dax-capable mapped-device is marked as DM_TYPE_DAX_BIO_BASED,
which supports both dax and bio-based operations. dm-snap
needs to work with dax-capable device when bio-based operation
is used.
Add fake origin_direct_access() to origin device so that its
origin device is also marked as DM_TYPE_DAX_BIO_BASED for
dax-capable device. This allows to extend target's DM table.
dm-snap works normally when bio-based operation is used.
dm-snap does not support dax operation, and mount with dax
option to a target device or snapshot device fails.
Signed-off-by: Toshi Kani <toshi.k...@hpe.com>
Cc: Mike Snitzer <snit...@redhat.com>
Cc: Alasdair Kergon <a...@redhat.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
---
drivers/md/dm-snap.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 69ab1ff..c472f04 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -2301,6 +2301,13 @@ static int origin_map(struct dm_target *ti, struct bio
*bio)
return do_origin(o->dev, bio);
}
+static long origin_direct_access(struct dm_target *ti, sector_t sector,
+ void __pmem **kaddr, pfn_t *pfn, long size)
+{
+ DMWARN("device does not support dax.");
+ return -EIO;
+}
+
/*
* Set the target "max_io_len" field to the minimum of all the snapshots'
* chunk sizes.
@@ -2360,6 +2367,7 @@ static struct target_type origin_target = {
.postsuspend = origin_postsuspend,
.status = origin_status,
.iterate_devices = origin_iterate_devices,
+ .direct_access = origin_direct_access,
};
static struct target_type snapshot_target = {
