dm: teach dm-targets to use a dax_device + dax_operations

Arrange for dm to lookup the dax services available from member devices.
Update the dax-capable targets, linear and stripe, to route dax
operations to the underlying device. Changes the target-internal
->direct_access() method to more closely align with the dax_operations
->direct_access() calling convention.

Cc: Toshi Kani <toshi.kani@hpe.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 6 insertions, 10 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index bd56dfe43a99..ef4c6f8cad47 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -630,6 +630,7 @@ static int open_table_device(struct table_device *td, dev_t dev,
 	}
 
 	td->dm_dev.bdev = bdev;
+	td->dm_dev.dax_dev = dax_get_by_host(bdev->bd_disk->disk_name);
 	return 0;
 }
 
@@ -643,7 +644,9 @@ static void close_table_device(struct table_device *td, struct mapped_device *md
 
 	bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md));
 	blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
+	put_dax(td->dm_dev.dax_dev);
 	td->dm_dev.bdev = NULL;
+	td->dm_dev.dax_dev = NULL;
 }
 
 static struct table_device *find_table_device(struct list_head *l, dev_t dev,
@@ -945,16 +948,9 @@ static long dm_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
 	if (len < 1)
 		goto out;
 	nr_pages = min(len, nr_pages);
-	if (ti->type->direct_access) {
-		ret = ti->type->direct_access(ti, sector, kaddr, pfn,
-				nr_pages * PAGE_SIZE);
-		/*
-		 * FIXME: convert ti->type->direct_access to return
-		 * nr_pages directly.
-		 */
-		if (ret >= 0)
-			ret /= PAGE_SIZE;
-	}
+	if (ti->type->direct_access)
+		ret = ti->type->direct_access(ti, pgoff, nr_pages, kaddr, pfn);
+
  out:
 	dm_put_live_table(md, srcu_idx);