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Commit 4008fb9a authored by Eric Biggers's avatar Eric Biggers Committed by Greg Kroah-Hartman
Browse files

ext4: fix cgroup writeback accounting with fs-layer encryption 



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: 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>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent e4b5c766

fs/ext4/page-io.c

+6 −4
Original line number Diff line number Diff line
@@ -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