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.