Merge tag 'dm-3.9-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm

Pull device-mapper update from Alasdair G Kergon:
 "The main addition here is a long-desired target framework to allow an
  SSD to be used as a cache in front of a slower device.  Cache tuning
  is delegated to interchangeable policy modules so these can be
  developed independently of the mechanics needed to shuffle the data
  around.

  Other than that, kcopyd users acquire a throttling parameter, ioctl
  buffer usage gets streamlined, more mempool reliance is reduced and
  there are a few other bug fixes and tidy-ups."

* tag 'dm-3.9-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm: (30 commits)
  dm cache: add cleaner policy
  dm cache: add mq policy
  dm: add cache target
  dm persistent data: add bitset
  dm persistent data: add transactional array
  dm thin: remove cells from stack
  dm bio prison: pass cell memory in
  dm persistent data: add btree_walk
  dm: add target num_write_bios fn
  dm kcopyd: introduce configurable throttling
  dm ioctl: allow message to return data
  dm ioctl: optimize functions without variable params
  dm ioctl: introduce ioctl_flags
  dm: merge io_pool and tio_pool
  dm: remove unused _rq_bio_info_cache
  dm: fix limits initialization when there are no data devices
  dm snapshot: add missing module aliases
  dm persistent data: set some btree fn parms const
  dm: refactor bio cloning
  dm: rename bio cloning functions
  ...

1 files changed, 49 insertions, 9 deletions

diff --git a/drivers/md/dm-bio-prison.h b/drivers/md/dm-bio-prison.h
index 53d1a7a84e2..3f833190ead 100644
--- a/drivers/md/dm-bio-prison.h
+++ b/drivers/md/dm-bio-prison.h
@@ -22,7 +22,6 @@
  * subsequently unlocked the bios become available.
  */
 struct dm_bio_prison;
-struct dm_bio_prison_cell;
 
 /* FIXME: this needs to be more abstract */
 struct dm_cell_key {
@@ -31,21 +30,62 @@ struct dm_cell_key {
 	dm_block_t block;
 };
 
+/*
+ * Treat this as opaque, only in header so callers can manage allocation
+ * themselves.
+ */
+struct dm_bio_prison_cell {
+	struct hlist_node list;
+	struct dm_cell_key key;
+	struct bio *holder;
+	struct bio_list bios;
+};
+
 struct dm_bio_prison *dm_bio_prison_create(unsigned nr_cells);
 void dm_bio_prison_destroy(struct dm_bio_prison *prison);
 
 /*
- * This may block if a new cell needs allocating.  You must ensure that
- * cells will be unlocked even if the calling thread is blocked.
+ * These two functions just wrap a mempool.  This is a transitory step:
+ * Eventually all bio prison clients should manage their own cell memory.
  *
- * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ * Like mempool_alloc(), dm_bio_prison_alloc_cell() can only fail if called
+ * in interrupt context or passed GFP_NOWAIT.
  */
-int dm_bio_detain(struct dm_bio_prison *prison, struct dm_cell_key *key,
-		  struct bio *inmate, struct dm_bio_prison_cell **ref);
+struct dm_bio_prison_cell *dm_bio_prison_alloc_cell(struct dm_bio_prison *prison,
+						    gfp_t gfp);
+void dm_bio_prison_free_cell(struct dm_bio_prison *prison,
+			     struct dm_bio_prison_cell *cell);
 
-void dm_cell_release(struct dm_bio_prison_cell *cell, struct bio_list *bios);
-void dm_cell_release_no_holder(struct dm_bio_prison_cell *cell, struct bio_list *inmates);
-void dm_cell_error(struct dm_bio_prison_cell *cell);
+/*
+ * Creates, or retrieves a cell for the given key.
+ *
+ * Returns 1 if pre-existing cell returned, zero if new cell created using
+ * @cell_prealloc.
+ */
+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);
+
+/*
+ * An atomic op that combines retrieving a cell, and adding a bio to it.
+ *
+ * Returns 1 if the cell was already held, 0 if @inmate is the new holder.
+ */
+int dm_bio_detain(struct dm_bio_prison *prison,
+		  struct dm_cell_key *key,
+		  struct bio *inmate,
+		  struct dm_bio_prison_cell *cell_prealloc,
+		  struct dm_bio_prison_cell **cell_result);
+
+void dm_cell_release(struct dm_bio_prison *prison,
+		     struct dm_bio_prison_cell *cell,
+		     struct bio_list *bios);
+void dm_cell_release_no_holder(struct dm_bio_prison *prison,
+			       struct dm_bio_prison_cell *cell,
+			       struct bio_list *inmates);
+void dm_cell_error(struct dm_bio_prison *prison,
+		   struct dm_bio_prison_cell *cell);
 
 /*----------------------------------------------------------------*/