fixes for handling of split direct I/O bios

[Christoph Hellwig <hch@lst.de>]

Hi all,

this series fixes two problems in the direct I/O code where the
file_offset field in the dio_private structure is used in a context where
we really need the file_offset for the given low-level bios and not for
the bio submitted by the iomap direct I/O as recorded in the dio_private
structure.  To do so we need a new file_offset in the btrfs_dio
structure.

Found by code inspection as part of my bio cleanups.

Diffstat:
 extent_io.c |    1 +
 inode.c     |   18 ++++++++----------
 volumes.h   |    3 +++
 3 files changed, 12 insertions(+), 10 deletions(-)