dm snapshot: extend exception store functions

Supply dm_add_exception as a callback to the read_metadata function.
Add a status function ready for a later patch and name the functions
consistently.

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

6 files changed, 55 insertions, 37 deletions

diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 74777e0f80df..dccbfb0e010f 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -11,7 +11,6 @@
 #include <linux/pagemap.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>
-#include <linux/device-mapper.h>
 
 #define DM_MSG_PREFIX "snapshot exception stores"
 
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
index 78d1acec77e9..bb9f33d5daa2 100644
--- a/drivers/md/dm-exception-store.h
+++ b/drivers/md/dm-exception-store.h
@@ -11,6 +11,7 @@
 #define _LINUX_DM_EXCEPTION_STORE
 
 #include <linux/blkdev.h>
+#include <linux/device-mapper.h>
 
 /*
  * The snapshot code deals with largish chunks of the disk at a
@@ -37,7 +38,6 @@ struct dm_snap_exception {
  * COW device).
  */
 struct dm_exception_store {
-
         /*
          * Destroys this object when you've finished with it.
          */
@@ -45,9 +45,13 @@ struct dm_exception_store {
 
         /*
          * The target shouldn't read the COW device until this is
-         * called.
+         * called.  As exceptions are read from the COW, they are
+         * reported back via the callback.
          */
-        int (*read_metadata) (struct dm_exception_store *store);
+        int (*read_metadata) (struct dm_exception_store *store,
+                              int (*callback)(void *callback_context,
+                                              chunk_t old, chunk_t new),
+                              void *callback_context);
 
         /*
          * Find somewhere to store the next exception.
@@ -68,6 +72,9 @@ struct dm_exception_store {
          */
         void (*drop_snapshot) (struct dm_exception_store *store);
 
+        int (*status) (struct dm_exception_store *store, status_type_t status,
+                       char *result, unsigned int maxlen);
+
         /*
          * Return how full the snapshot is.
          */
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index 57c946c69ee7..936b34e0959f 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -395,7 +395,11 @@ static void write_exception(struct pstore *ps,
  * 'full' is filled in to indicate if the area has been
  * filled.
  */
-static int insert_exceptions(struct pstore *ps, int *full)
+static int insert_exceptions(struct pstore *ps,
+                             int (*callback)(void *callback_context,
+                                             chunk_t old, chunk_t new),
+                             void *callback_context,
+                             int *full)
 {
         int r;
         unsigned int i;
@@ -428,7 +432,7 @@ static int insert_exceptions(struct pstore *ps, int *full)
                 /*
                  * Otherwise we add the exception to the snapshot.
                  */
-                r = dm_add_exception(ps->snap, de.old_chunk, de.new_chunk);
+                r = callback(callback_context, de.old_chunk, de.new_chunk);
                 if (r)
                         return r;
         }
@@ -436,7 +440,10 @@ static int insert_exceptions(struct pstore *ps, int *full)
         return 0;
 }
 
-static int read_exceptions(struct pstore *ps)
+static int read_exceptions(struct pstore *ps,
+                           int (*callback)(void *callback_context, chunk_t old,
+                                           chunk_t new),
+                           void *callback_context)
 {
         int r, full = 1;
 
@@ -449,7 +456,7 @@ static int read_exceptions(struct pstore *ps)
                 if (r)
                         return r;
 
-                r = insert_exceptions(ps, &full);
+                r = insert_exceptions(ps, callback, callback_context, &full);
                 if (r)
                         return r;
         }
@@ -482,7 +489,10 @@ static void persistent_destroy(struct dm_exception_store *store)
         kfree(ps);
 }
 
-static int persistent_read_metadata(struct dm_exception_store *store)
+static int persistent_read_metadata(struct dm_exception_store *store,
+                                    int (*callback)(void *callback_context,
+                                                    chunk_t old, chunk_t new),
+                                    void *callback_context)
 {
         int r, uninitialized_var(new_snapshot);
         struct pstore *ps = get_info(store);
@@ -540,7 +550,7 @@ static int persistent_read_metadata(struct dm_exception_store *store)
                 /*
                  * Read the metadata.
                  */
-                r = read_exceptions(ps);
+                r = read_exceptions(ps, callback, callback_context);
                 if (r)
                         return r;
         }
@@ -548,8 +558,8 @@ static int persistent_read_metadata(struct dm_exception_store *store)
         return 0;
 }
 
-static int persistent_prepare(struct dm_exception_store *store,
-                              struct dm_snap_exception *e)
+static int persistent_prepare_exception(struct dm_exception_store *store,
+                                        struct dm_snap_exception *e)
 {
         struct pstore *ps = get_info(store);
         uint32_t stride;
@@ -575,10 +585,10 @@ static int persistent_prepare(struct dm_exception_store *store,
         return 0;
 }
 
-static void persistent_commit(struct dm_exception_store *store,
-                              struct dm_snap_exception *e,
-                              void (*callback) (void *, int success),
-                              void *callback_context)
+static void persistent_commit_exception(struct dm_exception_store *store,
+                                        struct dm_snap_exception *e,
+                                        void (*callback) (void *, int success),
+                                        void *callback_context)
 {
         unsigned int i;
         struct pstore *ps = get_info(store);
@@ -637,7 +647,7 @@ static void persistent_commit(struct dm_exception_store *store,
         ps->callback_count = 0;
 }
 
-static void persistent_drop(struct dm_exception_store *store)
+static void persistent_drop_snapshot(struct dm_exception_store *store)
 {
         struct pstore *ps = get_info(store);
 
@@ -675,9 +685,9 @@ int dm_create_persistent(struct dm_exception_store *store)
 
         store->destroy = persistent_destroy;
         store->read_metadata = persistent_read_metadata;
-        store->prepare_exception = persistent_prepare;
-        store->commit_exception = persistent_commit;
-        store->drop_snapshot = persistent_drop;
+        store->prepare_exception = persistent_prepare_exception;
+        store->commit_exception = persistent_commit_exception;
+        store->drop_snapshot = persistent_drop_snapshot;
         store->fraction_full = persistent_fraction_full;
         store->context = ps;
 
diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
index 2a781df57fef..7f6e2e6dcb0d 100644
--- a/drivers/md/dm-snap-transient.c
+++ b/drivers/md/dm-snap-transient.c
@@ -28,13 +28,16 @@ static void transient_destroy(struct dm_exception_store *store)
         kfree(store->context);
 }
 
-static int transient_read_metadata(struct dm_exception_store *store)
+static int transient_read_metadata(struct dm_exception_store *store,
+                                   int (*callback)(void *callback_context,
+                                                   chunk_t old, chunk_t new),
+                                   void *callback_context)
 {
         return 0;
 }
 
-static int transient_prepare(struct dm_exception_store *store,
-                             struct dm_snap_exception *e)
+static int transient_prepare_exception(struct dm_exception_store *store,
+                                       struct dm_snap_exception *e)
 {
         struct transient_c *tc = (struct transient_c *) store->context;
         sector_t size = get_dev_size(store->snap->cow->bdev);
@@ -48,10 +51,10 @@ static int transient_prepare(struct dm_exception_store *store,
         return 0;
 }
 
-static void transient_commit(struct dm_exception_store *store,
-                             struct dm_snap_exception *e,
-                             void (*callback) (void *, int success),
-                             void *callback_context)
+static void transient_commit_exception(struct dm_exception_store *store,
+                                       struct dm_snap_exception *e,
+                                       void (*callback) (void *, int success),
+                                       void *callback_context)
 {
         /* Just succeed */
         callback(callback_context, 1);
@@ -70,8 +73,8 @@ int dm_create_transient(struct dm_exception_store *store)
 
         store->destroy = transient_destroy;
         store->read_metadata = transient_read_metadata;
-        store->prepare_exception = transient_prepare;
-        store->commit_exception = transient_commit;
+        store->prepare_exception = transient_prepare_exception;
+        store->commit_exception = transient_commit_exception;
         store->drop_snapshot = NULL;
         store->fraction_full = transient_fraction_full;
 
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 018b567fc758..65ff82ff124e 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -430,8 +430,13 @@ out:
         list_add(&new_e->hash_list, e ? &e->hash_list : l);
 }
 
-int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new)
+/*
+ * Callback used by the exception stores to load exceptions when
+ * initialising.
+ */
+static int dm_add_exception(void *context, chunk_t old, chunk_t new)
 {
+        struct dm_snapshot *s = context;
         struct dm_snap_exception *e;
 
         e = alloc_exception();
@@ -660,7 +665,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
         spin_lock_init(&s->tracked_chunk_lock);
 
         /* Metadata must only be loaded into one table at once */
-        r = s->store.read_metadata(&s->store);
+        r = s->store.read_metadata(&s->store, dm_add_exception, (void *)s);
         if (r < 0) {
                 ti->error = "Failed to read snapshot metadata";
                 goto bad_load_and_register;
diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
index 928123657024..d9e62b43cf85 100644
--- a/drivers/md/dm-snap.h
+++ b/drivers/md/dm-snap.h
@@ -76,12 +76,6 @@ struct dm_snapshot {
 };
 
 /*
- * Used by the exception stores to load exceptions hen
- * initialising.
- */
-int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
-
-/*
  * Return the number of sectors in the device.
  */
 static inline sector_t get_dev_size(struct block_device *bdev)