linux/drivers/lightnvm/Kconfig
Javier González a4bd217b43 lightnvm: physical block device (pblk) target
This patch introduces pblk, a host-side translation layer for
Open-Channel SSDs to expose them like block devices. The translation
layer allows data placement decisions, and I/O scheduling to be
managed by the host, enabling users to optimize the SSD for their
specific workloads.

An open-channel SSD has a set of LUNs (parallel units) and a
collection of blocks. Each block can be read in any order, but
writes must be sequential. Writes may also fail, and if a block
requires it, must also be reset before new writes can be
applied.

To manage the constraints, pblk maintains a logical to
physical address (L2P) table,  write cache, garbage
collection logic, recovery scheme, and logic to rate-limit
user I/Os versus garbage collection I/Os.

The L2P table is fully-associative and manages sectors at a
4KB granularity. Pblk stores the L2P table in two places, in
the out-of-band area of the media and on the last page of a
line. In the cause of a power failure, pblk will perform a
scan to recover the L2P table.

The user data is organized into lines. A line is data
striped across blocks and LUNs. The lines enable the host to
reduce the amount of metadata to maintain besides the user
data and makes it easier to implement RAID or erasure coding
in the future.

pblk implements multi-tenant support and can be instantiated
multiple times on the same drive. Each instance owns a
portion of the SSD - both regarding I/O bandwidth and
capacity - providing I/O isolation for each case.

Finally, pblk also exposes a sysfs interface that allows
user-space to peek into the internals of pblk. The interface
is available at /dev/block/*/pblk/ where * is the block
device name exposed.

This work also contains contributions from:
  Matias Bjørling <matias@cnexlabs.com>
  Simon A. F. Lund <slund@cnexlabs.com>
  Young Tack Jin <youngtack.jin@gmail.com>
  Huaicheng Li <huaicheng@cs.uchicago.edu>

Signed-off-by: Javier González <javier@cnexlabs.com>
Signed-off-by: Matias Bjørling <matias@cnexlabs.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
2017-04-16 10:06:33 -06:00

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#
# Open-Channel SSD NVM configuration
#
menuconfig NVM
bool "Open-Channel SSD target support"
depends on BLOCK && HAS_DMA
help
Say Y here to get to enable Open-channel SSDs.
Open-Channel SSDs implement a set of extension to SSDs, that
exposes direct access to the underlying non-volatile memory.
If you say N, all options in this submenu will be skipped and disabled
only do this if you know what you are doing.
if NVM
config NVM_DEBUG
bool "Open-Channel SSD debugging support"
default n
---help---
Exposes a debug management interface to create/remove targets at:
/sys/module/lnvm/parameters/configure_debug
It is required to create/remove targets without IOCTLs.
config NVM_RRPC
tristate "Round-robin Hybrid Open-Channel SSD target"
---help---
Allows an open-channel SSD to be exposed as a block device to the
host. The target is implemented using a linear mapping table and
cost-based garbage collection. It is optimized for 4K IO sizes.
config NVM_PBLK
tristate "Physical Block Device Open-Channel SSD target"
---help---
Allows an open-channel SSD to be exposed as a block device to the
host. The target assumes the device exposes raw flash and must be
explicitly managed by the host.
Please note the disk format is considered EXPERIMENTAL for now.
endif # NVM