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![Minchan Kim](/assets/img/avatar_default.png)
If a block device supports rw_page operation, it doesn't submit bios so the annotation in submit_bio() for refault stall doesn't work. It happens with zram in android, especially swap read path which could consume CPU cycle for decompress. It is also a problem for zswap which uses frontswap. Annotate swap_readpage() to account the synchronous IO overhead to prevent underreport memory pressure. [akpm@linux-foundation.org: add comment, per Johannes] Link: http://lkml.kernel.org/r/20191010152134.38545-1-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@google.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Reviewed-by: Shakeel Butt <shakeelb@google.com> Cc: Seth Jennings <sjenning@redhat.com> Cc: Dan Streetman <ddstreet@ieee.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
447 lines
11 KiB
C
447 lines
11 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/page_io.c
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*
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Swap reorganised 29.12.95,
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* Asynchronous swapping added 30.12.95. Stephen Tweedie
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* Removed race in async swapping. 14.4.1996. Bruno Haible
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* Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
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* Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
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*/
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#include <linux/mm.h>
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#include <linux/kernel_stat.h>
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#include <linux/gfp.h>
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#include <linux/pagemap.h>
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#include <linux/swap.h>
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#include <linux/bio.h>
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#include <linux/swapops.h>
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#include <linux/buffer_head.h>
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#include <linux/writeback.h>
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#include <linux/frontswap.h>
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#include <linux/blkdev.h>
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#include <linux/psi.h>
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#include <linux/uio.h>
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#include <linux/sched/task.h>
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#include <asm/pgtable.h>
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static struct bio *get_swap_bio(gfp_t gfp_flags,
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struct page *page, bio_end_io_t end_io)
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{
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struct bio *bio;
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bio = bio_alloc(gfp_flags, 1);
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if (bio) {
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struct block_device *bdev;
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bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
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bio_set_dev(bio, bdev);
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bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
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bio->bi_end_io = end_io;
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bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
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}
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return bio;
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}
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void end_swap_bio_write(struct bio *bio)
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{
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struct page *page = bio_first_page_all(bio);
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if (bio->bi_status) {
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SetPageError(page);
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/*
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* We failed to write the page out to swap-space.
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* Re-dirty the page in order to avoid it being reclaimed.
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* Also print a dire warning that things will go BAD (tm)
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* very quickly.
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*
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* Also clear PG_reclaim to avoid rotate_reclaimable_page()
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*/
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set_page_dirty(page);
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pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
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MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
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(unsigned long long)bio->bi_iter.bi_sector);
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ClearPageReclaim(page);
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}
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end_page_writeback(page);
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bio_put(bio);
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}
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static void swap_slot_free_notify(struct page *page)
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{
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struct swap_info_struct *sis;
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struct gendisk *disk;
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swp_entry_t entry;
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/*
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* There is no guarantee that the page is in swap cache - the software
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* suspend code (at least) uses end_swap_bio_read() against a non-
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* swapcache page. So we must check PG_swapcache before proceeding with
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* this optimization.
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*/
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if (unlikely(!PageSwapCache(page)))
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return;
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sis = page_swap_info(page);
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if (!(sis->flags & SWP_BLKDEV))
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return;
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/*
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* The swap subsystem performs lazy swap slot freeing,
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* expecting that the page will be swapped out again.
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* So we can avoid an unnecessary write if the page
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* isn't redirtied.
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* This is good for real swap storage because we can
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* reduce unnecessary I/O and enhance wear-leveling
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* if an SSD is used as the as swap device.
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* But if in-memory swap device (eg zram) is used,
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* this causes a duplicated copy between uncompressed
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* data in VM-owned memory and compressed data in
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* zram-owned memory. So let's free zram-owned memory
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* and make the VM-owned decompressed page *dirty*,
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* so the page should be swapped out somewhere again if
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* we again wish to reclaim it.
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*/
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disk = sis->bdev->bd_disk;
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entry.val = page_private(page);
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if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
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unsigned long offset;
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offset = swp_offset(entry);
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SetPageDirty(page);
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disk->fops->swap_slot_free_notify(sis->bdev,
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offset);
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}
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}
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static void end_swap_bio_read(struct bio *bio)
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{
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struct page *page = bio_first_page_all(bio);
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struct task_struct *waiter = bio->bi_private;
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if (bio->bi_status) {
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SetPageError(page);
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ClearPageUptodate(page);
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pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
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MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
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(unsigned long long)bio->bi_iter.bi_sector);
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goto out;
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}
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SetPageUptodate(page);
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swap_slot_free_notify(page);
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out:
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unlock_page(page);
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WRITE_ONCE(bio->bi_private, NULL);
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bio_put(bio);
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if (waiter) {
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blk_wake_io_task(waiter);
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put_task_struct(waiter);
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}
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}
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int generic_swapfile_activate(struct swap_info_struct *sis,
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struct file *swap_file,
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sector_t *span)
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{
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struct address_space *mapping = swap_file->f_mapping;
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struct inode *inode = mapping->host;
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unsigned blocks_per_page;
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unsigned long page_no;
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unsigned blkbits;
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sector_t probe_block;
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sector_t last_block;
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sector_t lowest_block = -1;
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sector_t highest_block = 0;
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int nr_extents = 0;
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int ret;
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blkbits = inode->i_blkbits;
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blocks_per_page = PAGE_SIZE >> blkbits;
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/*
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* Map all the blocks into the extent tree. This code doesn't try
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* to be very smart.
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*/
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probe_block = 0;
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page_no = 0;
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last_block = i_size_read(inode) >> blkbits;
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while ((probe_block + blocks_per_page) <= last_block &&
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page_no < sis->max) {
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unsigned block_in_page;
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sector_t first_block;
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cond_resched();
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first_block = bmap(inode, probe_block);
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if (first_block == 0)
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goto bad_bmap;
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/*
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* It must be PAGE_SIZE aligned on-disk
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*/
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if (first_block & (blocks_per_page - 1)) {
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probe_block++;
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goto reprobe;
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}
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for (block_in_page = 1; block_in_page < blocks_per_page;
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block_in_page++) {
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sector_t block;
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block = bmap(inode, probe_block + block_in_page);
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if (block == 0)
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goto bad_bmap;
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if (block != first_block + block_in_page) {
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/* Discontiguity */
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probe_block++;
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goto reprobe;
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}
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}
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first_block >>= (PAGE_SHIFT - blkbits);
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if (page_no) { /* exclude the header page */
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if (first_block < lowest_block)
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lowest_block = first_block;
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if (first_block > highest_block)
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highest_block = first_block;
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}
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/*
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* We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
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*/
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ret = add_swap_extent(sis, page_no, 1, first_block);
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if (ret < 0)
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goto out;
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nr_extents += ret;
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page_no++;
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probe_block += blocks_per_page;
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reprobe:
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continue;
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}
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ret = nr_extents;
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*span = 1 + highest_block - lowest_block;
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if (page_no == 0)
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page_no = 1; /* force Empty message */
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sis->max = page_no;
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sis->pages = page_no - 1;
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sis->highest_bit = page_no - 1;
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out:
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return ret;
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bad_bmap:
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pr_err("swapon: swapfile has holes\n");
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ret = -EINVAL;
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goto out;
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}
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/*
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* We may have stale swap cache pages in memory: notice
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* them here and get rid of the unnecessary final write.
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*/
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int swap_writepage(struct page *page, struct writeback_control *wbc)
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{
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int ret = 0;
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if (try_to_free_swap(page)) {
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unlock_page(page);
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goto out;
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}
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if (frontswap_store(page) == 0) {
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set_page_writeback(page);
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unlock_page(page);
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end_page_writeback(page);
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goto out;
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}
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ret = __swap_writepage(page, wbc, end_swap_bio_write);
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out:
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return ret;
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}
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static sector_t swap_page_sector(struct page *page)
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{
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return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
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}
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static inline void count_swpout_vm_event(struct page *page)
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{
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#ifdef CONFIG_TRANSPARENT_HUGEPAGE
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if (unlikely(PageTransHuge(page)))
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count_vm_event(THP_SWPOUT);
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#endif
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count_vm_events(PSWPOUT, hpage_nr_pages(page));
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}
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int __swap_writepage(struct page *page, struct writeback_control *wbc,
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bio_end_io_t end_write_func)
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{
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struct bio *bio;
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int ret;
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struct swap_info_struct *sis = page_swap_info(page);
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VM_BUG_ON_PAGE(!PageSwapCache(page), page);
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if (sis->flags & SWP_FS) {
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struct kiocb kiocb;
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struct file *swap_file = sis->swap_file;
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struct address_space *mapping = swap_file->f_mapping;
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struct bio_vec bv = {
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.bv_page = page,
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.bv_len = PAGE_SIZE,
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.bv_offset = 0
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};
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struct iov_iter from;
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iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
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init_sync_kiocb(&kiocb, swap_file);
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kiocb.ki_pos = page_file_offset(page);
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set_page_writeback(page);
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unlock_page(page);
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ret = mapping->a_ops->direct_IO(&kiocb, &from);
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if (ret == PAGE_SIZE) {
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count_vm_event(PSWPOUT);
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ret = 0;
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} else {
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/*
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* In the case of swap-over-nfs, this can be a
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* temporary failure if the system has limited
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* memory for allocating transmit buffers.
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* Mark the page dirty and avoid
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* rotate_reclaimable_page but rate-limit the
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* messages but do not flag PageError like
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* the normal direct-to-bio case as it could
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* be temporary.
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*/
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set_page_dirty(page);
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ClearPageReclaim(page);
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pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
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page_file_offset(page));
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}
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end_page_writeback(page);
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return ret;
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}
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ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
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if (!ret) {
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count_swpout_vm_event(page);
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return 0;
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}
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ret = 0;
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bio = get_swap_bio(GFP_NOIO, page, end_write_func);
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if (bio == NULL) {
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set_page_dirty(page);
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unlock_page(page);
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ret = -ENOMEM;
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goto out;
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}
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bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
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bio_associate_blkg_from_page(bio, page);
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count_swpout_vm_event(page);
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set_page_writeback(page);
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unlock_page(page);
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submit_bio(bio);
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out:
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return ret;
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}
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int swap_readpage(struct page *page, bool synchronous)
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{
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struct bio *bio;
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int ret = 0;
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struct swap_info_struct *sis = page_swap_info(page);
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blk_qc_t qc;
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struct gendisk *disk;
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unsigned long pflags;
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VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
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VM_BUG_ON_PAGE(!PageLocked(page), page);
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VM_BUG_ON_PAGE(PageUptodate(page), page);
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/*
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* Count submission time as memory stall. When the device is congested,
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* or the submitting cgroup IO-throttled, submission can be a
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* significant part of overall IO time.
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*/
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psi_memstall_enter(&pflags);
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if (frontswap_load(page) == 0) {
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SetPageUptodate(page);
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unlock_page(page);
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goto out;
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}
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if (sis->flags & SWP_FS) {
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struct file *swap_file = sis->swap_file;
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struct address_space *mapping = swap_file->f_mapping;
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ret = mapping->a_ops->readpage(swap_file, page);
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if (!ret)
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count_vm_event(PSWPIN);
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goto out;
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}
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ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
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if (!ret) {
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if (trylock_page(page)) {
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swap_slot_free_notify(page);
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unlock_page(page);
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}
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count_vm_event(PSWPIN);
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goto out;
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}
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ret = 0;
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bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
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if (bio == NULL) {
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unlock_page(page);
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ret = -ENOMEM;
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goto out;
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}
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disk = bio->bi_disk;
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/*
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* Keep this task valid during swap readpage because the oom killer may
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* attempt to access it in the page fault retry time check.
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*/
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bio_set_op_attrs(bio, REQ_OP_READ, 0);
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if (synchronous) {
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bio->bi_opf |= REQ_HIPRI;
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get_task_struct(current);
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bio->bi_private = current;
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}
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count_vm_event(PSWPIN);
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bio_get(bio);
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qc = submit_bio(bio);
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while (synchronous) {
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set_current_state(TASK_UNINTERRUPTIBLE);
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if (!READ_ONCE(bio->bi_private))
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break;
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if (!blk_poll(disk->queue, qc, true))
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io_schedule();
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}
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__set_current_state(TASK_RUNNING);
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bio_put(bio);
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out:
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psi_memstall_leave(&pflags);
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return ret;
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}
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int swap_set_page_dirty(struct page *page)
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{
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struct swap_info_struct *sis = page_swap_info(page);
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if (sis->flags & SWP_FS) {
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struct address_space *mapping = sis->swap_file->f_mapping;
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VM_BUG_ON_PAGE(!PageSwapCache(page), page);
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return mapping->a_ops->set_page_dirty(page);
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} else {
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return __set_page_dirty_no_writeback(page);
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}
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}
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