This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / drivers / md / dm-snap.h

diff --git a/drivers/md/dm-snap.h b/drivers/md/dm-snap.h
new file mode 100644 (file)
index 0000000..375aa24
--- /dev/null
+++ b/drivers/md/dm-snap.h
@@ -0,0 +1,161 @@
+/*
+ * dm-snapshot.c
+ *
+ * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_SNAPSHOT_H
+#define DM_SNAPSHOT_H
+
+#include "dm.h"
+#include <linux/blkdev.h>
+
+struct exception_table {
+       uint32_t hash_mask;
+       struct list_head *table;
+};
+
+/*
+ * The snapshot code deals with largish chunks of the disk at a
+ * time. Typically 64k - 256k.
+ */
+/* FIXME: can we get away with limiting these to a uint32_t ? */
+typedef sector_t chunk_t;
+
+/*
+ * An exception is used where an old chunk of data has been
+ * replaced by a new one.
+ */
+struct 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 exception *e);
+
+       /*
+        * Update the metadata with this exception.
+        */
+       void (*commit_exception) (struct exception_store *store,
+                                 struct 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;
+};
+
+struct dm_snapshot {
+       struct rw_semaphore lock;
+       struct dm_table *table;
+
+       struct dm_dev *origin;
+       struct dm_dev *cow;
+
+       /* List of snapshots per Origin */
+       struct list_head list;
+
+       /* Size of data blocks saved - must be a power of 2 */
+       chunk_t chunk_size;
+       chunk_t chunk_mask;
+       chunk_t chunk_shift;
+
+       /* You can't use a snapshot if this is 0 (e.g. if full) */
+       int valid;
+       int have_metadata;
+
+       /* Used for display of table */
+       char type;
+
+       /* The last percentage we notified */
+       int last_percent;
+
+       struct exception_table pending;
+       struct exception_table complete;
+
+       /* The on disk metadata handler */
+       struct exception_store store;
+
+       struct kcopyd_client *kcopyd_client;
+};
+
+/*
+ * Used by the exception stores to load exceptions hen
+ * initialising.
+ */
+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, uint32_t chunk_size);
+
+int dm_create_transient(struct exception_store *store,
+                       struct dm_snapshot *s, int blocksize);
+
+/*
+ * Return the number of sectors in the device.
+ */
+static inline sector_t get_dev_size(struct block_device *bdev)
+{
+       return bdev->bd_inode->i_size >> SECTOR_SHIFT;
+}
+
+static inline chunk_t sector_to_chunk(struct dm_snapshot *s, sector_t sector)
+{
+       return (sector & ~s->chunk_mask) >> s->chunk_shift;
+}
+
+static inline sector_t chunk_to_sector(struct dm_snapshot *s, chunk_t chunk)
+{
+       return chunk << s->chunk_shift;
+}
+
+static inline int bdev_equal(struct block_device *lhs, struct block_device *rhs)
+{
+       /*
+        * There is only ever one instance of a particular block
+        * device so we can compare pointers safely.
+        */
+       return lhs == rhs;
+}
+
+#endif