dm cache: add remove_cblock method to policy interface

Implement policy_remove_cblock() and add remove_cblock method to the mq
policy.  These methods will be used by the following cache block
invalidation patch which adds the 'invalidate_cblocks' message to the
cache core.

Also, update some comments in dm-cache-policy.h

Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

3 files changed, 57 insertions, 4 deletions

diff --git a/drivers/md/dm-cache-policy-internal.h b/drivers/md/dm-cache-policy-internal.h
index a75f7e7498eb..2256a1f24f73 100644
--- a/drivers/md/dm-cache-policy-internal.h
+++ b/drivers/md/dm-cache-policy-internal.h
@@ -64,6 +64,11 @@ static inline void policy_remove_mapping(struct dm_cache_policy *p, dm_oblock_t
         p->remove_mapping(p, oblock);
 }
 
+static inline int policy_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock)
+{
+        return p->remove_cblock(p, cblock);
+}
+
 static inline void policy_force_mapping(struct dm_cache_policy *p,
                                         dm_oblock_t current_oblock, dm_oblock_t new_oblock)
 {
diff --git a/drivers/md/dm-cache-policy-mq.c b/drivers/md/dm-cache-policy-mq.c
index 782bf854666a..7209fab8b8ed 100644
--- a/drivers/md/dm-cache-policy-mq.c
+++ b/drivers/md/dm-cache-policy-mq.c
@@ -304,6 +304,15 @@ static void free_entry(struct entry_pool *ep, struct entry *e)
         list_add(&e->list, &ep->free);
 }
 
+/*
+ * Returns NULL if the entry is free.
+ */
+static struct entry *epool_find(struct entry_pool *ep, dm_cblock_t cblock)
+{
+        struct entry *e = ep->entries + from_cblock(cblock);
+        return e->hlist.pprev ? e : NULL;
+}
+
 static bool epool_empty(struct entry_pool *ep)
 {
         return list_empty(&ep->free);
@@ -1020,6 +1029,31 @@ static void mq_remove_mapping(struct dm_cache_policy *p, dm_oblock_t oblock)
         mutex_unlock(&mq->lock);
 }
 
+static int __remove_cblock(struct mq_policy *mq, dm_cblock_t cblock)
+{
+        struct entry *e = epool_find(&mq->cache_pool, cblock);
+
+        if (!e)
+                return -ENODATA;
+
+        del(mq, e);
+        free_entry(&mq->cache_pool, e);
+
+        return 0;
+}
+
+static int mq_remove_cblock(struct dm_cache_policy *p, dm_cblock_t cblock)
+{
+        int r;
+        struct mq_policy *mq = to_mq_policy(p);
+
+        mutex_lock(&mq->lock);
+        r = __remove_cblock(mq, cblock);
+        mutex_unlock(&mq->lock);
+
+        return r;
+}
+
 static int __mq_writeback_work(struct mq_policy *mq, dm_oblock_t *oblock,
                               dm_cblock_t *cblock)
 {
@@ -1139,6 +1173,7 @@ static void init_policy_functions(struct mq_policy *mq)
         mq->policy.load_mapping = mq_load_mapping;
         mq->policy.walk_mappings = mq_walk_mappings;
         mq->policy.remove_mapping = mq_remove_mapping;
+        mq->policy.remove_cblock = mq_remove_cblock;
         mq->policy.writeback_work = mq_writeback_work;
         mq->policy.force_mapping = mq_force_mapping;
         mq->policy.residency = mq_residency;
diff --git a/drivers/md/dm-cache-policy.h b/drivers/md/dm-cache-policy.h
index 33369ca9614f..052c00a84a5c 100644
--- a/drivers/md/dm-cache-policy.h
+++ b/drivers/md/dm-cache-policy.h
@@ -135,9 +135,6 @@ struct dm_cache_policy {
          */
         int (*lookup)(struct dm_cache_policy *p, dm_oblock_t oblock, dm_cblock_t *cblock);
 
-        /*
-         * oblock must be a mapped block.  Must not block.
-         */
         void (*set_dirty)(struct dm_cache_policy *p, dm_oblock_t oblock);
         void (*clear_dirty)(struct dm_cache_policy *p, dm_oblock_t oblock);
 
@@ -159,8 +156,24 @@ struct dm_cache_policy {
         void (*force_mapping)(struct dm_cache_policy *p, dm_oblock_t current_oblock,
                               dm_oblock_t new_oblock);
 
-        int (*writeback_work)(struct dm_cache_policy *p, dm_oblock_t *oblock, dm_cblock_t *cblock);
+        /*
+         * This is called via the invalidate_cblocks message.  It is
+         * possible the particular cblock has already been removed due to a
+         * write io in passthrough mode.  In which case this should return
+         * -ENODATA.
+         */
+        int (*remove_cblock)(struct dm_cache_policy *p, dm_cblock_t cblock);
 
+        /*
+         * Provide a dirty block to be written back by the core target.
+         *
+         * Returns:
+         *
+         * 0 and @cblock,@oblock: block to write back provided
+         *
+         * -ENODATA: no dirty blocks available
+         */
+        int (*writeback_work)(struct dm_cache_policy *p, dm_oblock_t *oblock, dm_cblock_t *cblock);
 
         /*
          * How full is the cache?