1 files changed, 537 insertions, 0 deletions

diff --git a/mm/page_io.c b/mm/page_io.c
new file mode 100644
index 000000000..3a5f921b9
--- /dev/null
+++ b/mm/page_io.c
@@ -0,0 +1,537 @@
+// 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/psi.h>
+#include <linux/uio.h>
+#include <linux/sched/task.h>
+#include <linux/delayacct.h>
+#include "swap.h"
+
+static 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 folio_rotate_reclaimable()
+		 */
+		set_page_dirty(page);
+		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);
+		ClearPageReclaim(page);
+	}
+	end_page_writeback(page);
+	bio_put(bio);
+}
+
+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_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);
+		goto out;
+	}
+
+	SetPageUptodate(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 = 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 = 0;
+
+	if (folio_free_swap(folio)) {
+		folio_unlock(folio);
+		goto out;
+	}
+	/*
+	 * 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);
+		goto out;
+	}
+	if (frontswap_store(&folio->page) == 0) {
+		folio_start_writeback(folio);
+		folio_unlock(folio);
+		folio_end_writeback(folio);
+		goto out;
+	}
+	ret = __swap_writepage(&folio->page, wbc);
+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, thp_nr_pages(page));
+}
+
+#if defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)
+static void bio_associate_blkg_from_page(struct bio *bio, struct page *page)
+{
+	struct cgroup_subsys_state *css;
+	struct mem_cgroup *memcg;
+
+	memcg = page_memcg(page);
+	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, page)		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);
+		}
+	} else {
+		for (p = 0; p < sio->pages; p++)
+			count_swpout_vm_event(sio->bvec[p].bv_page);
+	}
+
+	for (p = 0; p < sio->pages; p++)
+		end_page_writeback(sio->bvec[p].bv_page);
+
+	mempool_free(sio, sio_pool);
+}
+
+static int swap_writepage_fs(struct page *page, struct writeback_control *wbc)
+{
+	struct swap_iocb *sio = NULL;
+	struct swap_info_struct *sis = page_swap_info(page);
+	struct file *swap_file = sis->swap_file;
+	loff_t pos = page_file_offset(page);
+
+	set_page_writeback(page);
+	unlock_page(page);
+	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;
+	}
+	sio->bvec[sio->pages].bv_page = page;
+	sio->bvec[sio->pages].bv_len = thp_size(page);
+	sio->bvec[sio->pages].bv_offset = 0;
+	sio->len += thp_size(page);
+	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;
+
+	return 0;
+}
+
+int __swap_writepage(struct page *page, struct writeback_control *wbc)
+{
+	struct bio *bio;
+	int ret;
+	struct swap_info_struct *sis = page_swap_info(page);
+
+	VM_BUG_ON_PAGE(!PageSwapCache(page), page);
+	/*
+	 * ->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))
+		return swap_writepage_fs(page, wbc);
+
+	ret = bdev_write_page(sis->bdev, swap_page_sector(page), page, wbc);
+	if (!ret) {
+		count_swpout_vm_event(page);
+		return 0;
+	}
+
+	bio = bio_alloc(sis->bdev, 1,
+			REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc),
+			GFP_NOIO);
+	bio->bi_iter.bi_sector = swap_page_sector(page);
+	bio->bi_end_io = end_swap_bio_write;
+	bio_add_page(bio, page, thp_size(page), 0);
+
+	bio_associate_blkg_from_page(bio, page);
+	count_swpout_vm_event(page);
+	set_page_writeback(page);
+	unlock_page(page);
+	submit_bio(bio);
+
+	return 0;
+}
+
+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 page *page = sio->bvec[p].bv_page;
+
+			SetPageUptodate(page);
+			unlock_page(page);
+		}
+		count_vm_events(PSWPIN, sio->pages);
+	} else {
+		for (p = 0; p < sio->pages; p++) {
+			struct page *page = sio->bvec[p].bv_page;
+
+			SetPageError(page);
+			ClearPageUptodate(page);
+			unlock_page(page);
+		}
+		pr_alert_ratelimited("Read-error on swap-device\n");
+	}
+	mempool_free(sio, sio_pool);
+}
+
+static void swap_readpage_fs(struct page *page,
+			     struct swap_iocb **plug)
+{
+	struct swap_info_struct *sis = page_swap_info(page);
+	struct swap_iocb *sio = NULL;
+	loff_t pos = page_file_offset(page);
+
+	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;
+	}
+	sio->bvec[sio->pages].bv_page = page;
+	sio->bvec[sio->pages].bv_len = thp_size(page);
+	sio->bvec[sio->pages].bv_offset = 0;
+	sio->len += thp_size(page);
+	sio->pages += 1;
+	if (sio->pages == ARRAY_SIZE(sio->bvec) || !plug) {
+		swap_read_unplug(sio);
+		sio = NULL;
+	}
+	if (plug)
+		*plug = sio;
+}
+
+int swap_readpage(struct page *page, bool synchronous,
+		  struct swap_iocb **plug)
+{
+	struct bio *bio;
+	int ret = 0;
+	struct swap_info_struct *sis = page_swap_info(page);
+	bool workingset = PageWorkingset(page);
+	unsigned long pflags;
+	bool in_thrashing;
+
+	VM_BUG_ON_PAGE(!PageSwapCache(page) && !synchronous, page);
+	VM_BUG_ON_PAGE(!PageLocked(page), page);
+	VM_BUG_ON_PAGE(PageUptodate(page), page);
+
+	/*
+	 * 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 (frontswap_load(page) == 0) {
+		SetPageUptodate(page);
+		unlock_page(page);
+		goto out;
+	}
+
+	if (data_race(sis->flags & SWP_FS_OPS)) {
+		swap_readpage_fs(page, plug);
+		goto out;
+	}
+
+	if (sis->flags & SWP_SYNCHRONOUS_IO) {
+		ret = bdev_read_page(sis->bdev, swap_page_sector(page), page);
+		if (!ret) {
+			count_vm_event(PSWPIN);
+			goto out;
+		}
+	}
+
+	ret = 0;
+	bio = bio_alloc(sis->bdev, 1, REQ_OP_READ, GFP_KERNEL);
+	bio->bi_iter.bi_sector = swap_page_sector(page);
+	bio->bi_end_io = end_swap_bio_read;
+	bio_add_page(bio, page, thp_size(page), 0);
+	/*
+	 * Keep this task valid during swap readpage because the oom killer may
+	 * attempt to access it in the page fault retry time check.
+	 */
+	if (synchronous) {
+		get_task_struct(current);
+		bio->bi_private = current;
+	}
+	count_vm_event(PSWPIN);
+	bio_get(bio);
+	submit_bio(bio);
+	while (synchronous) {
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (!READ_ONCE(bio->bi_private))
+			break;
+
+		blk_io_schedule();
+	}
+	__set_current_state(TASK_RUNNING);
+	bio_put(bio);
+
+out:
+	if (workingset) {
+		delayacct_thrashing_end(&in_thrashing);
+		psi_memstall_leave(&pflags);
+	}
+	delayacct_swapin_end();
+	return ret;
+}
+
+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);
+}