dm: add cache target
Add a target that allows a fast device such as an SSD to be used as a
cache for a slower device such as a disk.
A plug-in architecture was chosen so that the decisions about which data
to migrate and when are delegated to interchangeable tunable policy
modules. The first general purpose module we have developed, called
"mq" (multiqueue), follows in the next patch. Other modules are
under development.
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/drivers/md/dm-bio-prison.c b/drivers/md/dm-bio-prison.c
index 144067c..85f0b70 100644
--- a/drivers/md/dm-bio-prison.c
+++ b/drivers/md/dm-bio-prison.c
@@ -179,6 +179,15 @@
}
EXPORT_SYMBOL_GPL(dm_bio_detain);
+int dm_get_cell(struct dm_bio_prison *prison,
+ struct dm_cell_key *key,
+ struct dm_bio_prison_cell *cell_prealloc,
+ struct dm_bio_prison_cell **cell_result)
+{
+ return bio_detain(prison, key, NULL, cell_prealloc, cell_result);
+}
+EXPORT_SYMBOL_GPL(dm_get_cell);
+
/*
* @inmates must have been initialised prior to this call
*/