From: Eric Biggers <ebiggers@google.com>

Date: Thu, 2 Feb 2023 16:55:03 -0800

Subject: [PATCH] ext4: fix cgroup writeback accounting with fs-layer

 encryption

References: bsc#1012628

Patch-mainline: 6.2.7

Git-commit: ffec85d53d0f39ee4680a2cf0795255e000e1feb

commit ffec85d53d0f39ee4680a2cf0795255e000e1feb upstream.

When writing a page from an encrypted file that is using

filesystem-layer encryption (not inline encryption), ext4 encrypts the

pagecache page into a bounce page, then writes the bounce page.

It also passes the bounce page to wbc_account_cgroup_owner().  That's

incorrect, because the bounce page is a newly allocated temporary page

that doesn't have the memory cgroup of the original pagecache page.

This makes wbc_account_cgroup_owner() not account the I/O to the owner

of the pagecache page as it should.

Fix this by always passing the pagecache page to

wbc_account_cgroup_owner().

Fixes: 001e4a8775f6 ("ext4: implement cgroup writeback support")

Cc: stable@vger.kernel.org

Reported-by: Matthew Wilcox (Oracle) <willy@infradead.org>

Signed-off-by: Eric Biggers <ebiggers@google.com>

Acked-by: Tejun Heo <tj@kernel.org>

Link: https://lore.kernel.org/r/20230203005503.141557-1-ebiggers@kernel.org

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

---

 fs/ext4/page-io.c | 11 ++++++-----

 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c

index beaec6d8..1e4db96a 100644

--- a/fs/ext4/page-io.c

+++ b/fs/ext4/page-io.c

@@ -409,7 +409,8 @@ static void io_submit_init_bio(struct ext4_io_submit *io,

 static void io_submit_add_bh(struct ext4_io_submit *io,

 			     struct inode *inode,

-			     struct page *page,

+			     struct page *pagecache_page,

+			     struct page *bounce_page,

 			     struct buffer_head *bh)

 {

 	int ret;

@@ -421,10 +422,11 @@ static void io_submit_add_bh(struct ext4_io_submit *io,

 	}

 	if (io->io_bio == NULL)

 		io_submit_init_bio(io, bh);

-	ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh));

+	ret = bio_add_page(io->io_bio, bounce_page ?: pagecache_page,

+			   bh->b_size, bh_offset(bh));

 	if (ret != bh->b_size)

 		goto submit_and_retry;

-	wbc_account_cgroup_owner(io->io_wbc, page, bh->b_size);

+	wbc_account_cgroup_owner(io->io_wbc, pagecache_page, bh->b_size);

 	io->io_next_block++;

 }

@@ -561,8 +563,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,

 	do {

 		if (!buffer_async_write(bh))

 			continue;

-		io_submit_add_bh(io, inode,

-				 bounce_page ? bounce_page : page, bh);

+		io_submit_add_bh(io, inode, page, bounce_page, bh);

 	} while ((bh = bh->b_this_page) != head);

 unlock:

 	unlock_page(page);

-- 

2.35.3