mm/page_io.c - linux/kernel/git/will/linux - Git at Google

 // 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/writeback.h>
 #include <linux/blkdev.h>
 #include <linux/psi.h>
 #include <linux/uio.h>
 #include <linux/sched/task.h>
 #include <linux/delayacct.h>
 #include <linux/zswap.h>
 #include "swap.h"

 static void __end_swap_bio_write(struct bio *bio)
 {
 	struct folio *folio = bio_first_folio_all(bio);

 	if (bio->bi_status) {
 		/*
 		 * 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 folio_rotate_reclaimable()
 		 */
 		folio_mark_dirty(folio);
 		pr_alert_ratelimited("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);
 		folio_clear_reclaim(folio);
 	}
 	folio_end_writeback(folio);
 }

 static void end_swap_bio_write(struct bio *bio)
 {
 	__end_swap_bio_write(bio);
 	bio_put(bio);
 }

 static void __end_swap_bio_read(struct bio *bio)
 {
 	struct folio *folio = bio_first_folio_all(bio);

 	if (bio->bi_status) {
 		pr_alert_ratelimited("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);
 	} else {
 		folio_mark_uptodate(folio);
 	}
 	folio_unlock(folio);
 }

 static void end_swap_bio_read(struct bio *bio)
 {
 	__end_swap_bio_read(bio);
 	bio_put(bio);
 }

 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 = probe_block;
 		ret = bmap(inode, &first_block);
 		if (ret || !first_block)
 			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 = probe_block + block_in_page;
 			ret = bmap(inode, &block);
 			if (ret || !block)
 				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)
 {
 	struct folio *folio = page_folio(page);
 	int ret;

 	if (folio_free_swap(folio)) {
 		folio_unlock(folio);
 		return 0;
 	}
 	/*
 	 * Arch code may have to preserve more data than just the page
 	 * contents, e.g. memory tags.
 	 */
 	ret = arch_prepare_to_swap(&folio->page);
 	if (ret) {
 		folio_mark_dirty(folio);
 		folio_unlock(folio);
 		return ret;
 	}
 	if (zswap_store(folio)) {
 		folio_start_writeback(folio);
 		folio_unlock(folio);
 		folio_end_writeback(folio);
 		return 0;
 	}
 	if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
 		folio_mark_dirty(folio);
 		return AOP_WRITEPAGE_ACTIVATE;
 	}

 	__swap_writepage(folio, wbc);
 	return 0;
 }

 static inline void count_swpout_vm_event(struct folio *folio)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	if (unlikely(folio_test_pmd_mappable(folio))) {
 		count_memcg_folio_events(folio, THP_SWPOUT, 1);
 		count_vm_event(THP_SWPOUT);
 	}
 #endif
 	count_vm_events(PSWPOUT, folio_nr_pages(folio));
 }

 #if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
 static void bio_associate_blkg_from_page(struct bio *bio, struct folio *folio)
 {
 	struct cgroup_subsys_state *css;
 	struct mem_cgroup *memcg;

 	memcg = folio_memcg(folio);
 	if (!memcg)
 		return;

 	rcu_read_lock();
 	css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
 	bio_associate_blkg_from_css(bio, css);
 	rcu_read_unlock();
 }
 #else
 #define bio_associate_blkg_from_page(bio, folio)		do { } while (0)
 #endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */

 struct swap_iocb {
 	struct kiocb		iocb;
 	struct bio_vec		bvec[SWAP_CLUSTER_MAX];
 	int			pages;
 	int			len;
 };
 static mempool_t *sio_pool;

 int sio_pool_init(void)
 {
 	if (!sio_pool) {
 		mempool_t *pool = mempool_create_kmalloc_pool(
 			SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
 		if (cmpxchg(&sio_pool, NULL, pool))
 			mempool_destroy(pool);
 	}
 	if (!sio_pool)
 		return -ENOMEM;
 	return 0;
 }

 static void sio_write_complete(struct kiocb *iocb, long ret)
 {
 	struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
 	struct page *page = sio->bvec[0].bv_page;
 	int p;

 	if (ret != sio->len) {
 		/*
 		 * 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
 		 * folio_rotate_reclaimable but rate-limit the
 		 * messages but do not flag PageError like
 		 * the normal direct-to-bio case as it could
 		 * be temporary.
 		 */
 		pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
 				   ret, page_file_offset(page));
 		for (p = 0; p < sio->pages; p++) {
 			page = sio->bvec[p].bv_page;
 			set_page_dirty(page);
 			ClearPageReclaim(page);
 		}
 	}

 	for (p = 0; p < sio->pages; p++)
 		end_page_writeback(sio->bvec[p].bv_page);

 	mempool_free(sio, sio_pool);
 }

 static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc)
 {
 	struct swap_iocb *sio = NULL;
 	struct swap_info_struct *sis = swp_swap_info(folio->swap);
 	struct file *swap_file = sis->swap_file;
 	loff_t pos = folio_file_pos(folio);

 	count_swpout_vm_event(folio);
 	folio_start_writeback(folio);
 	folio_unlock(folio);
 	if (wbc->swap_plug)
 		sio = *wbc->swap_plug;
 	if (sio) {
 		if (sio->iocb.ki_filp != swap_file ||
 		    sio->iocb.ki_pos + sio->len != pos) {
 			swap_write_unplug(sio);
 			sio = NULL;
 		}
 	}
 	if (!sio) {
 		sio = mempool_alloc(sio_pool, GFP_NOIO);
 		init_sync_kiocb(&sio->iocb, swap_file);
 		sio->iocb.ki_complete = sio_write_complete;
 		sio->iocb.ki_pos = pos;
 		sio->pages = 0;
 		sio->len = 0;
 	}
 	bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
 	sio->len += folio_size(folio);
 	sio->pages += 1;
 	if (sio->pages == ARRAY_SIZE(sio->bvec) || !wbc->swap_plug) {
 		swap_write_unplug(sio);
 		sio = NULL;
 	}
 	if (wbc->swap_plug)
 		*wbc->swap_plug = sio;
 }

 static void swap_writepage_bdev_sync(struct folio *folio,
 		struct writeback_control *wbc, struct swap_info_struct *sis)
 {
 	struct bio_vec bv;
 	struct bio bio;

 	bio_init(&bio, sis->bdev, &bv, 1,
 		 REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc));
 	bio.bi_iter.bi_sector = swap_folio_sector(folio);
 	bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);

 	bio_associate_blkg_from_page(&bio, folio);
 	count_swpout_vm_event(folio);

 	folio_start_writeback(folio);
 	folio_unlock(folio);

 	submit_bio_wait(&bio);
 	__end_swap_bio_write(&bio);
 }

 static void swap_writepage_bdev_async(struct folio *folio,
 		struct writeback_control *wbc, struct swap_info_struct *sis)
 {
 	struct bio *bio;

 	bio = bio_alloc(sis->bdev, 1,
 			REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
 			GFP_NOIO);
 	bio->bi_iter.bi_sector = swap_folio_sector(folio);
 	bio->bi_end_io = end_swap_bio_write;
 	bio_add_folio_nofail(bio, folio, folio_size(folio), 0);

 	bio_associate_blkg_from_page(bio, folio);
 	count_swpout_vm_event(folio);
 	folio_start_writeback(folio);
 	folio_unlock(folio);
 	submit_bio(bio);
 }

 void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
 {
 	struct swap_info_struct *sis = swp_swap_info(folio->swap);

 	VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
 	/*
 	 * ->flags can be updated non-atomicially (scan_swap_map_slots),
 	 * but that will never affect SWP_FS_OPS, so the data_race
 	 * is safe.
 	 */
 	if (data_race(sis->flags & SWP_FS_OPS))
 		swap_writepage_fs(folio, wbc);
 	else if (sis->flags & SWP_SYNCHRONOUS_IO)
 		swap_writepage_bdev_sync(folio, wbc, sis);
 	else
 		swap_writepage_bdev_async(folio, wbc, sis);
 }

 void swap_write_unplug(struct swap_iocb *sio)
 {
 	struct iov_iter from;
 	struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
 	int ret;

 	iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
 	ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
 	if (ret != -EIOCBQUEUED)
 		sio_write_complete(&sio->iocb, ret);
 }

 static void sio_read_complete(struct kiocb *iocb, long ret)
 {
 	struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
 	int p;

 	if (ret == sio->len) {
 		for (p = 0; p < sio->pages; p++) {
 			struct folio *folio = page_folio(sio->bvec[p].bv_page);

 			folio_mark_uptodate(folio);
 			folio_unlock(folio);
 		}
 		count_vm_events(PSWPIN, sio->pages);
 	} else {
 		for (p = 0; p < sio->pages; p++) {
 			struct folio *folio = page_folio(sio->bvec[p].bv_page);

 			folio_unlock(folio);
 		}
 		pr_alert_ratelimited("Read-error on swap-device\n");
 	}
 	mempool_free(sio, sio_pool);
 }

 static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug)
 {
 	struct swap_info_struct *sis = swp_swap_info(folio->swap);
 	struct swap_iocb *sio = NULL;
 	loff_t pos = folio_file_pos(folio);

 	if (plug)
 		sio = *plug;
 	if (sio) {
 		if (sio->iocb.ki_filp != sis->swap_file ||
 		    sio->iocb.ki_pos + sio->len != pos) {
 			swap_read_unplug(sio);
 			sio = NULL;
 		}
 	}
 	if (!sio) {
 		sio = mempool_alloc(sio_pool, GFP_KERNEL);
 		init_sync_kiocb(&sio->iocb, sis->swap_file);
 		sio->iocb.ki_pos = pos;
 		sio->iocb.ki_complete = sio_read_complete;
 		sio->pages = 0;
 		sio->len = 0;
 	}
 	bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
 	sio->len += folio_size(folio);
 	sio->pages += 1;
 	if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
 		swap_read_unplug(sio);
 		sio = NULL;
 	}
 	if (plug)
 		*plug = sio;
 }

 static void swap_read_folio_bdev_sync(struct folio *folio,
 		struct swap_info_struct *sis)
 {
 	struct bio_vec bv;
 	struct bio bio;

 	bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
 	bio.bi_iter.bi_sector = swap_folio_sector(folio);
 	bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
 	/*
 	 * Keep this task valid during swap readpage because the oom killer may
 	 * attempt to access it in the page fault retry time check.
 	 */
 	get_task_struct(current);
 	count_vm_event(PSWPIN);
 	submit_bio_wait(&bio);
 	__end_swap_bio_read(&bio);
 	put_task_struct(current);
 }

 static void swap_read_folio_bdev_async(struct folio *folio,
 		struct swap_info_struct *sis)
 {
 	struct bio *bio;

 	bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
 	bio->bi_iter.bi_sector = swap_folio_sector(folio);
 	bio->bi_end_io = end_swap_bio_read;
 	bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
 	count_vm_event(PSWPIN);
 	submit_bio(bio);
 }

 void swap_read_folio(struct folio *folio, bool synchronous,
 		struct swap_iocb **plug)
 {
 	struct swap_info_struct *sis = swp_swap_info(folio->swap);
 	bool workingset = folio_test_workingset(folio);
 	unsigned long pflags;
 	bool in_thrashing;

 	VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
 	VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);

 	/*
 	 * Count submission time as memory stall and delay. When the device
 	 * is congested, or the submitting cgroup IO-throttled, submission
 	 * can be a significant part of overall IO time.
 	 */
 	if (workingset) {
 		delayacct_thrashing_start(&in_thrashing);
 		psi_memstall_enter(&pflags);
 	}
 	delayacct_swapin_start();

 	if (zswap_load(folio)) {
 		folio_mark_uptodate(folio);
 		folio_unlock(folio);
 	} else if (data_race(sis->flags & SWP_FS_OPS)) {
 		swap_read_folio_fs(folio, plug);
 	} else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) {
 		swap_read_folio_bdev_sync(folio, sis);
 	} else {
 		swap_read_folio_bdev_async(folio, sis);
 	}

 	if (workingset) {
 		delayacct_thrashing_end(&in_thrashing);
 		psi_memstall_leave(&pflags);
 	}
 	delayacct_swapin_end();
 }

 void __swap_read_unplug(struct swap_iocb *sio)
 {
 	struct iov_iter from;
 	struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
 	int ret;

 	iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
 	ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
 	if (ret != -EIOCBQUEUED)
 		sio_read_complete(&sio->iocb, ret);
 }
	// 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/writeback.h>
	#include <linux/blkdev.h>
	#include <linux/psi.h>
	#include <linux/uio.h>
	#include <linux/sched/task.h>
	#include <linux/delayacct.h>
	#include <linux/zswap.h>
	#include "swap.h"

	static void __end_swap_bio_write(struct bio *bio)
	{
	struct folio *folio = bio_first_folio_all(bio);

	if (bio->bi_status) {
	/*
	* 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 folio_rotate_reclaimable()
	*/
	folio_mark_dirty(folio);
	pr_alert_ratelimited("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);
	folio_clear_reclaim(folio);
	}
	folio_end_writeback(folio);
	}

	static void end_swap_bio_write(struct bio *bio)
	{
	__end_swap_bio_write(bio);
	bio_put(bio);
	}

	static void __end_swap_bio_read(struct bio *bio)
	{
	struct folio *folio = bio_first_folio_all(bio);

	if (bio->bi_status) {
	pr_alert_ratelimited("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);
	} else {
	folio_mark_uptodate(folio);
	}
	folio_unlock(folio);
	}

	static void end_swap_bio_read(struct bio *bio)
	{
	__end_swap_bio_read(bio);
	bio_put(bio);
	}

	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 = probe_block;
	ret = bmap(inode, &first_block);
	if (ret \|\| !first_block)
	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 = probe_block + block_in_page;
	ret = bmap(inode, &block);
	if (ret \|\| !block)
	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)
	{
	struct folio *folio = page_folio(page);
	int ret;

	if (folio_free_swap(folio)) {
	folio_unlock(folio);
	return 0;
	}
	/*
	* Arch code may have to preserve more data than just the page
	* contents, e.g. memory tags.
	*/
	ret = arch_prepare_to_swap(&folio->page);
	if (ret) {
	folio_mark_dirty(folio);
	folio_unlock(folio);
	return ret;
	}
	if (zswap_store(folio)) {
	folio_start_writeback(folio);
	folio_unlock(folio);
	folio_end_writeback(folio);
	return 0;
	}
	if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) {
	folio_mark_dirty(folio);
	return AOP_WRITEPAGE_ACTIVATE;
	}

	__swap_writepage(folio, wbc);
	return 0;
	}

	static inline void count_swpout_vm_event(struct folio *folio)
	{
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	if (unlikely(folio_test_pmd_mappable(folio))) {
	count_memcg_folio_events(folio, THP_SWPOUT, 1);
	count_vm_event(THP_SWPOUT);
	}
	#endif
	count_vm_events(PSWPOUT, folio_nr_pages(folio));
	}

	#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
	static void bio_associate_blkg_from_page(struct bio bio, struct folio folio)
	{
	struct cgroup_subsys_state *css;
	struct mem_cgroup *memcg;

	memcg = folio_memcg(folio);
	if (!memcg)
	return;

	rcu_read_lock();
	css = cgroup_e_css(memcg->css.cgroup, &io_cgrp_subsys);
	bio_associate_blkg_from_css(bio, css);
	rcu_read_unlock();
	}
	#else
	#define bio_associate_blkg_from_page(bio, folio) do { } while (0)
	#endif /* CONFIG_MEMCG && CONFIG_BLK_CGROUP */

	struct swap_iocb {
	struct kiocb iocb;
	struct bio_vec bvec[SWAP_CLUSTER_MAX];
	int pages;
	int len;
	};
	static mempool_t *sio_pool;

	int sio_pool_init(void)
	{
	if (!sio_pool) {
	mempool_t *pool = mempool_create_kmalloc_pool(
	SWAP_CLUSTER_MAX, sizeof(struct swap_iocb));
	if (cmpxchg(&sio_pool, NULL, pool))
	mempool_destroy(pool);
	}
	if (!sio_pool)
	return -ENOMEM;
	return 0;
	}

	static void sio_write_complete(struct kiocb *iocb, long ret)
	{
	struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
	struct page *page = sio->bvec[0].bv_page;
	int p;

	if (ret != sio->len) {
	/*
	* 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
	* folio_rotate_reclaimable but rate-limit the
	* messages but do not flag PageError like
	* the normal direct-to-bio case as it could
	* be temporary.
	*/
	pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n",
	ret, page_file_offset(page));
	for (p = 0; p < sio->pages; p++) {
	page = sio->bvec[p].bv_page;
	set_page_dirty(page);
	ClearPageReclaim(page);
	}
	}

	for (p = 0; p < sio->pages; p++)
	end_page_writeback(sio->bvec[p].bv_page);

	mempool_free(sio, sio_pool);
	}

	static void swap_writepage_fs(struct folio folio, struct writeback_control wbc)
	{
	struct swap_iocb *sio = NULL;
	struct swap_info_struct *sis = swp_swap_info(folio->swap);
	struct file *swap_file = sis->swap_file;
	loff_t pos = folio_file_pos(folio);

	count_swpout_vm_event(folio);
	folio_start_writeback(folio);
	folio_unlock(folio);
	if (wbc->swap_plug)
	sio = *wbc->swap_plug;
	if (sio) {
	if (sio->iocb.ki_filp != swap_file \|\|
	sio->iocb.ki_pos + sio->len != pos) {
	swap_write_unplug(sio);
	sio = NULL;
	}
	}
	if (!sio) {
	sio = mempool_alloc(sio_pool, GFP_NOIO);
	init_sync_kiocb(&sio->iocb, swap_file);
	sio->iocb.ki_complete = sio_write_complete;
	sio->iocb.ki_pos = pos;
	sio->pages = 0;
	sio->len = 0;
	}
	bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
	sio->len += folio_size(folio);
	sio->pages += 1;
	if (sio->pages == ARRAY_SIZE(sio->bvec) \|\| !wbc->swap_plug) {
	swap_write_unplug(sio);
	sio = NULL;
	}
	if (wbc->swap_plug)
	*wbc->swap_plug = sio;
	}

	static void swap_writepage_bdev_sync(struct folio *folio,
	struct writeback_control wbc, struct swap_info_struct sis)
	{
	struct bio_vec bv;
	struct bio bio;

	bio_init(&bio, sis->bdev, &bv, 1,
	REQ_OP_WRITE \| REQ_SWAP \| wbc_to_write_flags(wbc));
	bio.bi_iter.bi_sector = swap_folio_sector(folio);
	bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);

	bio_associate_blkg_from_page(&bio, folio);
	count_swpout_vm_event(folio);

	folio_start_writeback(folio);
	folio_unlock(folio);

	submit_bio_wait(&bio);
	__end_swap_bio_write(&bio);
	}

	static void swap_writepage_bdev_async(struct folio *folio,
	struct writeback_control wbc, struct swap_info_struct sis)
	{
	struct bio *bio;

	bio = bio_alloc(sis->bdev, 1,
	REQ_OP_WRITE \| REQ_SWAP \| wbc_to_write_flags(wbc),
	GFP_NOIO);
	bio->bi_iter.bi_sector = swap_folio_sector(folio);
	bio->bi_end_io = end_swap_bio_write;
	bio_add_folio_nofail(bio, folio, folio_size(folio), 0);

	bio_associate_blkg_from_page(bio, folio);
	count_swpout_vm_event(folio);
	folio_start_writeback(folio);
	folio_unlock(folio);
	submit_bio(bio);
	}

	void __swap_writepage(struct folio folio, struct writeback_control wbc)
	{
	struct swap_info_struct *sis = swp_swap_info(folio->swap);

	VM_BUG_ON_FOLIO(!folio_test_swapcache(folio), folio);
	/*
	* ->flags can be updated non-atomicially (scan_swap_map_slots),
	* but that will never affect SWP_FS_OPS, so the data_race
	* is safe.
	*/
	if (data_race(sis->flags & SWP_FS_OPS))
	swap_writepage_fs(folio, wbc);
	else if (sis->flags & SWP_SYNCHRONOUS_IO)
	swap_writepage_bdev_sync(folio, wbc, sis);
	else
	swap_writepage_bdev_async(folio, wbc, sis);
	}

	void swap_write_unplug(struct swap_iocb *sio)
	{
	struct iov_iter from;
	struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
	int ret;

	iov_iter_bvec(&from, ITER_SOURCE, sio->bvec, sio->pages, sio->len);
	ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
	if (ret != -EIOCBQUEUED)
	sio_write_complete(&sio->iocb, ret);
	}

	static void sio_read_complete(struct kiocb *iocb, long ret)
	{
	struct swap_iocb *sio = container_of(iocb, struct swap_iocb, iocb);
	int p;

	if (ret == sio->len) {
	for (p = 0; p < sio->pages; p++) {
	struct folio *folio = page_folio(sio->bvec[p].bv_page);

	folio_mark_uptodate(folio);
	folio_unlock(folio);
	}
	count_vm_events(PSWPIN, sio->pages);
	} else {
	for (p = 0; p < sio->pages; p++) {
	struct folio *folio = page_folio(sio->bvec[p].bv_page);

	folio_unlock(folio);
	}
	pr_alert_ratelimited("Read-error on swap-device\n");
	}
	mempool_free(sio, sio_pool);
	}

	static void swap_read_folio_fs(struct folio folio, struct swap_iocb *plug)
	{
	struct swap_info_struct *sis = swp_swap_info(folio->swap);
	struct swap_iocb *sio = NULL;
	loff_t pos = folio_file_pos(folio);

	if (plug)
	sio = *plug;
	if (sio) {
	if (sio->iocb.ki_filp != sis->swap_file \|\|
	sio->iocb.ki_pos + sio->len != pos) {
	swap_read_unplug(sio);
	sio = NULL;
	}
	}
	if (!sio) {
	sio = mempool_alloc(sio_pool, GFP_KERNEL);
	init_sync_kiocb(&sio->iocb, sis->swap_file);
	sio->iocb.ki_pos = pos;
	sio->iocb.ki_complete = sio_read_complete;
	sio->pages = 0;
	sio->len = 0;
	}
	bvec_set_folio(&sio->bvec[sio->pages], folio, folio_size(folio), 0);
	sio->len += folio_size(folio);
	sio->pages += 1;
	if (sio->pages == ARRAY_SIZE(sio->bvec) \|\| !plug) {
	swap_read_unplug(sio);
	sio = NULL;
	}
	if (plug)
	*plug = sio;
	}

	static void swap_read_folio_bdev_sync(struct folio *folio,
	struct swap_info_struct *sis)
	{
	struct bio_vec bv;
	struct bio bio;

	bio_init(&bio, sis->bdev, &bv, 1, REQ_OP_READ);
	bio.bi_iter.bi_sector = swap_folio_sector(folio);
	bio_add_folio_nofail(&bio, folio, folio_size(folio), 0);
	/*
	* Keep this task valid during swap readpage because the oom killer may
	* attempt to access it in the page fault retry time check.
	*/
	get_task_struct(current);
	count_vm_event(PSWPIN);
	submit_bio_wait(&bio);
	__end_swap_bio_read(&bio);
	put_task_struct(current);
	}

	static void swap_read_folio_bdev_async(struct folio *folio,
	struct swap_info_struct *sis)
	{
	struct bio *bio;

	bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
	bio->bi_iter.bi_sector = swap_folio_sector(folio);
	bio->bi_end_io = end_swap_bio_read;
	bio_add_folio_nofail(bio, folio, folio_size(folio), 0);
	count_vm_event(PSWPIN);
	submit_bio(bio);
	}

	void swap_read_folio(struct folio *folio, bool synchronous,
	struct swap_iocb **plug)
	{
	struct swap_info_struct *sis = swp_swap_info(folio->swap);
	bool workingset = folio_test_workingset(folio);
	unsigned long pflags;
	bool in_thrashing;

	VM_BUG_ON_FOLIO(!folio_test_swapcache(folio) && !synchronous, folio);
	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
	VM_BUG_ON_FOLIO(folio_test_uptodate(folio), folio);

	/*
	* Count submission time as memory stall and delay. When the device
	* is congested, or the submitting cgroup IO-throttled, submission
	* can be a significant part of overall IO time.
	*/
	if (workingset) {
	delayacct_thrashing_start(&in_thrashing);
	psi_memstall_enter(&pflags);
	}
	delayacct_swapin_start();

	if (zswap_load(folio)) {
	folio_mark_uptodate(folio);
	folio_unlock(folio);
	} else if (data_race(sis->flags & SWP_FS_OPS)) {
	swap_read_folio_fs(folio, plug);
	} else if (synchronous \|\| (sis->flags & SWP_SYNCHRONOUS_IO)) {
	swap_read_folio_bdev_sync(folio, sis);
	} else {
	swap_read_folio_bdev_async(folio, sis);
	}

	if (workingset) {
	delayacct_thrashing_end(&in_thrashing);
	psi_memstall_leave(&pflags);
	}
	delayacct_swapin_end();
	}

	void __swap_read_unplug(struct swap_iocb *sio)
	{
	struct iov_iter from;
	struct address_space *mapping = sio->iocb.ki_filp->f_mapping;
	int ret;

	iov_iter_bvec(&from, ITER_DEST, sio->bvec, sio->pages, sio->len);
	ret = mapping->a_ops->swap_rw(&sio->iocb, &from);
	if (ret != -EIOCBQUEUED)
	sio_read_complete(&sio->iocb, ret);
	}