If a page is already locked, attempting to dirty it leads to a deadlock
in lock_page(). This is what currently happens to ITER_BVEC pages when
a dio-enabled loop device is backed by ceph:
$ losetup --direct-io /dev/loop0 /mnt/cephfs/img
$ xfs_io -c 'pread 0 4k' /dev/loop0
Follow other file systems and only dirty ITER_IOVEC pages.
Cc: stable@kernel.org
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
