning that things will go BAD (tm)
                 * very quickly.
                 *
                 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
                 */
                set_page_dirty(page);
                printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
                                imajor(bio->bi_bdev->bd_inode),
                                iminor(bio->bi_bdev->bd_inode),
                                (unsigned long long)bio->bi_sector);
                ClearPageReclaim(page);
        }
        end_page_writeback(page);
        bio_put(bio);
}

void end_swap_bio_read(struct bio *bio, int err)
{
        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
        struct page *page = bio->bi_io_vec[0].bv_page;

        if (!uptodate) {
                SetPageError(page);
                ClearPageUptodate(page);
                printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
                                imajor(bio->bi_bdev->bd_inode),
                                iminor(bio->bi_bdev->bd_inode),
                                (unsigned long long)bio->bi_sector);
        } else {
                SetPageUptodate(page);
        }
        unlock_page(page);
        bio_put(bio);
}

/*
 * We may have stale swap cache pages in memory: notice
 * them here and get rid of the unnecessary final write.
 */
int swap_writepage(struct page *page, struct writeback_control *wbc)
{
        struct bio *bio;
        int ret = 0, rw = WRITE;

        if (remove_exclusive_swap_page(page)) {
                unlock_page(page);
                goto out;
        }
        bio = get_swap_bio(GFP_NOIO, page_private(page), page,
                                end_swap_bio_write);
        if (bio == NULL) {
                set_page_dirty(page);
                unlock_page(page);
                ret = -ENOMEM;
                goto out;
        }
        if (wbc->sync_mode == WB_SYNC_ALL)
                rw |= (1 << BIO_RW_SYNC);
        count_vm_event(PSWPOUT);
        set_page_writeback(page);
        unlock_page(page);
        submit_bio(rw, bio);
out:
        return ret;
}

int swap_readpage(struct file *file, struct page *page)
{
        struct bio *bio;
        int ret = 0;

        BUG_ON(!PageLocked(page));
        BUG_ON(PageUptodate(page));
        bio = get_swap_bio(GFP_KERNEL, page_private(page), page,
                                end_swap_bio_read);
        if (bio == NULL) {
                unlock_page(page);
                ret = -ENOMEM;
                goto out;
        }
        count_vm_event(PSWPIN);
        submit_bio(READ, bio);
out:
        return ret;
}