dm snapshot: separate out exception store interface

Pull structures that bridge the gap between snapshot and
exception store out of dm-snap.h and put them in a new
.h file - dm-exception-store.h.  This file will define the
API for new exception stores.

Ultimately, dm-snap.h is unnecessary, since only dm-snap.c
should be using it.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

4 files changed, 134 insertions, 120 deletions

diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 01590f3e0009..ef152e600cb6 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -7,6 +7,7 @@
  * This file is released under the GPL.
  */
 
+#include "dm-exception-store.h"
 #include "dm-snap.h"
 
 #include <linux/mm.h>
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
new file mode 100644
index 000000000000..d75f775562e5
--- /dev/null
+++ b/drivers/md/dm-exception-store.h
@@ -0,0 +1,131 @@
+/*
+ * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
+ * Copyright (C) 2008 Red Hat, Inc. All rights reserved.
+ *
+ * Device-mapper snapshot exception store.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef _LINUX_DM_EXCEPTION_STORE
+#define _LINUX_DM_EXCEPTION_STORE
+
+#include <linux/blkdev.h>
+
+/*
+ * The snapshot code deals with largish chunks of the disk at a
+ * time. Typically 32k - 512k.
+ */
+typedef sector_t chunk_t;
+
+/*
+ * An exception is used where an old chunk of data has been
+ * replaced by a new one.
+ * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
+ * of chunks that follow contiguously.  Remaining bits hold the number of the
+ * chunk within the device.
+ */
+struct dm_snap_exception {
+        struct list_head hash_list;
+
+        chunk_t old_chunk;
+        chunk_t new_chunk;
+};
+
+/*
+ * Abstraction to handle the meta/layout of exception stores (the
+ * COW device).
+ */
+struct exception_store {
+        /*
+         * Destroys this object when you've finished with it.
+         */
+        void (*destroy) (struct exception_store *store);
+
+        /*
+         * The target shouldn't read the COW device until this is
+         * called.
+         */
+        int (*read_metadata) (struct exception_store *store);
+
+        /*
+         * Find somewhere to store the next exception.
+         */
+        int (*prepare_exception) (struct exception_store *store,
+                                  struct dm_snap_exception *e);
+
+        /*
+         * Update the metadata with this exception.
+         */
+        void (*commit_exception) (struct exception_store *store,
+                                  struct dm_snap_exception *e,
+                                  void (*callback) (void *, int success),
+                                  void *callback_context);
+
+        /*
+         * The snapshot is invalid, note this in the metadata.
+         */
+        void (*drop_snapshot) (struct exception_store *store);
+
+        /*
+         * Return how full the snapshot is.
+         */
+        void (*fraction_full) (struct exception_store *store,
+                               sector_t *numerator,
+                               sector_t *denominator);
+
+        struct dm_snapshot *snap;
+        void *context;
+};
+
+/*
+ * Funtions to manipulate consecutive chunks
+ */
+#  if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
+#    define DM_CHUNK_CONSECUTIVE_BITS 8
+#    define DM_CHUNK_NUMBER_BITS 56
+
+static inline chunk_t dm_chunk_number(chunk_t chunk)
+{
+        return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
+}
+
+static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
+{
+        return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
+}
+
+static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
+{
+        e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
+
+        BUG_ON(!dm_consecutive_chunk_count(e));
+}
+
+#  else
+#    define DM_CHUNK_CONSECUTIVE_BITS 0
+
+static inline chunk_t dm_chunk_number(chunk_t chunk)
+{
+        return chunk;
+}
+
+static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
+{
+        return 0;
+}
+
+static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
+{
+}
+
+#  endif
+
+/*
+ * Two exception store implementations.
+ */
+int dm_create_persistent(struct exception_store *store);
+
+int dm_create_transient(struct exception_store *store);
+
+#endif /* _LINUX_DM_EXCEPTION_STORE */
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index a8005b43a06b..81f03a0e7838 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -21,6 +21,7 @@
 #include <linux/log2.h>
 #include <linux/dm-kcopyd.h>
 
+#include "dm-exception-store.h"
 #include "dm-snap.h"
 #include "dm-bio-list.h"
 
diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
index 99c0106ede2d..6e4beaf89f6c 100644
--- a/drivers/md/dm-snap.h
+++ b/drivers/md/dm-snap.h
@@ -1,6 +1,4 @@
 /*
- * dm-snapshot.c
- *
  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
  *
  * This file is released under the GPL.
@@ -10,6 +8,7 @@
 #define DM_SNAPSHOT_H
 
 #include <linux/device-mapper.h>
+#include "dm-exception-store.h"
 #include "dm-bio-list.h"
 #include <linux/blkdev.h>
 #include <linux/workqueue.h>
@@ -20,116 +19,6 @@ struct exception_table {
         struct list_head *table;
 };
 
-/*
- * The snapshot code deals with largish chunks of the disk at a
- * time. Typically 32k - 512k.
- */
-typedef sector_t chunk_t;
-
-/*
- * An exception is used where an old chunk of data has been
- * replaced by a new one.
- * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number
- * of chunks that follow contiguously.  Remaining bits hold the number of the
- * chunk within the device.
- */
-struct dm_snap_exception {
-        struct list_head hash_list;
-
-        chunk_t old_chunk;
-        chunk_t new_chunk;
-};
-
-/*
- * Funtions to manipulate consecutive chunks
- */
-#  if defined(CONFIG_LBD) || (BITS_PER_LONG == 64)
-#    define DM_CHUNK_CONSECUTIVE_BITS 8
-#    define DM_CHUNK_NUMBER_BITS 56
-
-static inline chunk_t dm_chunk_number(chunk_t chunk)
-{
-        return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL);
-}
-
-static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
-{
-        return e->new_chunk >> DM_CHUNK_NUMBER_BITS;
-}
-
-static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
-{
-        e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS);
-
-        BUG_ON(!dm_consecutive_chunk_count(e));
-}
-
-#  else
-#    define DM_CHUNK_CONSECUTIVE_BITS 0
-
-static inline chunk_t dm_chunk_number(chunk_t chunk)
-{
-        return chunk;
-}
-
-static inline unsigned dm_consecutive_chunk_count(struct dm_snap_exception *e)
-{
-        return 0;
-}
-
-static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)
-{
-}
-
-#  endif
-
-/*
- * Abstraction to handle the meta/layout of exception stores (the
- * COW device).
- */
-struct exception_store {
-
-        /*
-         * Destroys this object when you've finished with it.
-         */
-        void (*destroy) (struct exception_store *store);
-
-        /*
-         * The target shouldn't read the COW device until this is
-         * called.
-         */
-        int (*read_metadata) (struct exception_store *store);
-
-        /*
-         * Find somewhere to store the next exception.
-         */
-        int (*prepare_exception) (struct exception_store *store,
-                                  struct dm_snap_exception *e);
-
-        /*
-         * Update the metadata with this exception.
-         */
-        void (*commit_exception) (struct exception_store *store,
-                                  struct dm_snap_exception *e,
-                                  void (*callback) (void *, int success),
-                                  void *callback_context);
-
-        /*
-         * The snapshot is invalid, note this in the metadata.
-         */
-        void (*drop_snapshot) (struct exception_store *store);
-
-        /*
-         * Return how full the snapshot is.
-         */
-        void (*fraction_full) (struct exception_store *store,
-                               sector_t *numerator,
-                               sector_t *denominator);
-
-        struct dm_snapshot *snap;
-        void *context;
-};
-
 #define DM_TRACKED_CHUNK_HASH_SIZE      16
 #define DM_TRACKED_CHUNK_HASH(x)        ((unsigned long)(x) & \
                                          (DM_TRACKED_CHUNK_HASH_SIZE - 1))
@@ -193,14 +82,6 @@ struct dm_snapshot {
 int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
 
 /*
- * Constructor and destructor for the default persistent
- * store.
- */
-int dm_create_persistent(struct exception_store *store);
-
-int dm_create_transient(struct exception_store *store);
-
-/*
  * Return the number of sectors in the device.
  */
 static inline sector_t get_dev_size(struct block_device *bdev)