Unverified Commit 9fa7384d authored by openeuler-ci-bot's avatar openeuler-ci-bot Committed by Gitee
Browse files

!15486 mm: fix unexpected zeroed page mapping with zram swap 

Merge Pull Request from: @ci-robot 
 
PR sync from: Liu Shixin <liushixin2@huawei.com>
https://mailweb.openeuler.org/archives/list/kernel@openeuler.org/message/IUCJWXKPKWSAIKNIFRQVXK4XADJ2KBU6/ 
 
https://gitee.com/src-openeuler/kernel/issues/IBP28G 
 
Link:https://gitee.com/openeuler/kernel/pulls/15486

 

Reviewed-by: default avatarYuan Can <yuancan@huawei.com>
Signed-off-by: default avatarYuan Can <yuancan@huawei.com>
parents 3be46f29 aa41f26d

mm/page_io.c

+0 −55
Original line number Diff line number Diff line
@@ -71,55 +71,6 @@ void end_swap_bio_write(struct bio *bio) 
	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);
@@ -135,7 +86,6 @@ static void end_swap_bio_read(struct bio *bio) 
	}



	SetPageUptodate(page);

	swap_slot_free_notify(page);

out:

	unlock_page(page);

	WRITE_ONCE(bio->bi_private, NULL);
@@ -373,11 +323,6 @@ int swap_readpage(struct page *page, bool synchronous) 


	ret = bdev_read_page(sis->bdev, map_swap_page(page, &sis->bdev), page);

	if (!ret) {

		if (trylock_page(page)) {

			swap_slot_free_notify(page);

			unlock_page(page);

		}



		count_vm_event(PSWPIN);

		return 0;

	}