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/*

 *  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));

        ClearPageUptodate(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;

}