[mirror_ubuntu-focal-kernel.git] / mm / page_io.c

// SPDX-License-Identifier: GPL-2.0
/*
 *  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/gfp.h>
#include <linux/pagemap.h>
#include <linux/swap.h>
#include <linux/bio.h>
#include <linux/swapops.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/frontswap.h>
#include <linux/blkdev.h>
#include <linux/uio.h>
#include <linux/sched/task.h>
#include <asm/pgtable.h>

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

	bio = bio_alloc(gfp_flags, 1);
	if (bio) {
		struct block_device *bdev;

		bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
		bio_set_dev(bio, bdev);
		bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
		bio->bi_end_io = end_io;

		bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
	}
	return bio;
}

void end_swap_bio_write(struct bio *bio)
{
	struct page *page = bio_first_page_all(bio);

	if (bio->bi_status) {
		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);
		pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
			 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
			 (unsigned long long)bio->bi_iter.bi_sector);
		ClearPageReclaim(page);
	}
	end_page_writeback(page);
	bio_put(bio);
}

static void swap_slot_free_notify(struct page *page)
{
	struct swap_info_struct *sis;
	struct gendisk *disk;
	swp_entry_t entry;

	/*
	 * There is no guarantee that the page is in swap cache - the software
	 * suspend code (at least) uses end_swap_bio_read() against a non-
	 * swapcache page.  So we must check PG_swapcache before proceeding with
	 * this optimization.
	 */
	if (unlikely(!PageSwapCache(page)))
		return;

	sis = page_swap_info(page);
	if (!(sis->flags & SWP_BLKDEV))
		return;

	/*
	 * The swap subsystem performs lazy swap slot freeing,
	 * expecting that the page will be swapped out again.
	 * So we can avoid an unnecessary write if the page
	 * isn't redirtied.
	 * This is good for real swap storage because we can
	 * reduce unnecessary I/O and enhance wear-leveling
	 * if an SSD is used as the as swap device.
	 * But if in-memory swap device (eg zram) is used,
	 * this causes a duplicated copy between uncompressed
	 * data in VM-owned memory and compressed data in
	 * zram-owned memory.  So let's free zram-owned memory
	 * and make the VM-owned decompressed page *dirty*,
	 * so the page should be swapped out somewhere again if
	 * we again wish to reclaim it.
	 */
	disk = sis->bdev->bd_disk;
	entry.val = page_private(page);
	if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
		unsigned long offset;

		offset = swp_offset(entry);

		SetPageDirty(page);
		disk->fops->swap_slot_free_notify(sis->bdev,
				offset);
	}
}

static void end_swap_bio_read(struct bio *bio)
{
	struct page *page = bio_first_page_all(bio);
	struct task_struct *waiter = bio->bi_private;

	if (bio->bi_status) {
		SetPageError(page);
		ClearPageUptodate(page);
		pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
			 MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
			 (unsigned long long)bio->bi_iter.bi_sector);
		goto out;
	}

	SetPageUptodate(page);
	swap_slot_free_notify(page);
out:
	unlock_page(page);
	WRITE_ONCE(bio->bi_private, NULL);
	bio_put(bio);
	if (waiter) {
		blk_wake_io_task(waiter);
		put_task_struct(waiter);
	}
}

int generic_swapfile_activate(struct swap_info_struct *sis,
				struct file *swap_file,
				sector_t *span)
{
	struct address_space *mapping = swap_file->f_mapping;
	struct inode *inode = mapping->host;
	unsigned blocks_per_page;
	unsigned long page_no;
	unsigned blkbits;
	sector_t probe_block;
	sector_t last_block;
	sector_t lowest_block = -1;
	sector_t highest_block = 0;
	int nr_extents = 0;
	int ret;

	blkbits = inode->i_blkbits;
	blocks_per_page = PAGE_SIZE >> blkbits;

	/*
	 * Map all the blocks into the extent tree.  This code doesn't try
	 * to be very smart.
	 */
	probe_block = 0;
	page_no = 0;
	last_block = i_size_read(inode) >> blkbits;
	while ((probe_block + blocks_per_page) <= last_block &&
			page_no < sis->max) {
		unsigned block_in_page;
		sector_t first_block;

		cond_resched();

		first_block = bmap(inode, probe_block);
		if (first_block == 0)
			goto bad_bmap;

		/*
		 * It must be PAGE_SIZE aligned on-disk
		 */
		if (first_block & (blocks_per_page - 1)) {
			probe_block++;
			goto reprobe;
		}

		for (block_in_page = 1; block_in_page < blocks_per_page;
					block_in_page++) {
			sector_t block;

			block = bmap(inode, probe_block + block_in_page);
			if (block == 0)
				goto bad_bmap;
			if (block != first_block + block_in_page) {
				/* Discontiguity */
				probe_block++;
				goto reprobe;
			}
		}

		first_block >>= (PAGE_SHIFT - blkbits);
		if (page_no) {	/* exclude the header page */
			if (first_block < lowest_block)
				lowest_block = first_block;
			if (first_block > highest_block)
				highest_block = first_block;
		}

		/*
		 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
		 */
		ret = add_swap_extent(sis, page_no, 1, first_block);
		if (ret < 0)
			goto out;
		nr_extents += ret;
		page_no++;
		probe_block += blocks_per_page;
reprobe:
		continue;
	}
	ret = nr_extents;
	*span = 1 + highest_block - lowest_block;
	if (page_no == 0)
		page_no = 1;	/* force Empty message */
	sis->max = page_no;
	sis->pages = page_no - 1;
	sis->highest_bit = page_no - 1;
out:
	return ret;
bad_bmap:
	pr_err("swapon: swapfile has holes\n");
	ret = -EINVAL;
	goto out;
}

/*
 * 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)
{
	int ret = 0;

	if (try_to_free_swap(page)) {
		unlock_page(page);
		goto out;
	}
	if (frontswap_store(page) == 0) {
		set_page_writeback(page);
		unlock_page(page);
		end_page_writeback(page);
		goto out;
	}
	ret = __swap_writepage(page, wbc, end_swap_bio_write);
out:
	return ret;
}

static inline void count_swpout_vm_event(struct page *page)
{
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	if (unlikely(PageTransHuge(page)))
		count_vm_event(THP_SWPOUT);
#endif
	count_vm_events(PSWPOUT, hpage_nr_pages(page));
}

int __swap_writepage(struct page *page, struct writeback_control *wbc,
		bio_end_io_t end_write_func)
{
	struct bio *bio;
	int ret;
	struct swap_info_struct *sis = page_swap_info(page);

	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
	if (sis->flags & SWP_FS) {
		struct kiocb kiocb;
		struct file *swap_file = sis->swap_file;
		struct address_space *mapping = swap_file->f_mapping;
		struct bio_vec bv = {
			.bv_page = page,
			.bv_len  = PAGE_SIZE,
			.bv_offset = 0
		};
		struct iov_iter from;

		iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
		init_sync_kiocb(&kiocb, swap_file);
		kiocb.ki_pos = page_file_offset(page);

		set_page_writeback(page);
		unlock_page(page);
		ret = mapping->a_ops->direct_IO(&kiocb, &from);
		if (ret == PAGE_SIZE) {
			count_vm_event(PSWPOUT);
			ret = 0;
		} else {
			/*
			 * In the case of swap-over-nfs, this can be a
			 * temporary failure if the system has limited
			 * memory for allocating transmit buffers.
			 * Mark the page dirty and avoid
			 * rotate_reclaimable_page but rate-limit the
			 * messages but do not flag PageError like
			 * the normal direct-to-bio case as it could
			 * be temporary.
			 */
			set_page_dirty(page);
			ClearPageReclaim(page);
			pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
					   page_file_offset(page));
		}
		end_page_writeback(page);
		return ret;
	}

	ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
	if (!ret) {
		count_swpout_vm_event(page);
		return 0;
	}

	ret = 0;
	bio = get_swap_bio(GFP_NOIO, page, end_write_func);
	if (bio == NULL) {
		set_page_dirty(page);
		unlock_page(page);
		ret = -ENOMEM;
		goto out;
	}
	bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
	bio_associate_blkg_from_page(bio, page);
	count_swpout_vm_event(page);
	set_page_writeback(page);
	unlock_page(page);
	submit_bio(bio);
out:
	return ret;
}

int swap_readpage(struct page *page, bool synchronous)
{
	struct bio *bio;
	int ret = 0;
	struct swap_info_struct *sis = page_swap_info(page);
	blk_qc_t qc;
	struct gendisk *disk;

	VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
	VM_BUG_ON_PAGE(!PageLocked(page), page);
	VM_BUG_ON_PAGE(PageUptodate(page), page);
	if (frontswap_load(page) == 0) {
		SetPageUptodate(page);
		unlock_page(page);
		goto out;
	}

	if (sis->flags & SWP_FS) {
		struct file *swap_file = sis->swap_file;
		struct address_space *mapping = swap_file->f_mapping;

		ret = mapping->a_ops->readpage(swap_file, page);
		if (!ret)
			count_vm_event(PSWPIN);
		return ret;
	}

	ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
	if (!ret) {
		if (trylock_page(page)) {
			swap_slot_free_notify(page);
			unlock_page(page);
		}

		count_vm_event(PSWPIN);
		return 0;
	}

	ret = 0;
	bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
	if (bio == NULL) {
		unlock_page(page);
		ret = -ENOMEM;
		goto out;
	}
	disk = bio->bi_disk;
	/*
	 * Keep this task valid during swap readpage because the oom killer may
	 * attempt to access it in the page fault retry time check.
	 */
	bio_set_op_attrs(bio, REQ_OP_READ, 0);
	if (synchronous) {
		bio->bi_opf |= REQ_HIPRI;
		get_task_struct(current);
		bio->bi_private = current;
	}
	count_vm_event(PSWPIN);
	bio_get(bio);
	qc = submit_bio(bio);
	while (synchronous) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (!READ_ONCE(bio->bi_private))
			break;

		if (!blk_poll(disk->queue, qc, true))
			io_schedule();
	}
	__set_current_state(TASK_RUNNING);
	bio_put(bio);

out:
	return ret;
}

int swap_set_page_dirty(struct page *page)
{
	struct swap_info_struct *sis = page_swap_info(page);

	if (sis->flags & SWP_FS) {
		struct address_space *mapping = sis->swap_file->f_mapping;

		VM_BUG_ON_PAGE(!PageSwapCache(page), page);
		return mapping->a_ops->set_page_dirty(page);
	} else {
		return __set_page_dirty_no_writeback(page);
	}
}
Commit	Line	Data
b2441318	1	// SPDX-License-Identifier: GPL-2.0
1da177e4 LT	2	/*
	3	* linux/mm/page_io.c
	4	*
	5	* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
	6	*
	7	* Swap reorganised 29.12.95,
	8	* Asynchronous swapping added 30.12.95. Stephen Tweedie
	9	* Removed race in async swapping. 14.4.1996. Bruno Haible
	10	* Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
	11	* Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
	12	*/
	13
	14	#include <linux/mm.h>
	15	#include <linux/kernel_stat.h>
5a0e3ad6	16	#include <linux/gfp.h>
1da177e4 LT	17	#include <linux/pagemap.h>
	18	#include <linux/swap.h>
	19	#include <linux/bio.h>
	20	#include <linux/swapops.h>
62c230bc	21	#include <linux/buffer_head.h>
1da177e4	22	#include <linux/writeback.h>
38b5faf4	23	#include <linux/frontswap.h>
b430e9d1	24	#include <linux/blkdev.h>
e2e40f2c	25	#include <linux/uio.h>
b0ba2d0f	26	#include <linux/sched/task.h>
1da177e4 LT	27	#include <asm/pgtable.h>
1da177e4 LT	28
f29ad6a9	29	static struct bio *get_swap_bio(gfp_t gfp_flags,
1da177e4 LT	30	struct page *page, bio_end_io_t end_io)
	31	{
	32	struct bio *bio;
	33
1a5f439c	34	bio = bio_alloc(gfp_flags, 1);
1da177e4	35	if (bio) {
74d46992 CH	36	struct block_device *bdev;
	37
	38	bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
	39	bio_set_dev(bio, bdev);
4f024f37	40	bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
1da177e4	41	bio->bi_end_io = end_io;
6cf66b4c	42
1a5f439c	43	bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
1da177e4 LT	44	}
	45	return bio;
	46	}
	47
4246a0b6	48	void end_swap_bio_write(struct bio *bio)
1da177e4	49	{
263663cd	50	struct page *page = bio_first_page_all(bio);
1da177e4	51
4e4cbee9	52	if (bio->bi_status) {
1da177e4	53	SetPageError(page);
6ddab3b9 PZ	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);
1170532b	63	pr_alert("Write-error on swap-device (%u:%u:%llu)\n",
74d46992	64	MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
1170532b	65	(unsigned long long)bio->bi_iter.bi_sector);
6ddab3b9 PZ	66	ClearPageReclaim(page);
6ddab3b9 PZ	67	}
1da177e4 LT	68	end_page_writeback(page);
1da177e4 LT	69	bio_put(bio);
1da177e4 LT	70	}
1da177e4 LT	71
3f2b1a04 MK	72	static void swap_slot_free_notify(struct page *page)
	73	{
	74	struct swap_info_struct *sis;
	75	struct gendisk *disk;
5df373e9	76	swp_entry_t entry;
3f2b1a04 MK	77
	78	/*
	79	* There is no guarantee that the page is in swap cache - the software
	80	* suspend code (at least) uses end_swap_bio_read() against a non-
	81	* swapcache page. So we must check PG_swapcache before proceeding with
	82	* this optimization.
	83	*/
	84	if (unlikely(!PageSwapCache(page)))
	85	return;
	86
	87	sis = page_swap_info(page);
	88	if (!(sis->flags & SWP_BLKDEV))
	89	return;
	90
	91	/*
	92	* The swap subsystem performs lazy swap slot freeing,
	93	* expecting that the page will be swapped out again.
	94	* So we can avoid an unnecessary write if the page
	95	* isn't redirtied.
	96	* This is good for real swap storage because we can
	97	* reduce unnecessary I/O and enhance wear-leveling
	98	* if an SSD is used as the as swap device.
	99	* But if in-memory swap device (eg zram) is used,
	100	* this causes a duplicated copy between uncompressed
	101	* data in VM-owned memory and compressed data in
	102	* zram-owned memory. So let's free zram-owned memory
	103	* and make the VM-owned decompressed page dirty,
	104	* so the page should be swapped out somewhere again if
	105	* we again wish to reclaim it.
	106	*/
	107	disk = sis->bdev->bd_disk;
5df373e9 VM	108	entry.val = page_private(page);
5df373e9 VM	109	if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
3f2b1a04 MK	110	unsigned long offset;
3f2b1a04 MK	111
3f2b1a04 MK	112	offset = swp_offset(entry);
	113
	114	SetPageDirty(page);
	115	disk->fops->swap_slot_free_notify(sis->bdev,
	116	offset);
	117	}
	118	}
	119
4246a0b6	120	static void end_swap_bio_read(struct bio *bio)
1da177e4	121	{
263663cd	122	struct page *page = bio_first_page_all(bio);
23955622	123	struct task_struct *waiter = bio->bi_private;
1da177e4	124
4e4cbee9	125	if (bio->bi_status) {
1da177e4 LT	126	SetPageError(page);
1da177e4 LT	127	ClearPageUptodate(page);
1170532b	128	pr_alert("Read-error on swap-device (%u:%u:%llu)\n",
74d46992	129	MAJOR(bio_dev(bio)), MINOR(bio_dev(bio)),
1170532b	130	(unsigned long long)bio->bi_iter.bi_sector);
b430e9d1	131	goto out;
1da177e4	132	}
b430e9d1 MK	133
b430e9d1 MK	134	SetPageUptodate(page);
3f2b1a04	135	swap_slot_free_notify(page);
b430e9d1	136	out:
1da177e4	137	unlock_page(page);
23955622	138	WRITE_ONCE(bio->bi_private, NULL);
1da177e4	139	bio_put(bio);
87518530 ON	140	if (waiter) {
	141	blk_wake_io_task(waiter);
	142	put_task_struct(waiter);
	143	}
1da177e4 LT	144	}
1da177e4 LT	145
a509bc1a MG	146	int generic_swapfile_activate(struct swap_info_struct *sis,
	147	struct file *swap_file,
	148	sector_t *span)
	149	{
	150	struct address_space *mapping = swap_file->f_mapping;
	151	struct inode *inode = mapping->host;
	152	unsigned blocks_per_page;
	153	unsigned long page_no;
	154	unsigned blkbits;
	155	sector_t probe_block;
	156	sector_t last_block;
	157	sector_t lowest_block = -1;
	158	sector_t highest_block = 0;
	159	int nr_extents = 0;
	160	int ret;
	161
	162	blkbits = inode->i_blkbits;
	163	blocks_per_page = PAGE_SIZE >> blkbits;
	164
	165	/*
4efaceb1	166	* Map all the blocks into the extent tree. This code doesn't try
a509bc1a MG	167	* to be very smart.
	168	*/
	169	probe_block = 0;
	170	page_no = 0;
	171	last_block = i_size_read(inode) >> blkbits;
	172	while ((probe_block + blocks_per_page) <= last_block &&
	173	page_no < sis->max) {
	174	unsigned block_in_page;
	175	sector_t first_block;
	176
7e4411bf MP	177	cond_resched();
7e4411bf MP	178
a509bc1a MG	179	first_block = bmap(inode, probe_block);
	180	if (first_block == 0)
	181	goto bad_bmap;
	182
	183	/*
	184	* It must be PAGE_SIZE aligned on-disk
	185	*/
	186	if (first_block & (blocks_per_page - 1)) {
	187	probe_block++;
	188	goto reprobe;
	189	}
	190
	191	for (block_in_page = 1; block_in_page < blocks_per_page;
	192	block_in_page++) {
	193	sector_t block;
	194
	195	block = bmap(inode, probe_block + block_in_page);
	196	if (block == 0)
	197	goto bad_bmap;
	198	if (block != first_block + block_in_page) {
	199	/* Discontiguity */
	200	probe_block++;
	201	goto reprobe;
	202	}
	203	}
	204
	205	first_block >>= (PAGE_SHIFT - blkbits);
	206	if (page_no) { /* exclude the header page */
	207	if (first_block < lowest_block)
	208	lowest_block = first_block;
	209	if (first_block > highest_block)
	210	highest_block = first_block;
	211	}
	212
	213	/*
	214	* We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
	215	*/
	216	ret = add_swap_extent(sis, page_no, 1, first_block);
	217	if (ret < 0)
	218	goto out;
	219	nr_extents += ret;
	220	page_no++;
	221	probe_block += blocks_per_page;
	222	reprobe:
	223	continue;
	224	}
	225	ret = nr_extents;
	226	*span = 1 + highest_block - lowest_block;
	227	if (page_no == 0)
	228	page_no = 1; /* force Empty message */
	229	sis->max = page_no;
	230	sis->pages = page_no - 1;
	231	sis->highest_bit = page_no - 1;
	232	out:
	233	return ret;
	234	bad_bmap:
1170532b	235	pr_err("swapon: swapfile has holes\n");
a509bc1a MG	236	ret = -EINVAL;
	237	goto out;
	238	}
	239
1da177e4 LT	240	/*
	241	* We may have stale swap cache pages in memory: notice
	242	* them here and get rid of the unnecessary final write.
	243	*/
	244	int swap_writepage(struct page page, struct writeback_control wbc)
	245	{
2f772e6c	246	int ret = 0;
1da177e4	247
a2c43eed	248	if (try_to_free_swap(page)) {
1da177e4 LT	249	unlock_page(page);
	250	goto out;
	251	}
165c8aed	252	if (frontswap_store(page) == 0) {
38b5faf4 DM	253	set_page_writeback(page);
	254	unlock_page(page);
	255	end_page_writeback(page);
	256	goto out;
	257	}
1eec6702	258	ret = __swap_writepage(page, wbc, end_swap_bio_write);
2f772e6c SJ	259	out:
	260	return ret;
	261	}
	262
225311a4 HY	263	static inline void count_swpout_vm_event(struct page *page)
	264	{
	265	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	266	if (unlikely(PageTransHuge(page)))
	267	count_vm_event(THP_SWPOUT);
	268	#endif
	269	count_vm_events(PSWPOUT, hpage_nr_pages(page));
	270	}
	271
1eec6702	272	int __swap_writepage(struct page page, struct writeback_control wbc,
4246a0b6	273	bio_end_io_t end_write_func)
2f772e6c SJ	274	{
2f772e6c SJ	275	struct bio *bio;
4e49ea4a	276	int ret;
2f772e6c	277	struct swap_info_struct *sis = page_swap_info(page);
62c230bc	278
cc30c5d6	279	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
bc4ae27d	280	if (sis->flags & SWP_FS) {
62c230bc MG	281	struct kiocb kiocb;
	282	struct file *swap_file = sis->swap_file;
	283	struct address_space *mapping = swap_file->f_mapping;
62a8067a AV	284	struct bio_vec bv = {
	285	.bv_page = page,
	286	.bv_len = PAGE_SIZE,
	287	.bv_offset = 0
	288	};
05afcb77	289	struct iov_iter from;
62c230bc	290
aa563d7b	291	iov_iter_bvec(&from, WRITE, &bv, 1, PAGE_SIZE);
62c230bc MG	292	init_sync_kiocb(&kiocb, swap_file);
62c230bc MG	293	kiocb.ki_pos = page_file_offset(page);
62c230bc	294
0cdc444a	295	set_page_writeback(page);
62c230bc	296	unlock_page(page);
c8b8e32d	297	ret = mapping->a_ops->direct_IO(&kiocb, &from);
62c230bc MG	298	if (ret == PAGE_SIZE) {
	299	count_vm_event(PSWPOUT);
	300	ret = 0;
2d30d31e	301	} else {
0cdc444a MG	302	/*
	303	* In the case of swap-over-nfs, this can be a
	304	* temporary failure if the system has limited
	305	* memory for allocating transmit buffers.
	306	* Mark the page dirty and avoid
	307	* rotate_reclaimable_page but rate-limit the
	308	* messages but do not flag PageError like
	309	* the normal direct-to-bio case as it could
	310	* be temporary.
	311	*/
2d30d31e	312	set_page_dirty(page);
0cdc444a	313	ClearPageReclaim(page);
1170532b JP	314	pr_err_ratelimited("Write error on dio swapfile (%llu)\n",
1170532b JP	315	page_file_offset(page));
62c230bc	316	}
0cdc444a	317	end_page_writeback(page);
62c230bc MG	318	return ret;
	319	}
	320
dd6bd0d9 MW	321	ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
dd6bd0d9 MW	322	if (!ret) {
225311a4	323	count_swpout_vm_event(page);
dd6bd0d9 MW	324	return 0;
	325	}
	326
	327	ret = 0;
1eec6702	328	bio = get_swap_bio(GFP_NOIO, page, end_write_func);
1da177e4 LT	329	if (bio == NULL) {
	330	set_page_dirty(page);
	331	unlock_page(page);
	332	ret = -ENOMEM;
	333	goto out;
	334	}
0d1e0c7c	335	bio->bi_opf = REQ_OP_WRITE \| REQ_SWAP \| wbc_to_write_flags(wbc);
6a7f6d86	336	bio_associate_blkg_from_page(bio, page);
225311a4	337	count_swpout_vm_event(page);
1da177e4 LT	338	set_page_writeback(page);
1da177e4 LT	339	unlock_page(page);
4e49ea4a	340	submit_bio(bio);
1da177e4 LT	341	out:
	342	return ret;
	343	}
	344
0bcac06f	345	int swap_readpage(struct page *page, bool synchronous)
1da177e4 LT	346	{
	347	struct bio *bio;
	348	int ret = 0;
62c230bc	349	struct swap_info_struct *sis = page_swap_info(page);
23955622	350	blk_qc_t qc;
74d46992	351	struct gendisk *disk;
1da177e4	352
0bcac06f	353	VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
309381fe SL	354	VM_BUG_ON_PAGE(!PageLocked(page), page);
309381fe SL	355	VM_BUG_ON_PAGE(PageUptodate(page), page);
165c8aed	356	if (frontswap_load(page) == 0) {
38b5faf4 DM	357	SetPageUptodate(page);
	358	unlock_page(page);
	359	goto out;
	360	}
62c230bc	361
bc4ae27d	362	if (sis->flags & SWP_FS) {
62c230bc MG	363	struct file *swap_file = sis->swap_file;
	364	struct address_space *mapping = swap_file->f_mapping;
	365
	366	ret = mapping->a_ops->readpage(swap_file, page);
	367	if (!ret)
	368	count_vm_event(PSWPIN);
	369	return ret;
	370	}
	371
dd6bd0d9 MW	372	ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
dd6bd0d9 MW	373	if (!ret) {
b06bad17 MK	374	if (trylock_page(page)) {
	375	swap_slot_free_notify(page);
	376	unlock_page(page);
	377	}
	378
dd6bd0d9 MW	379	count_vm_event(PSWPIN);
	380	return 0;
	381	}
	382
	383	ret = 0;
f29ad6a9	384	bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
1da177e4 LT	385	if (bio == NULL) {
	386	unlock_page(page);
	387	ret = -ENOMEM;
	388	goto out;
	389	}
74d46992	390	disk = bio->bi_disk;
b0ba2d0f TH	391	/*
	392	* Keep this task valid during swap readpage because the oom killer may
	393	* attempt to access it in the page fault retry time check.
	394	*/
95fe6c1a	395	bio_set_op_attrs(bio, REQ_OP_READ, 0);
87518530	396	if (synchronous) {
b685a735	397	bio->bi_opf \|= REQ_HIPRI;
87518530 ON	398	get_task_struct(current);
	399	bio->bi_private = current;
	400	}
f8891e5e	401	count_vm_event(PSWPIN);
23955622 SL	402	bio_get(bio);
23955622 SL	403	qc = submit_bio(bio);
0bcac06f	404	while (synchronous) {
1ac5cd49	405	set_current_state(TASK_UNINTERRUPTIBLE);
23955622 SL	406	if (!READ_ONCE(bio->bi_private))
	407	break;
	408
0a1b8b87	409	if (!blk_poll(disk->queue, qc, true))
b685a735	410	io_schedule();
23955622 SL	411	}
	412	__set_current_state(TASK_RUNNING);
	413	bio_put(bio);
	414
1da177e4 LT	415	out:
	416	return ret;
	417	}
62c230bc MG	418
	419	int swap_set_page_dirty(struct page *page)
	420	{
	421	struct swap_info_struct *sis = page_swap_info(page);
	422
bc4ae27d	423	if (sis->flags & SWP_FS) {
62c230bc	424	struct address_space *mapping = sis->swap_file->f_mapping;
cc30c5d6 AM	425
cc30c5d6 AM	426	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
62c230bc MG	427	return mapping->a_ops->set_page_dirty(page);
	428	} else {
	429	return __set_page_dirty_no_writeback(page);
	430	}
	431	}