Merge tag 'dm-3.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm

Pull device-mapper changes for 3.4 from Alasdair Kergon:

 - Update thin provisioning to support read-only external snapshot
   origins and discards.
 - A new target, dm verity, for device content validation.
 - Mark dm uevent and dm raid as no-longer-experimental.
 - Miscellaneous other fixes and clean-ups.

* tag 'dm-3.4-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/agk/linux-dm: (27 commits)
  dm: add verity target
  dm bufio: prefetch
  dm thin: add pool target flags to control discard
  dm thin: support discards
  dm thin: prepare to support discard
  dm thin: use dm_target_offset
  dm thin: support read only external snapshot origins
  dm thin: relax hard limit on the maximum size of a metadata device
  dm persistent data: remove space map ref_count entries if redundant
  dm thin: commit outstanding data every second
  dm: reject trailing characters in sccanf input
  dm raid: handle failed devices during start up
  dm thin metadata: pass correct space map to dm_sm_root_size
  dm persistent data: remove redundant value_size arg from value_ptr
  dm mpath: detect invalid map_context
  dm: clear bi_end_io on remapping failure
  dm table: simplify call to free_devices
  dm thin: correct comments
  dm raid: no longer experimental
  dm uevent: no longer experimental
  ...

3 files changed, 269 insertions, 15 deletions

diff --git a/Documentation/ABI/testing/sysfs-block-dm b/Documentation/ABI/testing/sysfs-block-dm
new file mode 100644
index 00000000000..87ca5691e29
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-block-dm
@@ -0,0 +1,25 @@
+What:		/sys/block/dm-<num>/dm/name
+Date:		January 2009
+KernelVersion:	2.6.29
+Contact:	dm-devel@redhat.com
+Description:	Device-mapper device name.
+		Read-only string containing mapped device name.
+Users:		util-linux, device-mapper udev rules
+
+What:		/sys/block/dm-<num>/dm/uuid
+Date:		January 2009
+KernelVersion:	2.6.29
+Contact:	dm-devel@redhat.com
+Description:	Device-mapper device UUID.
+		Read-only string containing DM-UUID or empty string
+		if DM-UUID is not set.
+Users:		util-linux, device-mapper udev rules
+
+What:		/sys/block/dm-<num>/dm/suspended
+Date:		June 2009
+KernelVersion:	2.6.31
+Contact:	dm-devel@redhat.com
+Description:	Device-mapper device suspend state.
+		Contains the value 1 while the device is suspended.
+		Otherwise it contains 0. Read-only attribute.
+Users:		util-linux, device-mapper udev rules
diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt
index 1ff044d87ca..3370bc4d7b9 100644
--- a/Documentation/device-mapper/thin-provisioning.txt
+++ b/Documentation/device-mapper/thin-provisioning.txt
@@ -75,10 +75,12 @@ 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.
+to 2MB if the answer is smaller.  If you're creating large numbers of
+snapshots which are recording large amounts of change, you may find you
+need to increase this.
 
-If you're creating large numbers of snapshots which are recording large
-amounts of change, you may need find you need to increase this.
+The largest size supported is 16GB: If the device is larger,
+a warning will be issued and the excess space will not be used.
 
 Reloading a pool table
 ----------------------
@@ -167,6 +169,38 @@ ii) Using an internal snapshot.
 
     dmsetup create snap --table "0 2097152 thin /dev/mapper/pool 1"
 
+External snapshots
+------------------
+
+You can use an external _read only_ device as an origin for a
+thinly-provisioned volume.  Any read to an unprovisioned area of the
+thin device will be passed through to the origin.  Writes trigger
+the allocation of new blocks as usual.
+
+One use case for this is VM hosts that want to run guests on
+thinly-provisioned volumes but have the base image on another device
+(possibly shared between many VMs).
+
+You must not write to the origin device if you use this technique!
+Of course, you may write to the thin device and take internal snapshots
+of the thin volume.
+
+i) Creating a snapshot of an external device
+
+  This is the same as creating a thin device.
+  You don't mention the origin at this stage.
+
+    dmsetup message /dev/mapper/pool 0 "create_thin 0"
+
+ii) Using a snapshot of an external device.
+
+  Append an extra parameter to the thin target specifying the origin:
+
+    dmsetup create snap --table "0 2097152 thin /dev/mapper/pool 0 /dev/image"
+
+  N.B. All descendants (internal snapshots) of this snapshot require the
+  same extra origin parameter.
+
 Deactivation
 ------------
 
@@ -189,7 +223,13 @@ i) Constructor
 	      <low water mark (blocks)> [<number of feature args> [<arg>]*]
 
     Optional feature arguments:
-    - 'skip_block_zeroing': skips the zeroing of newly-provisioned blocks.
+
+      skip_block_zeroing: Skip the zeroing of newly-provisioned blocks.
+
+      ignore_discard: Disable discard support.
+
+      no_discard_passdown: Don't pass discards down to the underlying
+			   data device, but just remove the mapping.
 
     Data block size must be between 64KB (128 sectors) and 1GB
     (2097152 sectors) inclusive.
@@ -237,16 +277,6 @@ iii) Messages
 
 	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
@@ -262,7 +292,7 @@ iii) Messages
 
 i) Constructor
 
-    thin <pool dev> <dev id>
+    thin <pool dev> <dev id> [<external origin dev>]
 
     pool dev:
 	the thin-pool device, e.g. /dev/mapper/my_pool or 253:0
@@ -271,6 +301,11 @@ i) Constructor
 	the internal device identifier of the device to be
 	activated.
 
+    external origin dev:
+	an optional block device outside the pool to be treated as a
+	read-only snapshot origin: reads to unprovisioned areas of the
+	thin target will be mapped to this device.
+
 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
diff --git a/Documentation/device-mapper/verity.txt b/Documentation/device-mapper/verity.txt
new file mode 100644
index 00000000000..32e48797a14
--- /dev/null
+++ b/Documentation/device-mapper/verity.txt
@@ -0,0 +1,194 @@
+dm-verity
+==========
+
+Device-Mapper's "verity" target provides transparent integrity checking of
+block devices using a cryptographic digest provided by the kernel crypto API.
+This target is read-only.
+
+Construction Parameters
+=======================
+    <version> <dev> <hash_dev> <hash_start>
+    <data_block_size> <hash_block_size>
+    <num_data_blocks> <hash_start_block>
+    <algorithm> <digest> <salt>
+
+<version>
+    This is the version number of the on-disk format.
+
+    0 is the original format used in the Chromium OS.
+	The salt is appended when hashing, digests are stored continuously and
+	the rest of the block is padded with zeros.
+
+    1 is the current format that should be used for new devices.
+	The salt is prepended when hashing and each digest is
+	padded with zeros to the power of two.
+
+<dev>
+    This is the device containing the data the integrity of which needs to be
+    checked.  It may be specified as a path, like /dev/sdaX, or a device number,
+    <major>:<minor>.
+
+<hash_dev>
+    This is the device that that supplies the hash tree data.  It may be
+    specified similarly to the device path and may be the same device.  If the
+    same device is used, the hash_start should be outside of the dm-verity
+    configured device size.
+
+<data_block_size>
+    The block size on a data device.  Each block corresponds to one digest on
+    the hash device.
+
+<hash_block_size>
+    The size of a hash block.
+
+<num_data_blocks>
+    The number of data blocks on the data device.  Additional blocks are
+    inaccessible.  You can place hashes to the same partition as data, in this
+    case hashes are placed after <num_data_blocks>.
+
+<hash_start_block>
+    This is the offset, in <hash_block_size>-blocks, from the start of hash_dev
+    to the root block of the hash tree.
+
+<algorithm>
+    The cryptographic hash algorithm used for this device.  This should
+    be the name of the algorithm, like "sha1".
+
+<digest>
+    The hexadecimal encoding of the cryptographic hash of the root hash block
+    and the salt.  This hash should be trusted as there is no other authenticity
+    beyond this point.
+
+<salt>
+    The hexadecimal encoding of the salt value.
+
+Theory of operation
+===================
+
+dm-verity is meant to be setup as part of a verified boot path.  This
+may be anything ranging from a boot using tboot or trustedgrub to just
+booting from a known-good device (like a USB drive or CD).
+
+When a dm-verity device is configured, it is expected that the caller
+has been authenticated in some way (cryptographic signatures, etc).
+After instantiation, all hashes will be verified on-demand during
+disk access.  If they cannot be verified up to the root node of the
+tree, the root hash, then the I/O will fail.  This should identify
+tampering with any data on the device and the hash data.
+
+Cryptographic hashes are used to assert the integrity of the device on a
+per-block basis.  This allows for a lightweight hash computation on first read
+into the page cache.  Block hashes are stored linearly-aligned to the nearest
+block the size of a page.
+
+Hash Tree
+---------
+
+Each node in the tree is a cryptographic hash.  If it is a leaf node, the hash
+is of some block data on disk.  If it is an intermediary node, then the hash is
+of a number of child nodes.
+
+Each entry in the tree is a collection of neighboring nodes that fit in one
+block.  The number is determined based on block_size and the size of the
+selected cryptographic digest algorithm.  The hashes are linearly-ordered in
+this entry and any unaligned trailing space is ignored but included when
+calculating the parent node.
+
+The tree looks something like:
+
+alg = sha256, num_blocks = 32768, block_size = 4096
+
+                                 [   root    ]
+                                /    . . .    \
+                     [entry_0]                 [entry_1]
+                    /  . . .  \                 . . .   \
+         [entry_0_0]   . . .  [entry_0_127]    . . . .  [entry_1_127]
+           / ... \             /   . . .  \             /           \
+     blk_0 ... blk_127  blk_16256   blk_16383      blk_32640 . . . blk_32767
+
+
+On-disk format
+==============
+
+Below is the recommended on-disk format. The verity kernel code does not
+read the on-disk header. It only reads the hash blocks which directly
+follow the header. It is expected that a user-space tool will verify the
+integrity of the verity_header and then call dmsetup with the correct
+parameters. Alternatively, the header can be omitted and the dmsetup
+parameters can be passed via the kernel command-line in a rooted chain
+of trust where the command-line is verified.
+
+The on-disk format is especially useful in cases where the hash blocks
+are on a separate partition. The magic number allows easy identification
+of the partition contents. Alternatively, the hash blocks can be stored
+in the same partition as the data to be verified. In such a configuration
+the filesystem on the partition would be sized a little smaller than
+the full-partition, leaving room for the hash blocks.
+
+struct superblock {
+	uint8_t signature[8]
+		"verity\0\0";
+
+	uint8_t version;
+		1 - current format
+
+	uint8_t data_block_bits;
+		log2(data block size)
+
+	uint8_t hash_block_bits;
+		log2(hash block size)
+
+	uint8_t pad1[1];
+		zero padding
+
+	uint16_t salt_size;
+		big-endian salt size
+
+	uint8_t pad2[2];
+		zero padding
+
+	uint32_t data_blocks_hi;
+		big-endian high 32 bits of the 64-bit number of data blocks
+
+	uint32_t data_blocks_lo;
+		big-endian low 32 bits of the 64-bit number of data blocks
+
+	uint8_t algorithm[16];
+		cryptographic algorithm
+
+	uint8_t salt[384];
+		salt (the salt size is specified above)
+
+	uint8_t pad3[88];
+		zero padding to 512-byte boundary
+}
+
+Directly following the header (and with sector number padded to the next hash
+block boundary) are the hash blocks which are stored a depth at a time
+(starting from the root), sorted in order of increasing index.
+
+Status
+======
+V (for Valid) is returned if every check performed so far was valid.
+If any check failed, C (for Corruption) is returned.
+
+Example
+=======
+
+Setup a device:
+  dmsetup create vroot --table \
+    "0 2097152 "\
+    "verity 1 /dev/sda1 /dev/sda2 4096 4096 2097152 1 "\
+    "4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076 "\
+    "1234000000000000000000000000000000000000000000000000000000000000"
+
+A command line tool veritysetup is available to compute or verify
+the hash tree or activate the kernel driver.  This is available from
+the LVM2 upstream repository and may be supplied as a package called
+device-mapper-verity-tools:
+    git://sources.redhat.com/git/lvm2
+    http://sourceware.org/git/?p=lvm2.git
+    http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/verity?cvsroot=lvm2
+
+veritysetup -a vroot /dev/sda1 /dev/sda2 \
+	4392712ba01368efdf14b05c76f9e4df0d53664630b5d48632ed17a137f39076