dm cache: add policy name to status output
The cache's policy may have been established using the "default" alias,
which is currently the "mq" policy but the default policy may change in
the future. It is useful to know exactly which policy is being used.
Add a 'real' member to the dm_cache_policy_type structure and have the
"default" dm_cache_policy_type point to the real "mq"
dm_cache_policy_type. Update dm_cache_policy_get_name() to check if
real is set, if so report the name of the real policy (not the alias).
Requested-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
index e63e36c..930e8c3 100644
--- a/drivers/md/dm-cache-policy-mq.c
+++ b/drivers/md/dm-cache-policy-mq.c
@@ -1276,7 +1276,8 @@
.version = {1, 2, 0},
.hint_size = 4,
.owner = THIS_MODULE,
- .create = mq_create
+ .create = mq_create,
+ .real = &mq_policy_type
};
static int __init mq_init(void)
diff --git a/drivers/md/dm-cache-policy.c b/drivers/md/dm-cache-policy.c
index d800579..c1a3cee 100644
--- a/drivers/md/dm-cache-policy.c
+++ b/drivers/md/dm-cache-policy.c
@@ -146,6 +146,10 @@
{
struct dm_cache_policy_type *t = p->private;
+ /* if t->real is set then an alias was used (e.g. "default") */
+ if (t->real)
+ return t->real->name;
+
return t->name;
}
EXPORT_SYMBOL_GPL(dm_cache_policy_get_name);
diff --git a/drivers/md/dm-cache-policy.h b/drivers/md/dm-cache-policy.h
index 052c00a..f50fe36 100644
--- a/drivers/md/dm-cache-policy.h
+++ b/drivers/md/dm-cache-policy.h
@@ -223,6 +223,12 @@
unsigned version[CACHE_POLICY_VERSION_SIZE];
/*
+ * For use by an alias dm_cache_policy_type to point to the
+ * real dm_cache_policy_type.
+ */
+ struct dm_cache_policy_type *real;
+
+ /*
* Policies may store a hint for each each cache block.
* Currently the size of this hint must be 0 or 4 bytes but we
* expect to relax this in future.
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index 11ad705..09334c2 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -2832,7 +2832,7 @@
* <#demotions> <#promotions> <#dirty>
* <#features> <features>*
* <#core args> <core args>
- * <#policy args> <policy args>*
+ * <policy name> <#policy args> <policy args>*
*/
static void cache_status(struct dm_target *ti, status_type_t type,
unsigned status_flags, char *result, unsigned maxlen)
@@ -2900,6 +2900,8 @@
}
DMEMIT("2 migration_threshold %llu ", (unsigned long long) cache->migration_threshold);
+
+ DMEMIT("%s ", dm_cache_policy_get_name(cache->policy));
if (sz < maxlen) {
r = policy_emit_config_values(cache->policy, result + sz, maxlen - sz);
if (r)