Merge git://git.kernel.org/pub/scm/linux/kernel/git/steve/linux-dm

* git://git.kernel.org/pub/scm/linux/kernel/git/steve/linux-dm:
  dm: raid fix device status indicator when array initializing
  dm log userspace: add log device dependency
  dm log userspace: fix comment hyphens
  dm: add thin provisioning target
  dm: add persistent data library
  dm: add bufio
  dm: export dm get md
  dm table: add immutable feature
  dm table: add always writeable feature
  dm table: add singleton feature
  dm kcopyd: add dm_kcopyd_zero to zero an area
  dm: remove superfluous smp_mb
  dm: use local printk ratelimit
  dm table: propagate non rotational flag

Documentation/device-mapper/dm-log.txt

@@ -48,7 +48,7 @@ kernel and userspace, 'connector' is used as the interface for
 communication.
 
 There are currently two userspace log implementations that leverage this
-framework - "clustered_disk" and "clustered_core".  These implementations
+framework - "clustered-disk" and "clustered-core".  These implementations
 provide a cluster-coherent log for shared-storage.  Device-mapper mirroring
 can be used in a shared-storage environment when the cluster log implementations
 are employed.

Documentation/device-mapper/persistent-data.txt

+Introduction
+============
+
+The more-sophisticated device-mapper targets require complex metadata
+that is managed in kernel.  In late 2010 we were seeing that various
+different targets were rolling their own data strutures, for example:
+
+- Mikulas Patocka's multisnap implementation
+- Heinz Mauelshagen's thin provisioning target
+- Another btree-based caching target posted to dm-devel
+- Another multi-snapshot target based on a design of Daniel Phillips
+
+Maintaining these data structures takes a lot of work, so if possible
+we'd like to reduce the number.
+
+The persistent-data library is an attempt to provide a re-usable
+framework for people who want to store metadata in device-mapper
+targets.  It's currently used by the thin-provisioning target and an
+upcoming hierarchical storage target.
+
+Overview
+========
+
+The main documentation is in the header files which can all be found
+under drivers/md/persistent-data.
+
+The block manager
+-----------------
+
+dm-block-manager.[hc]
+
+This provides access to the data on disk in fixed sized-blocks.  There
+is a read/write locking interface to prevent concurrent accesses, and
+keep data that is being used in the cache.
+
+Clients of persistent-data are unlikely to use this directly.
+
+The transaction manager
+-----------------------
+
+dm-transaction-manager.[hc]
+
+This restricts access to blocks and enforces copy-on-write semantics.
+The only way you can get hold of a writable block through the
+transaction manager is by shadowing an existing block (ie. doing
+copy-on-write) or allocating a fresh one.  Shadowing is elided within
+the same transaction so performance is reasonable.  The commit method
+ensures that all data is flushed before it writes the superblock.
+On power failure your metadata will be as it was when last committed.
+
+The Space Maps
+--------------
+
+dm-space-map.h
+dm-space-map-metadata.[hc]
+dm-space-map-disk.[hc]
+
+On-disk data structures that keep track of reference counts of blocks.
+Also acts as the allocator of new blocks.  Currently two
+implementations: a simpler one for managing blocks on a different
+device (eg. thinly-provisioned data blocks); and one for managing
+the metadata space.  The latter is complicated by the need to store
+its own data within the space it's managing.
+
+The data structures
+-------------------
+
+dm-btree.[hc]
+dm-btree-remove.c
+dm-btree-spine.c
+dm-btree-internal.h
+
+Currently there is only one data structure, a hierarchical btree.
+There are plans to add more.  For example, something with an
+array-like interface would see a lot of use.
+
+The btree is 'hierarchical' in that you can define it to be composed
+of nested btrees, and take multiple keys.  For example, the
+thin-provisioning target uses a btree with two levels of nesting.
+The first maps a device id to a mapping tree, and that in turn maps a
+virtual block to a physical block.
+
+Values stored in the btrees can have arbitrary size.  Keys are always
+64bits, although nesting allows you to use multiple keys.

Documentation/device-mapper/thin-provisioning.txt

+Introduction
+============
+
+This document descibes a collection of device-mapper targets that
+between them implement thin-provisioning and snapshots.
+
+The main highlight of this implementation, compared to the previous
+implementation of snapshots, is that it allows many virtual devices to
+be stored on the same data volume.  This simplifies administration and
+allows the sharing of data between volumes, thus reducing disk usage.
+
+Another significant feature is support for an arbitrary depth of
+recursive snapshots (snapshots of snapshots of snapshots ...).  The
+previous implementation of snapshots did this by chaining together
+lookup tables, and so performance was O(depth).  This new
+implementation uses a single data structure to avoid this degradation
+with depth.  Fragmentation may still be an issue, however, in some
+scenarios.
+
+Metadata is stored on a separate device from data, giving the
+administrator some freedom, for example to:
+
+- Improve metadata resilience by storing metadata on a mirrored volume
+  but data on a non-mirrored one.
+
+- Improve performance by storing the metadata on SSD.
+
+Status
+======
+
+These targets are very much still in the EXPERIMENTAL state.  Please
+do not yet rely on them in production.  But do experiment and offer us
+feedback.  Different use cases will have different performance
+characteristics, for example due to fragmentation of the data volume.
+
+If you find this software is not performing as expected please mail
+dm-devel@redhat.com with details and we'll try our best to improve
+things for you.
+
+Userspace tools for checking and repairing the metadata are under
+development.
+
+Cookbook
+========
+
+This section describes some quick recipes for using thin provisioning.
+They use the dmsetup program to control the device-mapper driver
+directly.  End users will be advised to use a higher-level volume
+manager such as LVM2 once support has been added.
+
+Pool device
+-----------
+
+The pool device ties together the metadata volume and the data volume.
+It maps I/O linearly to the data volume and updates the metadata via
+two mechanisms:
+
+- Function calls from the thin targets
+
+- Device-mapper 'messages' from userspace which control the creation of new
+  virtual devices amongst other things.
+
+Setting up a fresh pool device
+------------------------------
+
+Setting up a pool device requires a valid metadata device, and a
+data device.  If you do not have an existing metadata device you can
+make one by zeroing the first 4k to indicate empty metadata.
+
+    dd if=/dev/zero of=$metadata_dev bs=4096 count=1
+
+The amount of metadata you need will vary according to how many blocks
+are shared between thin devices (i.e. through snapshots).  If you have
+less sharing than average you'll need a larger-than-average metadata device.
+
+As a guide, we suggest you calculate the number of bytes to use in the
+metadata device as 48 * $data_dev_size / $data_block_size but round it up
+to 2MB if the answer is smaller.  The largest size supported is 16GB.
+
+If you're creating large numbers of snapshots which are recording large
+amounts of change, you may need find you need to increase this.
+
+Reloading a pool table
+----------------------
+
+You may reload a pool's table, indeed this is how the pool is resized
+if it runs out of space.  (N.B. While specifying a different metadata
+device when reloading is not forbidden at the moment, things will go
+wrong if it does not route I/O to exactly the same on-disk location as
+previously.)
+
+Using an existing pool device
+-----------------------------
+
+    dmsetup create pool \
+	--table "0 20971520 thin-pool $metadata_dev $data_dev \
+		 $data_block_size $low_water_mark"
+
+$data_block_size gives the smallest unit of disk space that can be
+allocated at a time expressed in units of 512-byte sectors.  People
+primarily interested in thin provisioning may want to use a value such
+as 1024 (512KB).  People doing lots of snapshotting may want a smaller value
+such as 128 (64KB).  If you are not zeroing newly-allocated data,
+a larger $data_block_size in the region of 256000 (128MB) is suggested.
+$data_block_size must be the same for the lifetime of the
+metadata device.
+
+$low_water_mark is expressed in blocks of size $data_block_size.  If
+free space on the data device drops below this level then a dm event
+will be triggered which a userspace daemon should catch allowing it to
+extend the pool device.  Only one such event will be sent.
+Resuming a device with a new table itself triggers an event so the
+userspace daemon can use this to detect a situation where a new table
+already exceeds the threshold.
+
+Thin provisioning
+-----------------
+
+i) Creating a new thinly-provisioned volume.
+
+  To create a new thinly- provisioned volume you must send a message to an
+  active pool device, /dev/mapper/pool in this example.
+
+    dmsetup message /dev/mapper/pool 0 "create_thin 0"
+
+  Here '0' is an identifier for the volume, a 24-bit number.  It's up
+  to the caller to allocate and manage these identifiers.  If the
+  identifier is already in use, the message will fail with -EEXIST.
+
+ii) Using a thinly-provisioned volume.
+
+  Thinly-provisioned volumes are activated using the 'thin' target:
+
+    dmsetup create thin --table "0 2097152 thin /dev/mapper/pool 0"
+
+  The last parameter is the identifier for the thinp device.
+
+Internal snapshots
+------------------
+
+i) Creating an internal snapshot.
+
+  Snapshots are created with another message to the pool.
+
+  N.B.  If the origin device that you wish to snapshot is active, you
+  must suspend it before creating the snapshot to avoid corruption.
+  This is NOT enforced at the moment, so please be careful!
+
+    dmsetup suspend /dev/mapper/thin
+    dmsetup message /dev/mapper/pool 0 "create_snap 1 0"
+    dmsetup resume /dev/mapper/thin
+
+  Here '1' is the identifier for the volume, a 24-bit number.  '0' is the
+  identifier for the origin device.
+
+ii) Using an internal snapshot.
+
+  Once created, the user doesn't have to worry about any connection
+  between the origin and the snapshot.  Indeed the snapshot is no
+  different from any other thinly-provisioned device and can be
+  snapshotted itself via the same method.  It's perfectly legal to
+  have only one of them active, and there's no ordering requirement on
+  activating or removing them both.  (This differs from conventional
+  device-mapper snapshots.)
+
+  Activate it exactly the same way as any other thinly-provisioned volume:
+
+    dmsetup create snap --table "0 2097152 thin /dev/mapper/pool 1"
+
+Deactivation
+------------
+
+All devices using a pool must be deactivated before the pool itself
+can be.
+
+    dmsetup remove thin
+    dmsetup remove snap
+    dmsetup remove pool
+
+Reference
+=========
+
+'thin-pool' target
+------------------
+
+i) Constructor
+
+    thin-pool <metadata dev> <data dev> <data block size (sectors)> \
+	      <low water mark (blocks)> [<number of feature args> [<arg>]*]
+
+    Optional feature arguments:
+    - 'skip_block_zeroing': skips the zeroing of newly-provisioned blocks.
+
+    Data block size must be between 64KB (128 sectors) and 1GB
+    (2097152 sectors) inclusive.
+
+
+ii) Status
+
+    <transaction id> <used metadata blocks>/<total metadata blocks>
+    <used data blocks>/<total data blocks> <held metadata root>
+
+
+    transaction id:
+	A 64-bit number used by userspace to help synchronise with metadata
+	from volume managers.
+
+    used data blocks / total data blocks
+	If the number of free blocks drops below the pool's low water mark a
+	dm event will be sent to userspace.  This event is edge-triggered and
+	it will occur only once after each resume so volume manager writers
+	should register for the event and then check the target's status.
+
+    held metadata root:
+	The location, in sectors, of the metadata root that has been
+	'held' for userspace read access.  '-' indicates there is no
+	held root.  This feature is not yet implemented so '-' is
+	always returned.
+
+iii) Messages
+
+    create_thin <dev id>
+
+	Create a new thinly-provisioned device.
+	<dev id> is an arbitrary unique 24-bit identifier chosen by
+	the caller.
+
+    create_snap <dev id> <origin id>
+
+	Create a new snapshot of another thinly-provisioned device.
+	<dev id> is an arbitrary unique 24-bit identifier chosen by
+	the caller.
+	<origin id> is the identifier of the thinly-provisioned device
+	of which the new device will be a snapshot.
+
+    delete <dev id>
+
+	Deletes a thin device.  Irreversible.
+
+    trim <dev id> <new size in sectors>
+
+	Delete mappings from the end of a thin device.  Irreversible.
+	You might want to use this if you're reducing the size of
+	your thinly-provisioned device.  In many cases, due to the
+	sharing of blocks between devices, it is not possible to
+	determine in advance how much space 'trim' will release.  (In
+	future a userspace tool might be able to perform this
+	calculation.)
+
+    set_transaction_id <current id> <new id>
+
+	Userland volume managers, such as LVM, need a way to
+	synchronise their external metadata with the internal metadata of the
+	pool target.  The thin-pool target offers to store an
+	arbitrary 64-bit transaction id and return it on the target's
+	status line.  To avoid races you must provide what you think
+	the current transaction id is when you change it with this
+	compare-and-swap message.
+
+'thin' target
+-------------
+
+i) Constructor
+
+    thin <pool dev> <dev id>
+
+    pool dev:
+	the thin-pool device, e.g. /dev/mapper/my_pool or 253:0
+
+    dev id:
+	the internal device identifier of the device to be
+	activated.
+
+The pool doesn't store any size against the thin devices.  If you
+load a thin target that is smaller than you've been using previously,
+then you'll have no access to blocks mapped beyond the end.  If you
+load a target that is bigger than before, then extra blocks will be
+provisioned as and when needed.
+
+If you wish to reduce the size of your thin device and potentially
+regain some space then send the 'trim' message to the pool.
+
+ii) Status
+
+     <nr mapped sectors> <highest mapped sector>

drivers/md/Kconfig

@@ -208,6 +208,16 @@ config DM_DEBUG
 
 	  If unsure, say N.
 
+config DM_BUFIO
+       tristate
+       depends on BLK_DEV_DM && EXPERIMENTAL
+       ---help---
+	 This interface allows you to do buffered I/O on a device and acts
+	 as a cache, holding recently-read blocks in memory and performing
+	 delayed writes.
+
+source "drivers/md/persistent-data/Kconfig"
+
 config DM_CRYPT
 	tristate "Crypt target support"
 	depends on BLK_DEV_DM
@@ -233,6 +243,32 @@ config DM_SNAPSHOT
        ---help---
          Allow volume managers to take writable snapshots of a device.
 
+config DM_THIN_PROVISIONING
+       tristate "Thin provisioning target (EXPERIMENTAL)"
+       depends on BLK_DEV_DM && EXPERIMENTAL
+       select DM_PERSISTENT_DATA
+       ---help---
+         Provides thin provisioning and snapshots that share a data store.
+
+config DM_DEBUG_BLOCK_STACK_TRACING
+	boolean "Keep stack trace of thin provisioning block lock holders"
+	depends on STACKTRACE_SUPPORT && DM_THIN_PROVISIONING
+	select STACKTRACE
+	---help---
+	  Enable this for messages that may help debug problems with the
+	  block manager locking used by thin provisioning.
+
+	  If unsure, say N.
+
+config DM_DEBUG_SPACE_MAPS
+	boolean "Extra validation for thin provisioning space maps"
+	depends on DM_THIN_PROVISIONING
+	---help---
+	  Enable this for messages that may help debug problems with the
+	  space maps used by thin provisioning.
+
+          If unsure, say N.
+
 config DM_MIRROR
        tristate "Mirror target"
        depends on BLK_DEV_DM

drivers/md/Makefile

@@ -10,6 +10,7 @@ dm-snapshot-y	+= dm-snap.o dm-exception-store.o dm-snap-transient.o \
 dm-mirror-y	+= dm-raid1.o
 dm-log-userspace-y \
 		+= dm-log-userspace-base.o dm-log-userspace-transfer.o
+dm-thin-pool-y	+= dm-thin.o dm-thin-metadata.o
 md-mod-y	+= md.o bitmap.o
 raid456-y	+= raid5.o
 
@@ -27,6 +28,7 @@ obj-$(CONFIG_MD_MULTIPATH)	+= multipath.o
 obj-$(CONFIG_MD_FAULTY)		+= faulty.o
 obj-$(CONFIG_BLK_DEV_MD)	+= md-mod.o
 obj-$(CONFIG_BLK_DEV_DM)	+= dm-mod.o
+obj-$(CONFIG_DM_BUFIO)		+= dm-bufio.o
 obj-$(CONFIG_DM_CRYPT)		+= dm-crypt.o
 obj-$(CONFIG_DM_DELAY)		+= dm-delay.o
 obj-$(CONFIG_DM_FLAKEY)		+= dm-flakey.o
@@ -34,10 +36,12 @@ obj-$(CONFIG_DM_MULTIPATH)	+= dm-multipath.o dm-round-robin.o
 obj-$(CONFIG_DM_MULTIPATH_QL)	+= dm-queue-length.o
 obj-$(CONFIG_DM_MULTIPATH_ST)	+= dm-service-time.o
 obj-$(CONFIG_DM_SNAPSHOT)	+= dm-snapshot.o
+obj-$(CONFIG_DM_PERSISTENT_DATA)	+= persistent-data/
 obj-$(CONFIG_DM_MIRROR)		+= dm-mirror.o dm-log.o dm-region-hash.o
 obj-$(CONFIG_DM_LOG_USERSPACE)	+= dm-log-userspace.o
 obj-$(CONFIG_DM_ZERO)		+= dm-zero.o
 obj-$(CONFIG_DM_RAID)	+= dm-raid.o
+obj-$(CONFIG_DM_THIN_PROVISIONING)	+= dm-thin-pool.o
 
 ifeq ($(CONFIG_DM_UEVENT),y)
 dm-mod-objs			+= dm-uevent.o

drivers/md/dm-bufio.h

+/*
+ * Copyright (C) 2009-2011 Red Hat, Inc.
+ *
+ * Author: Mikulas Patocka <mpatocka@redhat.com>
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_BUFIO_H
+#define DM_BUFIO_H
+
+#include <linux/blkdev.h>
+#include <linux/types.h>
+
+/*----------------------------------------------------------------*/
+
+struct dm_bufio_client;
+struct dm_buffer;
+
+/*
+ * Create a buffered IO cache on a given device
+ */
+struct dm_bufio_client *
+dm_bufio_client_create(struct block_device *bdev, unsigned block_size,
+		       unsigned reserved_buffers, unsigned aux_size,
+		       void (*alloc_callback)(struct dm_buffer *),
+		       void (*write_callback)(struct dm_buffer *));
+
+/*
+ * Release a buffered IO cache.
+ */
+void dm_bufio_client_destroy(struct dm_bufio_client *c);
+
+/*
+ * WARNING: to avoid deadlocks, these conditions are observed:
+ *
+ * - At most one thread can hold at most "reserved_buffers" simultaneously.
+ * - Each other threads can hold at most one buffer.
+ * - Threads which call only dm_bufio_get can hold unlimited number of
+ *   buffers.
+ */
+
+/*
+ * Read a given block from disk. Returns pointer to data.  Returns a
+ * pointer to dm_buffer that can be used to release the buffer or to make
+ * it dirty.
+ */
+void *dm_bufio_read(struct dm_bufio_client *c, sector_t block,
+		    struct dm_buffer **bp);
+
+/*
+ * Like dm_bufio_read, but return buffer from cache, don't read
+ * it. If the buffer is not in the cache, return NULL.
+ */
+void *dm_bufio_get(struct dm_bufio_client *c, sector_t block,
+		   struct dm_buffer **bp);
+
+/*
+ * Like dm_bufio_read, but don't read anything from the disk.  It is
+ * expected that the caller initializes the buffer and marks it dirty.
+ */
+void *dm_bufio_new(struct dm_bufio_client *c, sector_t block,
+		   struct dm_buffer **bp);
+
+/*
+ * Release a reference obtained with dm_bufio_{read,get,new}. The data
+ * pointer and dm_buffer pointer is no longer valid after this call.
+ */
+void dm_bufio_release(struct dm_buffer *b);
+
+/*
+ * Mark a buffer dirty. It should be called after the buffer is modified.
+ *
+ * In case of memory pressure, the buffer may be written after
+ * dm_bufio_mark_buffer_dirty, but before dm_bufio_write_dirty_buffers.  So
+ * dm_bufio_write_dirty_buffers guarantees that the buffer is on-disk but
+ * the actual writing may occur earlier.
+ */
+void dm_bufio_mark_buffer_dirty(struct dm_buffer *b);
+
+/*
+ * Initiate writing of dirty buffers, without waiting for completion.
+ */
+void dm_bufio_write_dirty_buffers_async(struct dm_bufio_client *c);
+
+/*
+ * Write all dirty buffers. Guarantees that all dirty buffers created prior
+ * to this call are on disk when this call exits.
+ */
+int dm_bufio_write_dirty_buffers(struct dm_bufio_client *c);
+
+/*
+ * Send an empty write barrier to the device to flush hardware disk cache.
+ */
+int dm_bufio_issue_flush(struct dm_bufio_client *c);
+
+/*
+ * Like dm_bufio_release but also move the buffer to the new
+ * block. dm_bufio_write_dirty_buffers is needed to commit the new block.
+ */
+void dm_bufio_release_move(struct dm_buffer *b, sector_t new_block);
+
+unsigned dm_bufio_get_block_size(struct dm_bufio_client *c);
+sector_t dm_bufio_get_device_size(struct dm_bufio_client *c);
+sector_t dm_bufio_get_block_number(struct dm_buffer *b);
+void *dm_bufio_get_block_data(struct dm_buffer *b);
+void *dm_bufio_get_aux_data(struct dm_buffer *b);
+struct dm_bufio_client *dm_bufio_get_client(struct dm_buffer *b);
+
+/*----------------------------------------------------------------*/
+
+#endif

drivers/md/dm-ioctl.c

@@ -1215,6 +1215,7 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
 	struct hash_cell *hc;
 	struct dm_table *t;
 	struct mapped_device *md;
+	struct target_type *immutable_target_type;
 
 	md = find_device(param);
 	if (!md)
@@ -1230,6 +1231,16 @@ static int table_load(struct dm_ioctl *param, size_t param_size)
 		goto out;
 	}
 
+	immutable_target_type = dm_get_immutable_target_type(md);
+	if (immutable_target_type &&
+	    (immutable_target_type != dm_table_get_immutable_target_type(t))) {
+		DMWARN("can't replace immutable target type %s",
+		       immutable_target_type->name);
+		dm_table_destroy(t);
+		r = -EINVAL;
+		goto out;
+	}
+
 	/* Protect md->type and md->queue against concurrent table loads. */
 	dm_lock_md_type(md);
 	if (dm_get_md_type(md) == DM_TYPE_NONE)

drivers/md/dm-kcopyd.c

@@ -66,6 +66,8 @@ struct dm_kcopyd_client {
 	struct list_head pages_jobs;
 };
 
+static struct page_list zero_page_list;
+
 static void wake(struct dm_kcopyd_client *kc)
 {
 	queue_work(kc->kcopyd_wq, &kc->kcopyd_work);
@@ -254,6 +256,9 @@ int __init dm_kcopyd_init(void)
 	if (!_job_cache)
 		return -ENOMEM;
 
+	zero_page_list.next = &zero_page_list;
+	zero_page_list.page = ZERO_PAGE(0);
+
 	return 0;
 }
 
@@ -322,7 +327,7 @@ static int run_complete_job(struct kcopyd_job *job)
 	dm_kcopyd_notify_fn fn = job->fn;
 	struct dm_kcopyd_client *kc = job->kc;
 
-	if (job->pages)
+	if (job->pages && job->pages != &zero_page_list)
 		kcopyd_put_pages(kc, job->pages);
 	/*
 	 * If this is the master job, the sub jobs have already
@@ -484,6 +489,8 @@ static void dispatch_job(struct kcopyd_job *job)
 	atomic_inc(&kc->nr_jobs);
 	if (unlikely(!job->source.count))
 		push(&kc->complete_jobs, job);
+	else if (job->pages == &zero_page_list)
+		push(&kc->io_jobs, job);
 	else
 		push(&kc->pages_jobs, job);
 	wake(kc);
@@ -592,14 +599,20 @@ int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
 	job->flags = flags;
 	job->read_err = 0;
 	job->write_err = 0;
-	job->rw = READ;
-
-	job->source = *from;
 
 	job->num_dests = num_dests;
 	memcpy(&job->dests, dests, sizeof(*dests) * num_dests);
 
-	job->pages = NULL;
+	if (from) {
+		job->source = *from;
+		job->pages = NULL;
+		job->rw = READ;
+	} else {
+		memset(&job->source, 0, sizeof job->source);
+		job->source.count = job->dests[0].count;
+		job->pages = &zero_page_list;
+		job->rw = WRITE;
+	}
 
 	job->fn = fn;
 	job->context = context;
@@ -617,6 +630,14 @@ int dm_kcopyd_copy(struct dm_kcopyd_client *kc, struct dm_io_region *from,
 }
 EXPORT_SYMBOL(dm_kcopyd_copy);
 
+int dm_kcopyd_zero(struct dm_kcopyd_client *kc,
+		   unsigned num_dests, struct dm_io_region *dests,
+		   unsigned flags, dm_kcopyd_notify_fn fn, void *context)
+{
+	return dm_kcopyd_copy(kc, NULL, num_dests, dests, flags, fn, context);
+}
+EXPORT_SYMBOL(dm_kcopyd_zero);
+
 void *dm_kcopyd_prepare_callback(struct dm_kcopyd_client *kc,
 				 dm_kcopyd_notify_fn fn, void *context)
 {

drivers/md/dm-log-userspace-base.c

@@ -30,6 +30,7 @@ struct flush_entry {
 
 struct log_c {
 	struct dm_target *ti;
+	struct dm_dev *log_dev;
 	uint32_t region_size;
 	region_t region_count;
 	uint64_t luid;
@@ -146,7 +147,7 @@ static int build_constructor_string(struct dm_target *ti,
  *	<UUID> <other args>
  * Where 'other args' is the userspace implementation specific log
  * arguments.  An example might be:
- *	<UUID> clustered_disk <arg count> <log dev> <region_size> [[no]sync]
+ *	<UUID> clustered-disk <arg count> <log dev> <region_size> [[no]sync]
  *
  * So, this module will strip off the <UUID> for identification purposes
  * when communicating with userspace about a log; but will pass on everything
@@ -161,13 +162,15 @@ static int userspace_ctr(struct dm_dirty_log *log, struct dm_target *ti,
 	struct log_c *lc = NULL;
 	uint64_t rdata;
 	size_t rdata_size = sizeof(rdata);
+	char *devices_rdata = NULL;
+	size_t devices_rdata_size = DM_NAME_LEN;
 
 	if (argc < 3) {
 		DMWARN("Too few arguments to userspace dirty log");
 		return -EINVAL;
 	}
 
-	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
+	lc = kzalloc(sizeof(*lc), GFP_KERNEL);
 	if (!lc) {
 		DMWARN("Unable to allocate userspace log context.");
 		return -ENOMEM;
@@ -195,9 +198,19 @@ static int userspace_ctr(struct dm_dirty_log *log, struct dm_target *ti,
 		return str_size;
 	}
 
-	/* Send table string */
+	devices_rdata = kzalloc(devices_rdata_size, GFP_KERNEL);
+	if (!devices_rdata) {
+		DMERR("Failed to allocate memory for device information");
+		r = -ENOMEM;
+		goto out;
+	}
+
+	/*
+	 * Send table string and get back any opened device.
+	 */
 	r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_CTR,
-				 ctr_str, str_size, NULL, NULL);
+				 ctr_str, str_size,
+				 devices_rdata, &devices_rdata_size);
 
 	if (r < 0) {
 		if (r == -ESRCH)
@@ -220,7 +233,20 @@ static int userspace_ctr(struct dm_dirty_log *log, struct dm_target *ti,
 	lc->region_size = (uint32_t)rdata;
 	lc->region_count = dm_sector_div_up(ti->len, lc->region_size);
 
+	if (devices_rdata_size) {
+		if (devices_rdata[devices_rdata_size - 1] != '\0') {
+			DMERR("DM_ULOG_CTR device return string not properly terminated");
+			r = -EINVAL;
+			goto out;
+		}
+		r = dm_get_device(ti, devices_rdata,
+				  dm_table_get_mode(ti->table), &lc->log_dev);
+		if (r)
+			DMERR("Failed to register %s with device-mapper",
+			      devices_rdata);
+	}
 out:
+	kfree(devices_rdata);
 	if (r) {
 		kfree(lc);
 		kfree(ctr_str);
@@ -241,6 +267,9 @@ static void userspace_dtr(struct dm_dirty_log *log)
 				 NULL, 0,
 				 NULL, NULL);
 
+	if (lc->log_dev)
+		dm_put_device(lc->ti, lc->log_dev);
+
 	kfree(lc->usr_argv_str);
 	kfree(lc);
 

drivers/md/dm-raid.c

@@ -1017,30 +1017,56 @@ static int raid_status(struct dm_target *ti, status_type_t type,
 	struct raid_set *rs = ti->private;
 	unsigned raid_param_cnt = 1; /* at least 1 for chunksize */
 	unsigned sz = 0;
-	int i;
+	int i, array_in_sync = 0;
 	sector_t sync;
 
 	switch (type) {
 	case STATUSTYPE_INFO:
 		DMEMIT("%s %d ", rs->raid_type->name, rs->md.raid_disks);
 
-		for (i = 0; i < rs->md.raid_disks; i++) {
-			if (test_bit(Faulty, &rs->dev[i].rdev.flags))
-				DMEMIT("D");
-			else if (test_bit(In_sync, &rs->dev[i].rdev.flags))
-				DMEMIT("A");
-			else
-				DMEMIT("a");
-		}
-
 		if (test_bit(MD_RECOVERY_RUNNING, &rs->md.recovery))
 			sync = rs->md.curr_resync_completed;
 		else
 			sync = rs->md.recovery_cp;
 
-		if (sync > rs->md.resync_max_sectors)
+		if (sync >= rs->md.resync_max_sectors) {
+			array_in_sync = 1;
 			sync = rs->md.resync_max_sectors;
+		} else {
+			/*
+			 * The array may be doing an initial sync, or it may
+			 * be rebuilding individual components.  If all the
+			 * devices are In_sync, then it is the array that is
+			 * being initialized.
+			 */
+			for (i = 0; i < rs->md.raid_disks; i++)
+				if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
+					array_in_sync = 1;
+		}
+		/*
+		 * Status characters:
+		 *  'D' = Dead/Failed device
+		 *  'a' = Alive but not in-sync
+		 *  'A' = Alive and in-sync
+		 */
+		for (i = 0; i < rs->md.raid_disks; i++) {
+			if (test_bit(Faulty, &rs->dev[i].rdev.flags))
+				DMEMIT("D");
+			else if (!array_in_sync ||
+				 !test_bit(In_sync, &rs->dev[i].rdev.flags))
+				DMEMIT("a");
+			else
+				DMEMIT("A");
+		}
 
+		/*
+		 * In-sync ratio:
+		 *  The in-sync ratio shows the progress of:
+		 *   - Initializing the array
+		 *   - Rebuilding a subset of devices of the array
+		 *  The user can distinguish between the two by referring
+		 *  to the status characters.
+		 */
 		DMEMIT(" %llu/%llu",
 		       (unsigned long long) sync,
 		       (unsigned long long) rs->md.resync_max_sectors);

drivers/md/dm-table.c

@@ -54,7 +54,9 @@ struct dm_table {
 	sector_t *highs;
 	struct dm_target *targets;
 
+	struct target_type *immutable_target_type;
 	unsigned integrity_supported:1;
+	unsigned singleton:1;
 
 	/*
 	 * Indicates the rw permissions for the new logical
@@ -740,6 +742,12 @@ int dm_table_add_target(struct dm_table *t, const char *type,
 	char **argv;
 	struct dm_target *tgt;
 
+	if (t->singleton) {
+		DMERR("%s: target type %s must appear alone in table",
+		      dm_device_name(t->md), t->targets->type->name);
+		return -EINVAL;
+	}
+
 	if ((r = check_space(t)))
 		return r;
 
@@ -758,6 +766,36 @@ int dm_table_add_target(struct dm_table *t, const char *type,
 		return -EINVAL;
 	}
 
+	if (dm_target_needs_singleton(tgt->type)) {
+		if (t->num_targets) {
+			DMERR("%s: target type %s must appear alone in table",
+			      dm_device_name(t->md), type);
+			return -EINVAL;
+		}
+		t->singleton = 1;
+	}
+
+	if (dm_target_always_writeable(tgt->type) && !(t->mode & FMODE_WRITE)) {
+		DMERR("%s: target type %s may not be included in read-only tables",
+		      dm_device_name(t->md), type);
+		return -EINVAL;
+	}
+
+	if (t->immutable_target_type) {
+		if (t->immutable_target_type != tgt->type) {
+			DMERR("%s: immutable target type %s cannot be mixed with other target types",
+			      dm_device_name(t->md), t->immutable_target_type->name);
+			return -EINVAL;
+		}
+	} else if (dm_target_is_immutable(tgt->type)) {
+		if (t->num_targets) {
+			DMERR("%s: immutable target type %s cannot be mixed with other target types",
+			      dm_device_name(t->md), tgt->type->name);
+			return -EINVAL;
+		}
+		t->immutable_target_type = tgt->type;
+	}
+
 	tgt->table = t;
 	tgt->begin = start;
 	tgt->len = len;
@@ -915,6 +953,11 @@ unsigned dm_table_get_type(struct dm_table *t)
 	return t->type;
 }
 
+struct target_type *dm_table_get_immutable_target_type(struct dm_table *t)
+{
+	return t->immutable_target_type;
+}
+
 bool dm_table_request_based(struct dm_table *t)
 {
 	return dm_table_get_type(t) == DM_TYPE_REQUEST_BASED;
@@ -1299,6 +1342,31 @@ static bool dm_table_discard_zeroes_data(struct dm_table *t)
 	return 1;
 }
 
+static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev,
+			    sector_t start, sector_t len, void *data)
+{
+	struct request_queue *q = bdev_get_queue(dev->bdev);
+
+	return q && blk_queue_nonrot(q);
+}
+
+static bool dm_table_is_nonrot(struct dm_table *t)
+{
+	struct dm_target *ti;
+	unsigned i = 0;
+
+	/* Ensure that all underlying device are non-rotational. */
+	while (i < dm_table_get_num_targets(t)) {
+		ti = dm_table_get_target(t, i++);
+
+		if (!ti->type->iterate_devices ||
+		    !ti->type->iterate_devices(ti, device_is_nonrot, NULL))
+			return 0;
+	}
+
+	return 1;
+}
+
 void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 			       struct queue_limits *limits)
 {
@@ -1324,6 +1392,11 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
 	if (!dm_table_discard_zeroes_data(t))
 		q->limits.discard_zeroes_data = 0;
 
+	if (dm_table_is_nonrot(t))
+		queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
+	else
+		queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);
+
 	dm_table_set_integrity(t);
 
 	/*

drivers/md/dm-thin-metadata.h

+/*
+ * Copyright (C) 2010-2011 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_THIN_METADATA_H
+#define DM_THIN_METADATA_H
+
+#include "persistent-data/dm-block-manager.h"
+
+#define THIN_METADATA_BLOCK_SIZE 4096
+
+/*----------------------------------------------------------------*/
+
+struct dm_pool_metadata;
+struct dm_thin_device;
+
+/*
+ * Device identifier
+ */
+typedef uint64_t dm_thin_id;
+
+/*
+ * Reopens or creates a new, empty metadata volume.
+ */
+struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
+					       sector_t data_block_size);
+
+int dm_pool_metadata_close(struct dm_pool_metadata *pmd);
+
+/*
+ * Compat feature flags.  Any incompat flags beyond the ones
+ * specified below will prevent use of the thin metadata.
+ */
+#define THIN_FEATURE_COMPAT_SUPP	  0UL
+#define THIN_FEATURE_COMPAT_RO_SUPP	  0UL
+#define THIN_FEATURE_INCOMPAT_SUPP	  0UL
+
+/*
+ * Device creation/deletion.
+ */
+int dm_pool_create_thin(struct dm_pool_metadata *pmd, dm_thin_id dev);
+
+/*
+ * An internal snapshot.
+ *
+ * You can only snapshot a quiesced origin i.e. one that is either
+ * suspended or not instanced at all.
+ */
+int dm_pool_create_snap(struct dm_pool_metadata *pmd, dm_thin_id dev,
+			dm_thin_id origin);
+
+/*
+ * Deletes a virtual device from the metadata.  It _is_ safe to call this
+ * when that device is open.  Operations on that device will just start
+ * failing.  You still need to call close() on the device.
+ */
+int dm_pool_delete_thin_device(struct dm_pool_metadata *pmd,
+			       dm_thin_id dev);
+
+/*
+ * Commits _all_ metadata changes: device creation, deletion, mapping
+ * updates.
+ */
+int dm_pool_commit_metadata(struct dm_pool_metadata *pmd);
+
+/*
+ * Set/get userspace transaction id.
+ */
+int dm_pool_set_metadata_transaction_id(struct dm_pool_metadata *pmd,
+					uint64_t current_id,
+					uint64_t new_id);
+
+int dm_pool_get_metadata_transaction_id(struct dm_pool_metadata *pmd,
+					uint64_t *result);
+
+/*
+ * Hold/get root for userspace transaction.
+ */
+int dm_pool_hold_metadata_root(struct dm_pool_metadata *pmd);
+
+int dm_pool_get_held_metadata_root(struct dm_pool_metadata *pmd,
+				   dm_block_t *result);
+
+/*
+ * Actions on a single virtual device.
+ */
+
+/*
+ * Opening the same device more than once will fail with -EBUSY.
+ */
+int dm_pool_open_thin_device(struct dm_pool_metadata *pmd, dm_thin_id dev,
+			     struct dm_thin_device **td);
+
+int dm_pool_close_thin_device(struct dm_thin_device *td);
+
+dm_thin_id dm_thin_dev_id(struct dm_thin_device *td);
+
+struct dm_thin_lookup_result {
+	dm_block_t block;
+	int shared;
+};
+
+/*
+ * Returns:
+ *   -EWOULDBLOCK iff @can_block is set and would block.
+ *   -ENODATA iff that mapping is not present.
+ *   0 success
+ */
+int dm_thin_find_block(struct dm_thin_device *td, dm_block_t block,
+		       int can_block, struct dm_thin_lookup_result *result);
+
+/*
+ * Obtain an unused block.
+ */
+int dm_pool_alloc_data_block(struct dm_pool_metadata *pmd, dm_block_t *result);
+
+/*
+ * Insert or remove block.
+ */
+int dm_thin_insert_block(struct dm_thin_device *td, dm_block_t block,
+			 dm_block_t data_block);
+
+int dm_thin_remove_block(struct dm_thin_device *td, dm_block_t block);
+
+/*
+ * Queries.
+ */
+int dm_thin_get_highest_mapped_block(struct dm_thin_device *td,
+				     dm_block_t *highest_mapped);
+
+int dm_thin_get_mapped_count(struct dm_thin_device *td, dm_block_t *result);
+
+int dm_pool_get_free_block_count(struct dm_pool_metadata *pmd,
+				 dm_block_t *result);
+
+int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
+					  dm_block_t *result);
+
+int dm_pool_get_metadata_dev_size(struct dm_pool_metadata *pmd,
+				  dm_block_t *result);
+
+int dm_pool_get_data_block_size(struct dm_pool_metadata *pmd, sector_t *result);
+
+int dm_pool_get_data_dev_size(struct dm_pool_metadata *pmd, dm_block_t *result);
+
+/*
+ * Returns -ENOSPC if the new size is too small and already allocated
+ * blocks would be lost.
+ */
+int dm_pool_resize_data_dev(struct dm_pool_metadata *pmd, dm_block_t new_size);
+
+/*----------------------------------------------------------------*/
+
+#endif

drivers/md/dm.c

@@ -25,6 +25,16 @@
 
 #define DM_MSG_PREFIX "core"
 
+#ifdef CONFIG_PRINTK
+/*
+ * ratelimit state to be used in DMXXX_LIMIT().
+ */
+DEFINE_RATELIMIT_STATE(dm_ratelimit_state,
+		       DEFAULT_RATELIMIT_INTERVAL,
+		       DEFAULT_RATELIMIT_BURST);
+EXPORT_SYMBOL(dm_ratelimit_state);
+#endif
+
 /*
  * Cookies are numeric values sent with CHANGE and REMOVE
  * uevents while resuming, removing or renaming the device.
@@ -130,6 +140,8 @@ struct mapped_device {
 	/* Protect queue and type against concurrent access. */
 	struct mutex type_lock;
 
+	struct target_type *immutable_target_type;
+
 	struct gendisk *disk;
 	char name[16];
 
@@ -2086,6 +2098,8 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
 	write_lock_irqsave(&md->map_lock, flags);
 	old_map = md->map;
 	md->map = t;
+	md->immutable_target_type = dm_table_get_immutable_target_type(t);
+
 	dm_table_set_restrictions(t, q, limits);
 	if (merge_is_optional)
 		set_bit(DMF_MERGE_IS_OPTIONAL, &md->flags);
@@ -2156,6 +2170,11 @@ unsigned dm_get_md_type(struct mapped_device *md)
 	return md->type;
 }
 
+struct target_type *dm_get_immutable_target_type(struct mapped_device *md)
+{
+	return md->immutable_target_type;
+}
+
 /*
  * Fully initialize a request-based queue (->elevator, ->request_fn, etc).
  */
@@ -2231,6 +2250,7 @@ struct mapped_device *dm_get_md(dev_t dev)
 
 	return md;
 }
+EXPORT_SYMBOL_GPL(dm_get_md);
 
 void *dm_get_mdptr(struct mapped_device *md)
 {
@@ -2316,7 +2336,6 @@ static int dm_wait_for_completion(struct mapped_device *md, int interruptible)
 	while (1) {
 		set_current_state(interruptible);
 
-		smp_mb();
 		if (!md_in_flight(md))
 			break;
 

drivers/md/dm.h

@@ -60,6 +60,7 @@ int dm_table_resume_targets(struct dm_table *t);
 int dm_table_any_congested(struct dm_table *t, int bdi_bits);
 int dm_table_any_busy_target(struct dm_table *t);
 unsigned dm_table_get_type(struct dm_table *t);
+struct target_type *dm_table_get_immutable_target_type(struct dm_table *t);
 bool dm_table_request_based(struct dm_table *t);
 bool dm_table_supports_discards(struct dm_table *t);
 int dm_table_alloc_md_mempools(struct dm_table *t);
@@ -72,6 +73,7 @@ void dm_lock_md_type(struct mapped_device *md);
 void dm_unlock_md_type(struct mapped_device *md);
 void dm_set_md_type(struct mapped_device *md, unsigned type);
 unsigned dm_get_md_type(struct mapped_device *md);
+struct target_type *dm_get_immutable_target_type(struct mapped_device *md);
 
 int dm_setup_md_queue(struct mapped_device *md);
 

drivers/md/persistent-data/Kconfig

+config DM_PERSISTENT_DATA
+       tristate
+       depends on BLK_DEV_DM && EXPERIMENTAL
+       select LIBCRC32C
+       select DM_BUFIO
+       ---help---
+	 Library providing immutable on-disk data structure support for
+	 device-mapper targets such as the thin provisioning target.

drivers/md/persistent-data/Makefile

+obj-$(CONFIG_DM_PERSISTENT_DATA) += dm-persistent-data.o
+dm-persistent-data-objs := \
+	dm-block-manager.o \
+	dm-space-map-checker.o \
+	dm-space-map-common.o \
+	dm-space-map-disk.o \
+	dm-space-map-metadata.o \
+	dm-transaction-manager.o \
+	dm-btree.o \
+	dm-btree-remove.o \
+	dm-btree-spine.o

drivers/md/persistent-data/dm-block-manager.c

+/*
+ * Copyright (C) 2011 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+#include "dm-block-manager.h"
+#include "dm-persistent-data-internal.h"
+#include "../dm-bufio.h"
+
+#include <linux/crc32c.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/rwsem.h>
+#include <linux/device-mapper.h>
+#include <linux/stacktrace.h>
+
+#define DM_MSG_PREFIX "block manager"
+
+/*----------------------------------------------------------------*/
+
+/*
+ * This is a read/write semaphore with a couple of differences.
+ *
+ * i) There is a restriction on the number of concurrent read locks that
+ * may be held at once.  This is just an implementation detail.
+ *
+ * ii) Recursive locking attempts are detected and return EINVAL.  A stack
+ * trace is also emitted for the previous lock aquisition.
+ *
+ * iii) Priority is given to write locks.
+ */
+#define MAX_HOLDERS 4
+#define MAX_STACK 10
+
+typedef unsigned long stack_entries[MAX_STACK];
+
+struct block_lock {
+	spinlock_t lock;
+	__s32 count;
+	struct list_head waiters;
+	struct task_struct *holders[MAX_HOLDERS];
+
+#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
+	struct stack_trace traces[MAX_HOLDERS];
+	stack_entries entries[MAX_HOLDERS];
+#endif
+};
+
+struct waiter {
+	struct list_head list;
+	struct task_struct *task;
+	int wants_write;
+};
+
+static unsigned __find_holder(struct block_lock *lock,
+			      struct task_struct *task)
+{
+	unsigned i;
+
+	for (i = 0; i < MAX_HOLDERS; i++)
+		if (lock->holders[i] == task)
+			break;
+
+	BUG_ON(i == MAX_HOLDERS);
+	return i;
+}
+
+/* call this *after* you increment lock->count */
+static void __add_holder(struct block_lock *lock, struct task_struct *task)
+{
+	unsigned h = __find_holder(lock, NULL);
+#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
+	struct stack_trace *t;
+#endif
+
+	get_task_struct(task);
+	lock->holders[h] = task;
+
+#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
+	t = lock->traces + h;
+	t->nr_entries = 0;
+	t->max_entries = MAX_STACK;
+	t->entries = lock->entries[h];
+	t->skip = 2;
+	save_stack_trace(t);
+#endif
+}
+
+/* call this *before* you decrement lock->count */
+static void __del_holder(struct block_lock *lock, struct task_struct *task)
+{
+	unsigned h = __find_holder(lock, task);
+	lock->holders[h] = NULL;
+	put_task_struct(task);
+}
+
+static int __check_holder(struct block_lock *lock)
+{
+	unsigned i;
+#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
+	static struct stack_trace t;
+	static stack_entries entries;
+#endif
+
+	for (i = 0; i < MAX_HOLDERS; i++) {
+		if (lock->holders[i] == current) {
+			DMERR("recursive lock detected in pool metadata");
+#ifdef CONFIG_DM_DEBUG_BLOCK_STACK_TRACING
+			DMERR("previously held here:");
+			print_stack_trace(lock->traces + i, 4);
+
+			DMERR("subsequent aquisition attempted here:");
+			t.nr_entries = 0;
+			t.max_entries = MAX_STACK;
+			t.entries = entries;
+			t.skip = 3;
+			save_stack_trace(&t);
+			print_stack_trace(&t, 4);
+#endif
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+static void __wait(struct waiter *w)
+{
+	for (;;) {
+		set_task_state(current, TASK_UNINTERRUPTIBLE);
+
+		if (!w->task)
+			break;
+
+		schedule();
+	}
+
+	set_task_state(current, TASK_RUNNING);
+}
+
+static void __wake_waiter(struct waiter *w)
+{
+	struct task_struct *task;
+
+	list_del(&w->list);
+	task = w->task;
+	smp_mb();
+	w->task = NULL;
+	wake_up_process(task);
+}
+
+/*
+ * We either wake a few readers or a single writer.
+ */
+static void __wake_many(struct block_lock *lock)
+{
+	struct waiter *w, *tmp;
+
+	BUG_ON(lock->count < 0);
+	list_for_each_entry_safe(w, tmp, &lock->waiters, list) {
+		if (lock->count >= MAX_HOLDERS)
+			return;
+
+		if (w->wants_write) {
+			if (lock->count > 0)
+				return; /* still read locked */
+
+			lock->count = -1;
+			__add_holder(lock, w->task);
+			__wake_waiter(w);
+			return;
+		}
+
+		lock->count++;
+		__add_holder(lock, w->task);
+		__wake_waiter(w);
+	}
+}
+
+static void bl_init(struct block_lock *lock)
+{
+	int i;
+
+	spin_lock_init(&lock->lock);
+	lock->count = 0;
+	INIT_LIST_HEAD(&lock->waiters);
+	for (i = 0; i < MAX_HOLDERS; i++)
+		lock->holders[i] = NULL;
+}
+
+static int __available_for_read(struct block_lock *lock)
+{
+	return lock->count >= 0 &&
+		lock->count < MAX_HOLDERS &&
+		list_empty(&lock->waiters);
+}
+
+static int bl_down_read(struct block_lock *lock)
+{
+	int r;
+	struct waiter w;
+
+	spin_lock(&lock->lock);
+	r = __check_holder(lock);
+	if (r) {
+		spin_unlock(&lock->lock);
+		return r;
+	}
+
+	if (__available_for_read(lock)) {
+		lock->count++;
+		__add_holder(lock, current);
+		spin_unlock(&lock->lock);
+		return 0;
+	}
+
+	get_task_struct(current);
+
+	w.task = current;
+	w.wants_write = 0;
+	list_add_tail(&w.list, &lock->waiters);
+	spin_unlock(&lock->lock);
+
+	__wait(&w);
+	put_task_struct(current);
+	return 0;
+}
+
+static int bl_down_read_nonblock(struct block_lock *lock)
+{
+	int r;
+
+	spin_lock(&lock->lock);
+	r = __check_holder(lock);
+	if (r)
+		goto out;
+
+	if (__available_for_read(lock)) {
+		lock->count++;
+		__add_holder(lock, current);
+		r = 0;
+	} else
+		r = -EWOULDBLOCK;
+
+out:
+	spin_unlock(&lock->lock);
+	return r;
+}
+
+static void bl_up_read(struct block_lock *lock)
+{
+	spin_lock(&lock->lock);
+	BUG_ON(lock->count <= 0);
+	__del_holder(lock, current);
+	--lock->count;
+	if (!list_empty(&lock->waiters))
+		__wake_many(lock);
+	spin_unlock(&lock->lock);
+}
+
+static int bl_down_write(struct block_lock *lock)
+{
+	int r;
+	struct waiter w;
+
+	spin_lock(&lock->lock);
+	r = __check_holder(lock);
+	if (r) {
+		spin_unlock(&lock->lock);
+		return r;
+	}
+
+	if (lock->count == 0 && list_empty(&lock->waiters)) {
+		lock->count = -1;
+		__add_holder(lock, current);
+		spin_unlock(&lock->lock);
+		return 0;
+	}
+
+	get_task_struct(current);
+	w.task = current;
+	w.wants_write = 1;
+
+	/*
+	 * Writers given priority. We know there's only one mutator in the
+	 * system, so ignoring the ordering reversal.
+	 */
+	list_add(&w.list, &lock->waiters);
+	spin_unlock(&lock->lock);
+
+	__wait(&w);
+	put_task_struct(current);
+
+	return 0;
+}
+
+static void bl_up_write(struct block_lock *lock)
+{
+	spin_lock(&lock->lock);
+	__del_holder(lock, current);
+	lock->count = 0;
+	if (!list_empty(&lock->waiters))
+		__wake_many(lock);
+	spin_unlock(&lock->lock);
+}
+
+static void report_recursive_bug(dm_block_t b, int r)
+{
+	if (r == -EINVAL)
+		DMERR("recursive acquisition of block %llu requested.",
+		      (unsigned long long) b);
+}
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Block manager is currently implemented using dm-bufio.  struct
+ * dm_block_manager and struct dm_block map directly onto a couple of
+ * structs in the bufio interface.  I want to retain the freedom to move
+ * away from bufio in the future.  So these structs are just cast within
+ * this .c file, rather than making it through to the public interface.
+ */
+static struct dm_buffer *to_buffer(struct dm_block *b)
+{
+	return (struct dm_buffer *) b;
+}
+
+static struct dm_bufio_client *to_bufio(struct dm_block_manager *bm)
+{
+	return (struct dm_bufio_client *) bm;
+}
+
+dm_block_t dm_block_location(struct dm_block *b)
+{
+	return dm_bufio_get_block_number(to_buffer(b));
+}
+EXPORT_SYMBOL_GPL(dm_block_location);
+
+void *dm_block_data(struct dm_block *b)
+{
+	return dm_bufio_get_block_data(to_buffer(b));
+}
+EXPORT_SYMBOL_GPL(dm_block_data);
+
+struct buffer_aux {
+	struct dm_block_validator *validator;
+	struct block_lock lock;
+	int write_locked;
+};
+
+static void dm_block_manager_alloc_callback(struct dm_buffer *buf)
+{
+	struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
+	aux->validator = NULL;
+	bl_init(&aux->lock);
+}
+
+static void dm_block_manager_write_callback(struct dm_buffer *buf)
+{
+	struct buffer_aux *aux = dm_bufio_get_aux_data(buf);
+	if (aux->validator) {
+		aux->validator->prepare_for_write(aux->validator, (struct dm_block *) buf,
+			 dm_bufio_get_block_size(dm_bufio_get_client(buf)));
+	}
+}
+
+/*----------------------------------------------------------------
+ * Public interface
+ *--------------------------------------------------------------*/
+struct dm_block_manager *dm_block_manager_create(struct block_device *bdev,
+						 unsigned block_size,
+						 unsigned cache_size,
+						 unsigned max_held_per_thread)
+{
+	return (struct dm_block_manager *)
+		dm_bufio_client_create(bdev, block_size, max_held_per_thread,
+				       sizeof(struct buffer_aux),
+				       dm_block_manager_alloc_callback,
+				       dm_block_manager_write_callback);
+}
+EXPORT_SYMBOL_GPL(dm_block_manager_create);
+
+void dm_block_manager_destroy(struct dm_block_manager *bm)
+{
+	return dm_bufio_client_destroy(to_bufio(bm));
+}
+EXPORT_SYMBOL_GPL(dm_block_manager_destroy);
+
+unsigned dm_bm_block_size(struct dm_block_manager *bm)
+{
+	return dm_bufio_get_block_size(to_bufio(bm));
+}
+EXPORT_SYMBOL_GPL(dm_bm_block_size);
+
+dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm)
+{
+	return dm_bufio_get_device_size(to_bufio(bm));
+}
+
+static int dm_bm_validate_buffer(struct dm_block_manager *bm,
+				 struct dm_buffer *buf,
+				 struct buffer_aux *aux,
+				 struct dm_block_validator *v)
+{
+	if (unlikely(!aux->validator)) {
+		int r;
+		if (!v)
+			return 0;
+		r = v->check(v, (struct dm_block *) buf, dm_bufio_get_block_size(to_bufio(bm)));
+		if (unlikely(r))
+			return r;
+		aux->validator = v;
+	} else {
+		if (unlikely(aux->validator != v)) {
+			DMERR("validator mismatch (old=%s vs new=%s) for block %llu",
+				aux->validator->name, v ? v->name : "NULL",
+				(unsigned long long)
+					dm_bufio_get_block_number(buf));
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
+		    struct dm_block_validator *v,
+		    struct dm_block **result)
+{
+	struct buffer_aux *aux;
+	void *p;
+	int r;
+
+	p = dm_bufio_read(to_bufio(bm), b, (struct dm_buffer **) result);
+	if (unlikely(IS_ERR(p)))
+		return PTR_ERR(p);
+
+	aux = dm_bufio_get_aux_data(to_buffer(*result));
+	r = bl_down_read(&aux->lock);
+	if (unlikely(r)) {
+		dm_bufio_release(to_buffer(*result));
+		report_recursive_bug(b, r);
+		return r;
+	}
+
+	aux->write_locked = 0;
+
+	r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
+	if (unlikely(r)) {
+		bl_up_read(&aux->lock);
+		dm_bufio_release(to_buffer(*result));
+		return r;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dm_bm_read_lock);
+
+int dm_bm_write_lock(struct dm_block_manager *bm,
+		     dm_block_t b, struct dm_block_validator *v,
+		     struct dm_block **result)
+{
+	struct buffer_aux *aux;
+	void *p;
+	int r;
+
+	p = dm_bufio_read(to_bufio(bm), b, (struct dm_buffer **) result);
+	if (unlikely(IS_ERR(p)))
+		return PTR_ERR(p);
+
+	aux = dm_bufio_get_aux_data(to_buffer(*result));
+	r = bl_down_write(&aux->lock);
+	if (r) {
+		dm_bufio_release(to_buffer(*result));
+		report_recursive_bug(b, r);
+		return r;
+	}
+
+	aux->write_locked = 1;
+
+	r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
+	if (unlikely(r)) {
+		bl_up_write(&aux->lock);
+		dm_bufio_release(to_buffer(*result));
+		return r;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dm_bm_write_lock);
+
+int dm_bm_read_try_lock(struct dm_block_manager *bm,
+			dm_block_t b, struct dm_block_validator *v,
+			struct dm_block **result)
+{
+	struct buffer_aux *aux;
+	void *p;
+	int r;
+
+	p = dm_bufio_get(to_bufio(bm), b, (struct dm_buffer **) result);
+	if (unlikely(IS_ERR(p)))
+		return PTR_ERR(p);
+	if (unlikely(!p))
+		return -EWOULDBLOCK;
+
+	aux = dm_bufio_get_aux_data(to_buffer(*result));
+	r = bl_down_read_nonblock(&aux->lock);
+	if (r < 0) {
+		dm_bufio_release(to_buffer(*result));
+		report_recursive_bug(b, r);
+		return r;
+	}
+	aux->write_locked = 0;
+
+	r = dm_bm_validate_buffer(bm, to_buffer(*result), aux, v);
+	if (unlikely(r)) {
+		bl_up_read(&aux->lock);
+		dm_bufio_release(to_buffer(*result));
+		return r;
+	}
+
+	return 0;
+}
+
+int dm_bm_write_lock_zero(struct dm_block_manager *bm,
+			  dm_block_t b, struct dm_block_validator *v,
+			  struct dm_block **result)
+{
+	int r;
+	struct buffer_aux *aux;
+	void *p;
+
+	p = dm_bufio_new(to_bufio(bm), b, (struct dm_buffer **) result);
+	if (unlikely(IS_ERR(p)))
+		return PTR_ERR(p);
+
+	memset(p, 0, dm_bm_block_size(bm));
+
+	aux = dm_bufio_get_aux_data(to_buffer(*result));
+	r = bl_down_write(&aux->lock);
+	if (r) {
+		dm_bufio_release(to_buffer(*result));
+		return r;
+	}
+
+	aux->write_locked = 1;
+	aux->validator = v;
+
+	return 0;
+}
+
+int dm_bm_unlock(struct dm_block *b)
+{
+	struct buffer_aux *aux;
+	aux = dm_bufio_get_aux_data(to_buffer(b));
+
+	if (aux->write_locked) {
+		dm_bufio_mark_buffer_dirty(to_buffer(b));
+		bl_up_write(&aux->lock);
+	} else
+		bl_up_read(&aux->lock);
+
+	dm_bufio_release(to_buffer(b));
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(dm_bm_unlock);
+
+int dm_bm_unlock_move(struct dm_block *b, dm_block_t n)
+{
+	struct buffer_aux *aux;
+
+	aux = dm_bufio_get_aux_data(to_buffer(b));
+
+	if (aux->write_locked) {
+		dm_bufio_mark_buffer_dirty(to_buffer(b));
+		bl_up_write(&aux->lock);
+	} else
+		bl_up_read(&aux->lock);
+
+	dm_bufio_release_move(to_buffer(b), n);
+	return 0;
+}
+
+int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
+			   struct dm_block *superblock)
+{
+	int r;
+
+	r = dm_bufio_write_dirty_buffers(to_bufio(bm));
+	if (unlikely(r))
+		return r;
+	r = dm_bufio_issue_flush(to_bufio(bm));
+	if (unlikely(r))
+		return r;
+
+	dm_bm_unlock(superblock);
+
+	r = dm_bufio_write_dirty_buffers(to_bufio(bm));
+	if (unlikely(r))
+		return r;
+	r = dm_bufio_issue_flush(to_bufio(bm));
+	if (unlikely(r))
+		return r;
+
+	return 0;
+}
+
+u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor)
+{
+	return crc32c(~(u32) 0, data, len) ^ init_xor;
+}
+EXPORT_SYMBOL_GPL(dm_bm_checksum);
+
+/*----------------------------------------------------------------*/
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
+MODULE_DESCRIPTION("Immutable metadata library for dm");
+
+/*----------------------------------------------------------------*/

drivers/md/persistent-data/dm-block-manager.h

+/*
+ * Copyright (C) 2011 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef _LINUX_DM_BLOCK_MANAGER_H
+#define _LINUX_DM_BLOCK_MANAGER_H
+
+#include <linux/types.h>
+#include <linux/blkdev.h>
+
+/*----------------------------------------------------------------*/
+
+/*
+ * Block number.
+ */
+typedef uint64_t dm_block_t;
+struct dm_block;
+
+dm_block_t dm_block_location(struct dm_block *b);
+void *dm_block_data(struct dm_block *b);
+
+/*----------------------------------------------------------------*/
+
+/*
+ * @name should be a unique identifier for the block manager, no longer
+ * than 32 chars.
+ *
+ * @max_held_per_thread should be the maximum number of locks, read or
+ * write, that an individual thread holds at any one time.
+ */
+struct dm_block_manager;
+struct dm_block_manager *dm_block_manager_create(
+	struct block_device *bdev, unsigned block_size,
+	unsigned cache_size, unsigned max_held_per_thread);
+void dm_block_manager_destroy(struct dm_block_manager *bm);
+
+unsigned dm_bm_block_size(struct dm_block_manager *bm);
+dm_block_t dm_bm_nr_blocks(struct dm_block_manager *bm);
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The validator allows the caller to verify newly-read data and modify
+ * the data just before writing, e.g. to calculate checksums.  It's
+ * important to be consistent with your use of validators.  The only time
+ * you can change validators is if you call dm_bm_write_lock_zero.
+ */
+struct dm_block_validator {
+	const char *name;
+	void (*prepare_for_write)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
+
+	/*
+	 * Return 0 if the checksum is valid or < 0 on error.
+	 */
+	int (*check)(struct dm_block_validator *v, struct dm_block *b, size_t block_size);
+};
+
+/*----------------------------------------------------------------*/
+
+/*
+ * You can have multiple concurrent readers or a single writer holding a
+ * block lock.
+ */
+
+/*
+ * dm_bm_lock() locks a block and returns through @result a pointer to
+ * memory that holds a copy of that block.  If you have write-locked the
+ * block then any changes you make to memory pointed to by @result will be
+ * written back to the disk sometime after dm_bm_unlock is called.
+ */
+int dm_bm_read_lock(struct dm_block_manager *bm, dm_block_t b,
+		    struct dm_block_validator *v,
+		    struct dm_block **result);
+
+int dm_bm_write_lock(struct dm_block_manager *bm, dm_block_t b,
+		     struct dm_block_validator *v,
+		     struct dm_block **result);
+
+/*
+ * The *_try_lock variants return -EWOULDBLOCK if the block isn't
+ * available immediately.
+ */
+int dm_bm_read_try_lock(struct dm_block_manager *bm, dm_block_t b,
+			struct dm_block_validator *v,
+			struct dm_block **result);
+
+/*
+ * Use dm_bm_write_lock_zero() when you know you're going to
+ * overwrite the block completely.  It saves a disk read.
+ */
+int dm_bm_write_lock_zero(struct dm_block_manager *bm, dm_block_t b,
+			  struct dm_block_validator *v,
+			  struct dm_block **result);
+
+int dm_bm_unlock(struct dm_block *b);
+
+/*
+ * An optimisation; we often want to copy a block's contents to a new
+ * block.  eg, as part of the shadowing operation.  It's far better for
+ * bufio to do this move behind the scenes than hold 2 locks and memcpy the
+ * data.
+ */
+int dm_bm_unlock_move(struct dm_block *b, dm_block_t n);
+
+/*
+ * It's a common idiom to have a superblock that should be committed last.
+ *
+ * @superblock should be write-locked on entry. It will be unlocked during
+ * this function.  All dirty blocks are guaranteed to be written and flushed
+ * before the superblock.
+ *
+ * This method always blocks.
+ */
+int dm_bm_flush_and_unlock(struct dm_block_manager *bm,
+			   struct dm_block *superblock);
+
+u32 dm_bm_checksum(const void *data, size_t len, u32 init_xor);
+
+/*----------------------------------------------------------------*/
+
+#endif	/* _LINUX_DM_BLOCK_MANAGER_H */