# Changelog

## v18.10: (Upcoming Release)

## v18.07:

### bdev

A new public header file bdev_module.h has been introduced to facilitate the
development of new bdev modules. This header includes an interface for the
spdk_bdev_part and spdk_bdev_part_base objects to enable the creation of
multiple virtual bdevs on top of a single base bdev and should act as the
primary API for module authors.

spdk_bdev_get_opts() and spdk_bdev_set_opts() were added to set bdev-wide
options.

A mechanism for handling out of memory condition errors (ENOMEM) returned from
I/O submission requests at the bdev layer has been added. See
spdk_bdev_queue_io_wait().

The spdk_bdev_get_io_stat() function now returns cumulative totals instead of
resetting on each call. This allows multiple callers to query I/O statistics
without conflicting with each other. Existing users will need to adjust their
code to record the previous I/O statistics to calculate the delta between calls.

I/O queue depth tracking and samples options have been added. See
spdk_bdev_get_qd(), spdk_bdev_get_qd_sampling_period(), and
spdk_bdev_set_qd_sampling_period().

### RAID module
A new bdev module called "raid" has been added as experimental module which
aggregates underlying NVMe bdevs and exposes a single raid bdev. Please note
that vhost will not work with this module because it does not yet have support
for multi-element io vectors.

### Log

The debug log component flag available on several SPDK applications has been
renamed from `-t` to `-L` to prevent confusion with tracepoints and to allow the
option to be added to tools that already use `-t` to mean something else.

### Blobstore

A new function, spdk_bs_dump(), has been added that dumps all of the contents of
a blobstore to a file pointer. This includes the metadata and is very useful for
debugging.

Two new operations have been added for thin-provisioned blobs.
spdk_bs_inflate_blob() will allocate clusters for all thinly provisioned regions
of the blob and populate them with the correct data by reading from the backing
blob(s). spdk_bs_blob_decouple_parent() works similarly, but will only allocate
clusters that correspond to data in the blob's immediate parent. Clusters
allocated to grandparents or that aren't allocated at all will remain
thin-provisioned.

### BlobFS

Changed the return type of spdk_file_truncate() from void to int to allow the
propagation of `ENOMEM` errors.

### NVMe Driver

The new API functions spdk_nvme_qpair_add_cmd_error_injection() and
spdk_nvme_qpair_remove_cmd_error_injection() have been added for NVMe error
emulation. Users can set a specified command to fail with a particular error
status.

Changed the name `timeout_sec` parameter to `timeout_us` in
spdk_nvme_ctrlr_register_timeout_callback(), and also changed the type from
uint32_t to uint64_t. This will give users more fine-grained control over the
timeout period.

Basic support for Open Channel SSDs was added. See nvme_ocssd.h

### NVMe Over Fabrics

The spdk_nvmf_tgt_destroy() function is now asynchronous and takes a callback
as a parameter.

spdk_nvmf_qpair_disconnect() was added to allow the user to disconnect qpairs.

spdk_nvmf_subsystem_get_max_namespaces() was added to query the maximum allowed
number of namespaces for a given subsystem.

### Build System

The build system now generates a combined shared library (libspdk.so) that may
be used in place of the individual static libraries (libspdk_*.a). The combined
library includes all components of SPDK and is intended to make linking against
SPDK easier. The static libraries are also still provided for users that prefer
to link only the minimal set of components required.

### git pre-commit and pre-push hooks

The pre-commit hook will run `scripts/check_format.sh` and verify there are no
formating errors before allowing `git commit` to run. The pre-push hook runs
`make CONFIG_WERROR=y` with and without `CONFIG_DEBUG=y` using both the gcc and
clang compiler before allowing `git push` to run. Following each DEBUG build
`test/unit/unittest.sh` is run and verified. Results are recorded in the
`make.log` file.

To enable type: 'git config core.hooksPath .githooks'. To override after
configuration use the `git --no-verify` flag.

### RPC

The `start_nbd_disk` RPC method now returns the path to the kernel NBD device node
rather than always returning `true`.

### DPDK 18.05

The DPDK submodule has been rebased on the DPDK 18.05 release.  DPDK 18.05 supports
dynamic memory allocation, but due to some issues found after the DPDK 18.05 release,
that support is not enabled for SPDK 18.07.  Therefore, SPDK 18.07 will continue to use
the legacy memory allocation model.  The plan is to enable dynamic memory allocation
after the DPDK 18.08 release which should fix these issues.

### Environment Abstraction Layer and Event Framework

The spdk_mem_map_translate() function now takes a size parameter to indicate the size of
the memory region.  This can be used by environment implementations to validate the
requested translation.

The I/O Channel implementation has been moved to its own library - lib/thread. The
public API that was previously in spdk/io_channel.h is now in spdk/thread.h The
file spdk/io_channel.h remains and includes spdk/thread.h.

spdk_reactor_get_tsc_stats was added to return interesting statistics for each
reactor.

### IOAT

IOAT for copy engine is disabled by default. It can be enabled by specifying the Enable
option with "Yes" in `[Ioat]` section of the configuration file. The Disable option is
now deprecated and will be removed in a future release.

## v18.04: Logical Volume Snapshot/Clone, iSCSI Initiator, Bdev QoS, VPP Userspace TCP/IP

### vhost

The SPDK vhost-scsi, vhost-blk and vhost-nvme applications have fixes to address the
DPDK rte_vhost vulnerability [CVE-2018-1059](http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-1059).
Please see this [security advisory](https://access.redhat.com/security/cve/cve-2018-1059)
for additional information on the DPDK vulnerability.

Workarounds have been added to ensure vhost compatibility with QEMU 2.12.

EXPERIMENTAL: Support for vhost-nvme has been added to the SPDK vhost target. See the
[vhost documentation](http://www.spdk.io/doc/vhost.html) for more details.

### Unified Target Application

A new unified SPDK target application, `spdk_tgt`, has been added. This application combines the
functionality of several existing SPDK applications, including the iSCSI target, NVMe-oF target,
and vhost target. The new application can be managed through the existing configuration file and
[JSON-RPC](http://www.spdk.io/doc/jsonrpc.html) methods.

### Env

spdk_mempool_get_bulk() has been added to wrap DPDK rte_mempool_get_bulk().

New memory management functions spdk_malloc(), spdk_zmalloc(), and spdk_free() have been added.
These new functions have a `flags` parameter that allows the user to specify whether the allocated
memory needs to be suitable for DMA and whether it should be shared across processes with the same
shm_id. The new functions are intended to replace spdk_dma_malloc() and related functions, which will
eventually be deprecated and removed.

### Bdev

A new optional bdev module interface function, `init_complete`, has been added to notify bdev modules
when the bdev subsystem initialization is complete. This may be useful for virtual bdevs that require
notification that the set of initialization examine() calls is complete.

The bdev layer now allows modules to provide an optional per-bdev UUID, which can be retrieved with
the spdk_bdev_get_uuid() function.

Enforcement of IOPS limits for quality of service (QoS) has been added to the bdev layer. See the
[set_bdev_qos_limit_iops](http://www.spdk.io/doc/jsonrpc.html#rpc_set_bdev_qos_limit_iops) documentation
for more details.

### RPC

The `[Rpc]` configuration file section, which was deprecated in v18.01, has been removed.
Users should switch to the `-r` command-line parameter instead.

The JSON-RPC server implementation now allows up to 32 megabyte responses, growing as
needed; previously, the response was limited to 32 kilobytes.

### SPDKCLI

EXPERIMENTAL: New SPDKCLI interactive command tool for managing SPDK is available.
See the [SPDKCLI](http://www.spdk.io/doc/spdkcli.html) documentation for more details.

### NVMe Driver

EXPERIMENTAL: Support for WDS and RDS capable CMBs in NVMe controllers has been added. This support is
experimental pending a functional allocator to free and reallocate CMB buffers.

spdk_nvme_ns_get_uuid() has been added to allow retrieval of per-namespace UUIDs when available.

New API functions spdk_nvme_ctrlr_get_first_active_ns() and spdk_nvme_ctrlr_get_next_active_ns()
have been added to iterate active namespaces, as well as spdk_nvme_ctrlr_is_active_ns() to check if
a namespace ID is active.

### NVMe-oF Target

Namespaces may now be assigned unique identifiers via new optional `eui64` and `nguid` parameters
to the `nvmf_subsystem_add_ns` RPC method. Additionally, the NVMe-oF target automatically exposes
the backing bdev's UUID as the namespace UUID when available.

spdk_nvmf_subsystem_remove_ns() is now asynchronous and requires a callback to indicate completion.

### Blobstore

A number of functions have been renamed:

- spdk_bs_io_write_blob() => spdk_blob_io_write()
- spdk_bs_io_read_blob() => spdk_blob_io_read()
- spdk_bs_io_writev_blob() => spdk_blob_io_writev()
- spdk_bs_io_readv_blob() => spdk_blob_io_readv()
- spdk_bs_io_unmap_blob() => spdk_blob_io_unmap()
- spdk_bs_io_write_zeroes_blob() => spdk_blob_io_write_zeroes()

The old names still exist but are deprecated.  They will be removed in the v18.07 release.

spdk_blob_resize() is now an asynchronous operation to enable resizing a blob while I/O
are in progress to that blob on other threads.  An explicit spdk_blob_sync_md() is still
required to sync the updated metadata to disk.

### Logical Volumes

A new `destroy_lvol_bdev` RPC method to delete logical volumes has been added.

Lvols now have their own UUIDs which replace previous LvolStoreUUID_BlobID combination.

New Snapshot and Clone funtionalities have been added. User may create Snapshots of existing Lvols
and Clones of existing Snapshots.
See the [lvol snapshots](http://www.spdk.io/doc/logical_volumes.html#lvol_snapshots) documentation
for more details.

Resizing logical volumes is now supported via the `resize_lvol_bdev` RPC method.

### Lib

A set of changes were made in the SPDK's lib code altering
instances of calls to `exit()` and `abort()` to return a failure instead
wherever reasonably possible.

spdk_app_start() no longer exit()'s on an internal failure, but
instead returns a non-zero error status.

spdk_app_parse_args() no longer exit()'s on help, '-h', or an invalid
option, but instead returns SPDK_APP_PARSE_ARGS_HELP and
SPDK_APP_PARSE_ARGS_FAIL, respectively, and SPDK_APP_PARSE_ARGS_SUCCESS
on success.

spdk_pci_get_device() has been deprecated and will be removed in SPDK v18.07.

### I/O Channels

The prototype for spdk_poller_fn() has been modified; it now returns a value indicating
whether or not the poller did any work.  Existing pollers will need to be updated to
return a value.

### iSCSI Target

The SPDK iSCSI target now supports the fd.io Vector Packet Processing (VPP) framework userspace
TCP/IP stack. See the [iSCSI VPP documentation](http://www.spdk.io/doc/iscsi.html#vpp) for more
details.

### iSCSI initiator

An iSCSI initiator bdev module has been added to SPDK.  This module should be considered
experimental pending additional features and tests.  More details can be found in
lib/bdev/iscsi/README.

### PMDK

The persistent memory (PMDK) bdev module is now enabled using `--with-pmdk` instead of
`--with-nvml`.  This reflects the renaming of the persistent memory library from NVML to
PMDK.

### Virtio Block driver

A userspace driver for Virtio Block devices has been added. It was built on top of the
[Virtio](http://www.spdk.io/doc/virtio.html) library and can be managed similarly to
the Virtio SCSI driver. See the
[Virtio Block](http://www.spdk.io/doc/bdev.html#bdev_config_virtio_blk) reference for
more information.

### Virtio with 2MB hugepages

The previous 1GB hugepage limitation has now been lifted. A new `-g` command-line option
enables SPDK Virtio to work with 2MB hugepages.
See [2MB hugepages](http://www.spdk.io/doc/virtio.html#virtio_2mb) for details.

## v18.01: Blobstore Thin Provisioning

### Build System

The build system now includes a `make install` rule, including support for the common
`DESTDIR` and `prefix` variables as used in other build systems.  Additionally, the prefix
may be set via the configure `--prefix` option.  Example: `make install prefix=/usr`.

### RPC

A JSON RPC listener is now enabled by default using a UNIX domain socket at /var/run/spdk.sock.
A -r option command line option has been added to enable an alternative UNIX domain socket location,
or a TCP port in the format ip_addr:tcp_port (i.e. 127.0.0.1:5260).  The Rpc configuration file
section is now deprecated and will be removed in the v18.04 release.

### I/O Channels

spdk_poller_register() and spdk_poller_unregister() were moved from the event
framework (include/spdk/event.h) to the I/O channel library
(include/spdk/io_channel.h). This allows code that doesn't depend on the event
framework to request registration and unregistration of pollers.

spdk_for_each_channel() now allows asynchronous operations during iteration.
Instead of immediately continuing the interation upon returning from the iteration
callback, the user must call spdk_for_each_channel_continue() to resume iteration.

### Block Device Abstraction Layer (bdev)

The poller abstraction was removed from the bdev layer. There is now a general purpose
abstraction for pollers available in include/spdk/io_channel.h

### Lib

A set of changes were made in the SPDK's lib code altering,
instances of calls to `exit()` and `abort()` to return a failure instead
wherever reasonably possible.  This has resulted in return type changes of
the API for:

- spdk_env_init() from type `void` to `int`.
- spdk_mem_map_init() from type `void` to `int`.

Applications making use of these APIs should be modified to check for
a non-zero return value instead of relying on them to fail without return.

### NVMe Driver

SPDK now supports hotplug for vfio-attached devices. But there is one thing keep in mind:
Only physical removal events are supported; removing devices via the sysfs `remove` file will not work.

### NVMe-oF Target

Subsystems are no longer tied explicitly to CPU cores. Instead, connections are handed out to the available
cores round-robin. The "Core" option in the configuration file has been removed.

### Blobstore

A number of functions have been renamed:

- spdk_bs_md_resize_blob() => spdk_blob_resize()
- spdk_bs_md_sync_blob() => spdk_blob_sync_md()
- spdk_bs_md_close_blob() => spdk_blob_close()
- spdk_bs_md_get_xattr_names() => spdk_blob_get_xattr_names()
- spdk_bs_md_get_xattr_value() => spdk_blob_get_xattr_value()
- spdk_blob_md_set_xattr() => spdk_blob_set_xattr()
- spdk_blob_md_remove_xattr() => spdk_blob_remove_xattr()
- spdk_bs_md_create_blob() => spdk_bs_create_blob()
- spdk_bs_md_open_blob() => spdk_bs_open_blob()
- spdk_bs_md_delete_blob() => spdk_bs_delete_blob()
- spdk_bs_md_iter_first() => spdk_bs_iter_first()
- spdk_bs_md_iter_next() => spdk_bs_iter_next()

The function signature of spdk_blob_close() has changed.  It now takes a struct spdk_blob * argument
rather than struct spdk_blob **.

The function signature of spdk_bs_iter_next() has changed.  It now takes a struct spdk_blob * argument
rather than struct spdk_blob **.

Thin provisioning support has been added to the blobstore.  It can be enabled by setting the
`thin_provision` flag in struct spdk_blob_opts when calling spdk_bs_create_blob_ext().

### NBD device

The NBD application (test/lib/bdev/nbd) has been removed; Same functionality can now be
achieved by using the test/app/bdev_svc application and start_nbd_disk RPC method.
See the [GPT](http://www.spdk.io/doc/bdev.html#bdev_config_gpt) documentation for more details.

### FIO plugin

SPDK `fio_plugin` now suports FIO 3.3. The support for previous FIO 2.21 has been dropped,
although it still remains to work for now. The new FIO contains huge amount of bugfixes and
it's recommended to do an update.

### Virtio library

Previously a part of the bdev_virtio module, now a separate library. Virtio is now available
via `spdk_internal/virtio.h` file. This is an internal interface to be used when implementing
new Virtio backends, namely Virtio-BLK.

### iSCSI

The MinConnectionIdleInterval parameter has been removed, and connections are no longer migrated
to an epoll/kqueue descriptor on the master core when idle.

## v17.10: Logical Volumes

### New dependencies

libuuid was added as new dependency for logical volumes.

libnuma is now required unconditionally now that the DPDK submodule has been updated to DPDK 17.08.

### Block Device Abstraction Layer (bdev)

An [fio](http://github.com/axboe/fio) plugin was added that can route
I/O to the bdev layer. See the [plugin documentation](https://github.com/spdk/spdk/tree/master/examples/bdev/fio_plugin/)
for more information.

spdk_bdev_unmap() was modified to take an offset and a length in bytes as
arguments instead of requiring the user to provide an array of SCSI
unmap descriptors. This limits unmaps to a single contiguous range.

spdk_bdev_write_zeroes() was introduced.  It ensures that all specified blocks will be zeroed out.
If a block device doesn't natively support a write zeroes command, the bdev layer emulates it using
write commands.

New API functions that accept I/O parameters in units of blocks instead of bytes
have been added:
- spdk_bdev_read_blocks(), spdk_bdev_readv_blocks()
- spdk_bdev_write_blocks(), spdk_bdev_writev_blocks()
- spdk_bdev_write_zeroes_blocks()
- spdk_bdev_unmap_blocks()

The bdev layer now handles temporary out-of-memory I/O failures internally by queueing the I/O to be
retried later.

### Linux AIO bdev

The AIO bdev now allows the user to override the auto-detected block size.

### NVMe driver

The NVMe driver now recognizes the NVMe 1.3 Namespace Optimal I/O Boundary field.
NVMe 1.3 devices may report an optimal I/O boundary, which the driver will take
into account when splitting I/O requests.

The HotplugEnable option in `[Nvme]` sections of the configuration file is now
"No" by default. It was previously "Yes".

The NVMe library now includes a spdk_nvme_ns_get_ctrlr() function which returns the
NVMe Controller associated with a given namespace.

The NVMe library now allows the user to specify a host identifier when attaching
to a controller.  The host identifier is used as part of the Reservations feature,
as well as in the NVMe-oF Connect command.  The default host ID is also now a
randomly-generated UUID, and the default host NQN uses the host ID to generate
a UUID-based NQN.

spdk_nvme_connect() was added to allow the user to connect directly to a single
NVMe or NVMe-oF controller.

### NVMe-oF Target (nvmf_tgt)

The NVMe-oF target no longer requires any in-capsule data buffers to run, and
the feature is now entirely optional. Previously, at least 4 KiB in-capsule
data buffers were required.

NVMe-oF subsytems have a new configuration option, AllowAnyHost, to control
whether the host NQN whitelist is enforced when accepting new connections.
If no Host options have been specified and AllowAnyHost is disabled, the
connection will be denied; this is a behavior change from previous releases,
which allowed any host NQN to connect if the Host list was empty.
AllowAnyHost is disabled by default.

NVMe-oF namespaces may now be assigned arbitrary namespace IDs, and the number
of namespaces per subsystem is no longer limited.

The NVMe-oF target now supports the Write Zeroes command.

### Environment Abstraction Layer

A new default value, SPDK_MEMPOOL_DEFAULT_CACHE_SIZE, was added to provide
additional clarity when constructing spdk_mempools. Previously, -1 could be
passed and the library would choose a reasonable default, but this new value
makes it explicit that the default is being used.

### Blobstore

The blobstore super block now contains a bstype field to identify the type of the blobstore.
Existing code should be updated to fill out bstype when calling spdk_bs_init() and spdk_bs_load().

spdk_bs_destroy() was added to allow destroying blobstore on device
with an initialized blobstore.

spdk_bs_io_readv_blob() and spdk_bs_io_writev_blob() were added to enable
scattered payloads.

A CLI tool for blobstore has been added, allowing basic operations through either command
line or shell interface.  See the [blobcli](https://github.com/spdk/spdk/tree/master/examples/blob/cli)
documentation for more details.

### Event Framework

The ability to set a thread name, previously only used by the reactor code, is
now part of the spdk_thread_allocate() API.  Users may specify a thread name
which will show up in tools like `gdb`.

### Log

The spdk_trace_dump() function now takes a new parameter to allow the caller to
specify an output file handle (stdout or stderr, for example).

### Logical Volumes

Logical volumes library built on top of SPDK blobstore has been added.
It is possible to create logical volumes on top of other devices using RPC.

See the [logical volumes](http://www.spdk.io/doc/logical_volumes.html) documentation for more information.

### Persistent Memory

A new persistent memory bdev type has been added.
The persistent memory block device is built on top of [libpmemblk](http://pmem.io/nvml/libpmemblk/).
It is possible to create pmem devices on top of pmem pool files using RPC.

See the [Pmem Block Device](http://www.spdk.io/doc/bdev.html#bdev_config_pmem) documentation for more information.

### Virtio SCSI driver

A userspace driver for Virtio SCSI devices has been added.
The driver is capable of creating block devices on top of LUNs exposed by another SPDK vhost-scsi application.

See the [Virtio SCSI](http://www.spdk.io/doc/virtio.html) documentation and [Getting Started](http://www.spdk.io/doc/bdev.html#bdev_config_virtio_scsi) guide for more information.

### Vhost target

The vhost target application now supports live migration between QEMU instances.


## v17.07: Build system improvements, userspace vhost-blk target, and GPT bdev

### Build System

A `configure` script has been added to simplify the build configuration process.
The existing CONFIG file and `make CONFIG_...` options are also still supported.
Run `./configure --help` for information about available configuration options.

A DPDK submodule has been added to make building SPDK easier.  If no `--with-dpdk`
option is specified to configure, the SPDK build system will automatically build a
known-good configuration of DPDK with the minimal options enabled.  See the Building
section of README.md for more information.

A [Vagrant](https://www.vagrantup.com/) setup has been added to make it easier to
develop and use SPDK on systems without suitable NVMe hardware.  See the Vagrant
section of README.md for more information.

### Userspace vhost-blk target

The vhost library and example app have been updated to support the vhost-blk
protocol in addition to the existing vhost-scsi protocol.
See the [vhost documentation](http://www.spdk.io/doc/vhost.html) for more details.

### Block device abstraction layer (bdev)

A GPT virtual block device has been added, which automatically exposes GPT partitions
with a special SPDK-specific partition type as bdevs.
See the [GPT bdev documentation](http://www.spdk.io/doc/bdev.md#bdev_config_gpt) for
more information.

### NVMe driver

The NVMe driver has been updated to support recent Intel SSDs, including the Intel®
Optane™ SSD DC P4800X series.

A workaround has been added for devices that failed to recognize register writes
during controller reset.

The NVMe driver now allocates request tracking objects on a per-queue basis.  The
number of requests allowed on an I/O queue may be set during `spdk_nvme_probe()` by
modifying `io_queue_requests` in the opts structure.

The SPDK NVMe `fio_plugin` has been updated to support multiple threads (`numjobs`).

spdk_nvme_ctrlr_alloc_io_qpair() has been modified to allow the user to override
controller-level options for each individual I/O queue pair.
Existing callers with qprio == 0 can be updated to:
~~~
... = spdk_nvme_ctrlr_alloc_io_qpair(ctrlr, NULL, 0);
~~~
Callers that need to specify a non-default qprio should be updated to:
~~~
struct spdk_nvme_io_qpair_opts opts;
spdk_nvme_ctrlr_get_default_io_qpair_opts(ctrlr, &opts, sizeof(opts));
opts.qprio = SPDK_NVME_QPRIO_...;
... = spdk_nvme_ctrlr_alloc_io_qpair(ctrlr, &opts, sizeof(opts));
~~~

### Environment Abstraction Layer

The environment abstraction layer has been updated to include several new functions
in order to wrap additional DPDK functionality. See `include/spdk/env.h` for the
current set of functions.

### SPDK Performance Analysis with Intel® VTune™ Amplifier

Support for SPDK performance analysis has been added to Intel® VTune™ Amplifier 2018.

This analysis provides:
- I/O performance monitoring (calculating standard I/O metrics like IOPS, throughput, etc.)
- Tuning insights on the interplay of I/O and compute devices by estimating how many cores
  would be reasonable to provide for SPDK to keep up with a current storage workload.

See the VTune Amplifier documentation for more information.


## v17.03: Blobstore and userspace vhost-scsi target

### Blobstore and BlobFS

The blobstore is a persistent, power-fail safe block allocator designed to be
used as the local storage system backing a higher-level storage service.
See the [blobstore documentation](http://www.spdk.io/doc/blob.html) for more details.

BlobFS adds basic filesystem functionality like filenames on top of the blobstore.
This release also includes a RocksDB Env implementation using BlobFS in place of the
kernel filesystem.
See the [BlobFS documentation](http://www.spdk.io/doc/blobfs.html) for more details.

### Userspace vhost-scsi target

A userspace implementation of the QEMU vhost-scsi protocol has been added.
The vhost target is capable of exporting SPDK bdevs to QEMU-based VMs as virtio devices.
See the [vhost documentation](http://www.spdk.io/doc/vhost.html) for more details.

### Event framework

The overhead of the main reactor event loop was reduced by optimizing the number of
calls to spdk_get_ticks() per iteration.

### NVMe library

The NVMe library will now automatically split readv/writev requests with scatter-gather
lists that do not map to valid PRP lists when the NVMe controller does not natively
support SGLs.

The `identify` and `perf` NVMe examples were modified to add a consistent format for
specifying remote NVMe over Fabrics devices via the `-r` option.
This is implemented using the new `spdk_nvme_transport_id_parse()` function.

### iSCSI Target

The [Nvme] section of the configuration file was modified to remove the `BDF` directive
and replace it with a `TransportID` directive. Both local (PCIe) and remote (NVMe-oF)
devices can now be specified as the backing block device. A script to generate an
entire [Nvme] section based on the local NVMe devices attached was added at
`scripts/gen_nvme.sh`.

### NVMe-oF Target

The [Nvme] section of the configuration file was modified to remove the `BDF` directive
and replace it with a `TransportID` directive. Both local (PCIe) and remote (NVMe-oF)
devices can now be specified as the backing block device. A script to generate an
entire [Nvme] section based on the local NVMe devices attached was added at
`scripts/gen_nvme.sh`.

## v16.12: NVMe over Fabrics host, hotplug, and multi-process

### NVMe library

The NVMe library has been changed to create its own request memory pool rather than
requiring the user to initialize the global `request_mempool` variable.  Apps can be
updated by simply removing the initialization of `request_mempool`.  Since the NVMe
library user no longer needs to know the size of the internal NVMe request
structure to create the pool, the `spdk_nvme_request_size()` function was also removed.

The `spdk_nvme_ns_cmd_deallocate()` function was renamed and extended to become
`spdk_nvme_ns_cmd_dataset_management()`, which allows access to all of the NVMe
Dataset Management command's parameters.  Existing callers can be updated to use
`spdk_nvme_ns_cmd_dataset_management()` with `SPDK_NVME_DSM_ATTR_DEALLOCATE` as the
`type` parameter.

The NVMe library SGL callback prototype has been changed to return virtual addresses
rather than physical addresses.  Callers of `spdk_nvme_ns_cmd_readv()` and
`spdk_nvme_ns_cmd_writev()` must update their `next_sge_fn` callbacks to match.

The NVMe library now supports NVMe over Fabrics devices in addition to the existing
support for local PCIe-attached NVMe devices.  For an example of how to enable
NVMe over Fabrics support in an application, see `examples/nvme/identify` and
`examples/nvme/perf`.

Hot insert/remove support for NVMe devices has been added.  To enable NVMe hotplug
support, an application should call the `spdk_nvme_probe()` function on a regular
basis to probe for new devices (reported via the existing `probe_cb` callback) and
removed devices (reported via a new `remove_cb` callback).  Hotplug is currently
only supported on Linux with the `uio_pci_generic` driver, and newly-added NVMe
devices must be bound to `uio_pci_generic` by an external script or tool.

Multiple processes may now coordinate and use a single NVMe device simultaneously
using [DPDK Multi-process Support](http://dpdk.org/doc/guides/prog_guide/multi_proc_support.html).

### NVMe over Fabrics target (`nvmf_tgt`)

The `nvmf_tgt` configuration file format has been updated significantly to enable
new features.  See the example configuration file `etc/spdk/nvmf.conf.in` for
more details on the new and changed options.

The NVMe over Fabrics target now supports virtual mode subsystems, which allow the
user to export devices from the SPDK block device abstraction layer as NVMe over
Fabrics subsystems.  Direct mode (raw NVMe device access) is also still supported,
and a single `nvmf_tgt` may export both types of subsystems simultaneously.

### Block device abstraction layer (bdev)

The bdev layer now supports scatter/gather read and write I/O APIs, and the NVMe
blockdev driver has been updated to support scatter/gather.  Apps can use the
new scatter/gather support via the `spdk_bdev_readv()` and `spdk_bdev_writev()`
functions.

The bdev status returned from each I/O has been extended to pass through NVMe
or SCSI status codes directly in cases where the underlying device can provide
a more specific status code.

A Ceph RBD (RADOS Block Device) blockdev driver has been added.  This allows the
`iscsi_tgt` and `nvmf_tgt` apps to export Ceph RBD volumes as iSCSI LUNs or
NVMe namespaces.

### General changes

`libpciaccess` has been removed as a dependency and DPDK PCI enumeration is
used instead. Prior to DPDK 16.07 enumeration by class code was not supported,
so for earlier DPDK versions, only Intel SSD DC P3x00 devices will be discovered
by the NVMe library.

The `env` environment abstraction library has been introduced, and a default
DPDK-based implementation is provided as part of SPDK.  The goal of the `env`
layer is to enable use of alternate user-mode memory allocation and PCI access
libraries.  See `doc/porting.md` for more details.

The build process has been modified to produce all of the library files in the
`build/lib` directory.  This is intended to simplify the use of SPDK from external
projects, which can now link to SPDK libraries by adding the `build/lib` directory
to the library path via `-L` and linking the SPDK libraries by name (for example,
`-lspdk_nvme -lspdk_log -lspdk_util`).

`nvmf_tgt` and `iscsi_tgt` now have a JSON-RPC interface, which allows the user
to query and modify the configuration at runtime.  The RPC service is disabled by
default, since it currently does not provide any authentication or security
mechanisms; it should only be enabled on systems with controlled user access
behind a firewall. An example RPC client implemented in Python is provided in
`scripts/rpc.py`.

## v16.08: iSCSI target, NVMe over Fabrics maturity

This release adds a userspace iSCSI target. The iSCSI target is capable of exporting
NVMe devices over a network using the iSCSI protocol. The application is located
in app/iscsi_tgt and a documented configuration file can be found at etc/spdk/spdk.conf.in.

This release also significantly improves the existing NVMe over Fabrics target.
  - The configuration file format was changed, which will require updates to
    any existing nvmf.conf files (see `etc/spdk/nvmf.conf.in`):
    - `SubsystemGroup` was renamed to `Subsystem`.
    - `AuthFile` was removed (it was unimplemented).
    - `nvmf_tgt` was updated to correctly recognize NQN (NVMe Qualified Names)
      when naming subsystems.  The default node name was changed to reflect this;
      it is now "nqn.2016-06.io.spdk".
    - `Port` and `Host` sections were merged into the `Subsystem` section
    - Global options to control max queue depth, number of queues, max I/O
      size, and max in-capsule data size were added.
    - The Nvme section was removed. Now a list of devices is specified by
      bus/device/function directly in the Subsystem section.
    - Subsystems now have a Mode, which can be Direct or Virtual. This is an attempt
      to future-proof the interface, so the only mode supported by this release
      is "Direct".
  - Many bug fixes and cleanups were applied to the `nvmf_tgt` app and library.
  - The target now supports discovery.

This release also adds one new feature and provides some better examples and tools
for the NVMe driver.
  - The Weighted Round Robin arbitration method is now supported. This allows
    the user to specify different priorities on a per-I/O-queue basis.  To
    enable WRR, set the `arb_mechanism` field during `spdk_nvme_probe()`.
  - A simplified "Hello World" example was added to show the proper way to use
    the NVMe library API; see `examples/nvme/hello_world/hello_world.c`.
  - A test for measuring software overhead was added. See `test/lib/nvme/overhead`.

## v16.06: NVMf userspace target

This release adds a userspace NVMf (NVMe over Fabrics) target, conforming to the
newly-released NVMf 1.0/NVMe 1.2.1 specification.  The NVMf target exports NVMe
devices from a host machine over the network via RDMA.  Currently, the target is
limited to directly exporting physical NVMe devices, and the discovery subsystem
is not supported.

This release includes a general API cleanup, including renaming all declarations
in public headers to include a `spdk` prefix to prevent namespace clashes with
user code.

- NVMe
  - The `nvme_attach()` API was reworked into a new probe/attach model, which
  moves device detection into the NVMe library.  The new API also allows
  parallel initialization of NVMe controllers, providing a major reduction in
  startup time when using multiple controllers.
  - I/O queue allocation was changed to be explicit in the API.  Each function
  that generates I/O requests now takes a queue pair (`spdk_nvme_qpair *`)
  argument, and I/O queues may be allocated using
  `spdk_nvme_ctrlr_alloc_io_qpair()`.  This allows more flexible assignment of
  queue pairs than the previous model, which only allowed a single queue
  per thread and limited the total number of I/O queues to the lowest number
  supported on any attached controller.
  - Added support for the Write Zeroes command.
  - `examples/nvme/perf` can now report I/O command latency from the
   the controller's viewpoint using the Intel vendor-specific read/write latency
   log page.
  - Added namespace reservation command support, which can be used to coordinate
  sharing of a namespace between multiple hosts.
  - Added hardware SGL support, which enables use of scattered buffers that
   don't conform to the PRP list alignment and length requirements on supported
   NVMe controllers.
  - Added end-to-end data protection support, including the ability to write and
  read metadata in extended LBA (metadata appended to each block of data in the
  buffer) and separate metadata buffer modes.
  See `spdk_nvme_ns_cmd_write_with_md()` and `spdk_nvme_ns_cmd_read_with_md()`
  for details.
- IOAT
  - The DMA block fill feature is now exposed via the `ioat_submit_fill()`
  function.  This is functionally similar to `memset()`, except the memory is
  filled with an 8-byte repeating pattern instead of a single byte like memset.
- PCI
  - Added support for using DPDK for PCI device mapping in addition to the
  existing libpciaccess option.  Using the DPDK PCI support also allows use of
  the Linux VFIO driver model, which means that SPDK userspace drivers will work
  with the IOMMU enabled.  Additionally, SPDK applications may be run as an
  unprivileged user with access restricted to a specific set of PCIe devices.
  - The PCI library API was made more generic to abstract away differences
  between the underlying PCI access implementations.

## v1.2.0: IOAT user-space driver

This release adds a user-space driver with support for the Intel I/O Acceleration Technology (I/OAT, also known as "Crystal Beach") DMA offload engine.

- IOAT
  - New user-space driver supporting DMA memory copy offload
  - Example programs `ioat/perf` and `ioat/verify`
  - Kernel-mode DMA engine test driver `kperf` for performance comparison
- NVMe
  - Per-I/O flags for Force Unit Access (FUA) and Limited Retry
  - Public API for retrieving log pages
  - Reservation register/acquire/release/report command support
  - Scattered payload support - an alternate API to provide I/O buffers via a sequence of callbacks
  - Declarations and `nvme/identify` support for Intel SSD DC P3700 series vendor-specific log pages and features
- Updated to support DPDK 2.2.0


## v1.0.0: NVMe user-space driver

This is the initial open source release of the Storage Performance Development Kit (SPDK).

Features:
- NVMe user-space driver
- NVMe example programs
  - `examples/nvme/perf` tests performance (IOPS) using the NVMe user-space driver
  - `examples/nvme/identify` displays NVMe controller information in a human-readable format
- Linux and FreeBSD support
