From: Eric Biggers ebiggers@google.com

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 --- 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 beaec6d81074a..1e4db96a04e63 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);

base-commit: 6d796c50f84ca79f1722bb131799e5a5710c4700