ext2, ext4, xfs: retrieve dax_device for iomap operations

In preparation for converting fs/dax.c to use dax_direct_access()
instead of bdev_direct_access(), add the plumbing to retrieve the
dax_device associated with a given block_device.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 7291810067eb..f753e788da31 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -41,6 +41,7 @@ struct iomap {
         u16                     type;   /* type of mapping */
         u16                     flags;  /* flags for mapping */
         struct block_device     *bdev;  /* block device for I/O */
+        struct dax_device       *dax_dev; /* dax_dev for dax operations */
 };
 
 /*