Commit ffec85d5 authored by Eric Biggers's avatar Eric Biggers Committed by Theodore Ts'o
Browse files

ext4: fix cgroup writeback accounting with fs-layer encryption 



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: 001e4a87 ("ext4: implement cgroup writeback support")
Cc: stable@vger.kernel.org
Reported-by: default avatarMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230203005503.141557-1-ebiggers@kernel.org


Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent e3645d72

fs/ext4/page-io.c

+6 −5
Original line number Original line Diff line number Diff line
@@ -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,

static void io_submit_add_bh(struct ext4_io_submit *io,

			     struct inode *inode,

			     struct inode *inode,

			     struct page *page,

			     struct page *pagecache_page,

			     struct page *bounce_page,

			     struct buffer_head *bh)

			     struct buffer_head *bh)

{

{

	int ret;

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

	}

	if (io->io_bio == NULL)

	if (io->io_bio == NULL)

		io_submit_init_bio(io, bh);

		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)

	if (ret != bh->b_size)

		goto submit_and_retry;

		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++;

	io->io_next_block++;

}

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

	do {

		if (!buffer_async_write(bh))

		if (!buffer_async_write(bh))

			continue;

			continue;

		io_submit_add_bh(io, inode,

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

				 bounce_page ? bounce_page : page, bh);

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

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

unlock:

unlock:

	unlock_page(page);

	unlock_page(page);