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>

1 files changed, 17 insertions, 4 deletions

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?