From: Eric Biggers ebiggers@google.com

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 --- fs/ext4/page-io.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index b66b335a0ca6f..5858fb9b5cd53 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -380,7 +380,8 @@ static int io_submit_init_bio(struct ext4_io_submit *io,

static int 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; @@ -395,10 +396,11 @@ static int io_submit_add_bh(struct ext4_io_submit *io, return ret; io->io_bio->bi_write_hint = inode->i_write_hint; } - 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++; return 0; } @@ -511,7 +513,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io, do { if (!buffer_async_write(bh)) continue; - ret = io_submit_add_bh(io, inode, bounce_page ?: page, bh); + ret = io_submit_add_bh(io, inode, page, bounce_page, bh); if (ret) { /* * We only get here on ENOMEM. Not much else