nvme

Added asynchronous probe support. New APIs spdk_nvme_probe_async(),
spdk_nvme_connect_async() and spdk_nvme_probe_poll_async() were added to enable
this feature. spdk_nvme_probe_async() and spdk_nvme_connect_async() return a
context associated with the specified controllers. Users then call
spdk_nvme_probe_poll_async() until it returns 0, indicating that the operation
completed.

A new qpair creation option, delay_pcie_doorbell, was added. This can be passed
to spdk_nvme_alloc_io_qpair(). This makes the I/O submission functions, such as
spdk_nvme_ns_writev(), skip ringing the submission queue doorbell. Instead the
doorbell will be rung as necessary inside spdk_nvme_qpair_process_completions().
This can result in significantly fewer MMIO writes to the doorbell register
under heavy load, greatly improving performance.

spdk_nvme_ctrlr_get_regs_cmbsz() was added to report the size of the controller
memory buffer, if available.

spdk_nvme_ctrlr_get_flags() was added to return controller feature
flags. Two flags are currently tracked:
SPDK_NVME_CTRLR_SGL_SUPPORTED
SPDK_NVME_CTRLR_SECURITY_SEND_RECV_SUPPORTED

The NVMe hotplug poller is now able to detach devices hot-removed from the system
via /sys/bus/pci/devices/<bdf>/remove and /sys/bus/pci/devices/<bdf>/driver/unbind.

Opal support was added for scan, take ownership, revert TPer, and dumping device
info. The nvme_manage tool can be used to perform these operations. The public
API functions are spdk_nvme_ctrlr_security_receive() and
spdk_nvme_ctrlr_security_send(). This module should be considered experimental
pending additional features and tests.

raid

Added new strip_size_kb rpc param on create to replace the more ambiguous
strip_size. The strip_size rpc param is deprecated.

thread

Added spdk_thread_has_pollers() function to verify if there are any registered
pollers to be run on the thread. Added spdk_thread_is_idle() function to check
if there are any scheduled operations to be performed on the thread at given
time.

spdk_thread_create() now takes an optional CPU affinity mask that is passed to
the scheduler.

spdk_thread_lib_init() now takes an optional context size. For each thread
created, an additional region of memory of this size will be allocated. A
pointer to this region of memory can be obtained by calling
spdk_thread_get_ctx(). The inverse operation is also available via
spdk_thread_get_from_ctx().

spdk_thread_poll() now optionally accepts the current time, in ticks. This can
be used to avoid some calls to spdk_get_ticks() internally.

spdk_app_start() now only accepts a single context argument.

bdev

An new API spdk_bdev_get_data_block_size has been added to get size of data
block except for metadata.

spdk_vbdev_register() has been deprecated. spdk_bdev_register() should be used
instead.

A mechanism for acquiring and releasing data buffers from bdev modules, used
to perform zero copy operations, was added.

New APIs spdk_bdev_get_md_size(), spdk_bdev_is_md_interleaved(), spdk_bdev_get_dif_type(),
spdk_bdev_is_dif_head_of_md(), and spdk_bdev_is_dif_check_enabled() have been
added to get metadata and DIF settings.

Bdevs claimed by the examine_config callback will be now further examined in the
examine_disk callback.

spdk_bdev_io_get_io_channel() was added as a convenient way to get an io_channel
from a bdev_io.

NVMe-oF Target

Support for per-device shared receive queues in the RDMA transport has been added.
It is enabled by default for any device that supports it.

The size of a shared receive queue is defined by transport configuration file parameter
MaxSRQDepth and nvmf_create_transport RPC method parameter max_srq_depth.
Default size is 4096.

Add model number as parameter to construct_nvmf_subsystem (-d option),
rather than using hardcoded define.

DIF passthrough feature has been added. DIF setting of the allocated bdevs is
exposed to the NVMe-oF initiator and data with DIF from the NVMe-oF initiator is
passed through to the allocated bdevs.

env

The phys_addr parameter in spdk_malloc() and spdk_zmalloc() has been deprecated.
For retrieving physical addresses, spdk_vtophys() should be used instead.

spdk_realloc() has been added to reallocate DMA/shared memory.

spdk_pci_device_is_removed() has been added to let the upper-layer SPDK drivers know
that device has a pending external hotremove request.

spdk_env_fini() and spdk_env_dpdk_post_fini() were added to release any resources
allocated by spdk_env_init() or spdk_env_dpdk_post_init() respectively. It is expected
that common usage of those functions is to call them just before terminating the process.

Added spdk_iommu_is_enabled() to report if SPDK application is using IOMMU for DMA.

DPDK

Dropped support for DPDK 17.07 and earlier, which SPDK won't even compile with right now.

Updated DPDK submodule to DPDK 19.02.

rpc

New get_spdk_version RPC method is introduced to get version info of the running SPDK application.

The start_nbd_disk RPC method now take nbd_device as an optional parameter. If nbd_device
is specified, use that specified nbd device. If it's not specified, pick available one.

iSCSI target

DIF strip and insert is now supported. DIF settings are not exposed to the iSCSI initiator.
DIF is attached into data for write I/O and stripped from data for read I/O.

vhost

Added experimental support for running with the external, upstream rte_vhost library.
This can be enabled by configuring SPDK with an --without-internal-vhost-lib flag.
The minimum supported rte_vhost version (DPDK version) is 19.05-rc1.

As a result of fuzz testing, a lot of data races in vhost-scsi LUN hotplug path were identified and
fixed. Those data races could have potentially resulted in SPDK crashes, RPC hangs, or memory leaks
if Vhost-SCSI LUN hotplug RPCs were executed while connected VMs were in the middle of restarting.

The SCSI target id in add_vhost_scsi_lun RPC is now optional. If -1 is passed, the first
unoccupied target id will be used.

AIO

AIO bdev module can now reap I/O completions directly from userspace, significantly improving
the overall performance.

blobfs

Synchronous IO operations no longer use spdk_io_channel, but instead use
spdk_fs_thread_ctx. The behavior is otherwise identical.

OCF

Added support for caching multiple bdevs using a single bdev as a cache.

notify

Added the notify library that provides a high performance local event bus
between libraries. Example usage was added to bdev module, which reports
notifications for added and removed bdevs via RPC.

sock

Added new API spdk_sock_readv() to the sock library for performing vectored
reads.

event

The function spdk_subsystem_init() no longer requires spdk_event as an argument.

Changed API of spdk_subsystem_config_json() to no longer be asynchronous.

io_uring

A bdev module that issues I/O to kernel block devices using the new io_uring Linux kernel
API was added. This module requires liburing.

build

Options to easily compile with profile guided optimization have been added to
configure. To use profile guided optimization with SPDK, run
./configure --with-pgo-capture, build SPDK, then run a workload of your
choosing. Then, simply run ./configure --with-pgo-enable and recompile to
build using the generated profile data. Profile guided optimization can yield
very large performance improvements, especially on GCC 8 and clang 7. This may
be combined with link time optimization which has been available under the
--enable-lto configure option for several releases.

compression bdev/reduce library

Added "reduce" block compression scheme based on using SSDs for storing
compressed blocks of storage and presistent memory for metadata. Please see
compression for more details.