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path: root/drivers/lightnvm/core.c
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2016-05-06lightnvm: rename nr_pages to nr_ppas on nvm_rqJavier González
The number of ppas contained on a request is not necessarily the number of pages that it maps to neither on the target nor on the device side. In order to avoid confusion, rename nr_pages to nr_ppas since it is what the variable actually contains. Signed-off-by: Javier González <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: remove mgt targets on mgt removalMatias Bjørling
Targets associated with a device manager are not freed on device removal. They have to be manually removed before shutdown. Make sure any outstanding targets are freed upon shutdown. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: rename dma helper functionsJavier González
Until now, the dma pool have been exclusively used to allocate the ppa list being sent to the device. In pblk (upcoming), we use these pools to allocate metadata too. Thus, we generalize the names of some variables on the dma helper functions to make the code more readable. Signed-off-by: Javier González <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: make nvm_set_rqd_ppalist() aware of vblksMatias Bjørling
A virtual block enables a block to identify multiple physical blocks. This is useful for metadata where a device media supports multiple planes. In that case, a block, with multiple planes can be managed as a single vblk. Reducing the metadata required by one forth. nvm_set_rqd_ppalist() takes care of expanding a ppa_list with vblks automatically. However, for some use-cases, where only a single physical block is required, the ppa_list should not be expanded. Therefore, add a vblk parameter to nvm_set_rqd_ppalist(), and only expand the ppa_list if vblk is set. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: refactor device ops->get_bb_tbl()Matias Bjørling
The device ops->get_bb_tbl() takes a callback, that allows the caller to use its own callback function to update its data structures in the returning function. This makes it difficult to send parameters to the callback, and usually is circumvented by small private structures, that both carry the callers state and any flags needed to fulfill the update. Refactor ops->get_bb_tbl() to fill a data buffer with the status of the blocks returned, and let the user call the callback function manually. That will provide the necessary flags and data structures and simplify the logic around ops->get_bb_tbl(). Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: refactor dev->online_target to global nvm_targetsSimon A. F. Lund
A target name must be unique. However, a per-device registration of targets is maintained on a dev->online_targets list, with a per-device search for targets upon registration. This results in a name collision when two targets, with the same name, are created on two different targets, where the per-device list is not shared. Signed-off-by: Simon A. F. Lund <slund@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: rename nvm_targets to nvm_tgt_typeSimon A. F. Lund
The functions nvm_register_target(), nvm_unregister_target() and associated list refers to a target type that is being registered by a target type module. Rename nvm_*_targets() to nvm_*_tgt_type(), so that the intension is clear. This enables target instances to use the _nvm_*_targets() naming. Signed-off-by: Simon A. F. Lund <slund@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: avoid memory leak when lun_map kcalloc failsMatias Bjørling
A memory leak occurs if the lower page table is initialized and the following dev->lun_map fails on allocation. Rearrange the initialization of lower page table to allow dev->lun_map to fail gracefully without memory leak. Reviewed by: Johannes Thumshirn <jthumshirn@suse.de> Move kfree of dev->lun_map to nvm_free() Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: move block fold outside of get_bb_tbl()Matias Bjørling
The get block table command returns a list of blocks and planes with their associated state. Users, such as gennvm and sysblk, manages all planes as a single virtual block. It was therefore natural to fold the bad block list before it is returned. However, to allow users, which manages on a per-plane block level, to also use the interface, the get_bb_tbl interface is changed to not fold by default and instead let the caller fold if necessary. Reviewed by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: add fpg_size and pfpg_size to struct nvm_devMatias Bjørling
The flash page size (fpg) and size across planes (pfpg) are convenient to know when allocating buffer sizes. This has previously been a calculated in various places. Replace with the pre-calculated values. Reviewed by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: implement nvm_submit_ppa_listMatias Bjørling
The nvm_submit_ppa function assumes that users manage all plane blocks as a single block. Extend the API with nvm_submit_ppa_list to allow the user to send its own ppa list. If the user submits more than a single PPA, the user must take care to allocate and free the corresponding ppa list. Reviewed by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-05-06lightnvm: handle submit_io failureMatias Bjørling
The device ->submit_io() callback might fail to submit I/O to device. In that case, the nvm_submit_ppa function should not wait for completion. Instead return the ->submit_io() error. Reviewed by: Johannes Thumshirn <jthumshirn@suse.de> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-03-18lightnvm: add a bitmap of lunsWenwei Tao
Add a bitmap of luns to indicate the status of luns: inuse/available. When create targets do the necessary check to avoid allocating luns that are already allocated. Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com> Freed dev->lun_map if nvm_core_init later failed in the init process. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-03-18lightnvm: specify target's logical address areaWenwei Tao
We can create more than one target on a lightnvm device by specifying its begin lun and end lun. But only specify the physical address area is not enough, we need to get the corresponding non- intersection logical address area division from the backend device's logcial address space. Otherwise the targets on the device might use the same logical addresses cause incorrect information in the device's l2p table. Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-03-18Merge branch 'for-4.6/drivers' of git://git.kernel.dk/linux-blockLinus Torvalds
Pull block driver updates from Jens Axboe: "This is the block driver pull request for this merge window. It sits on top of for-4.6/core, that was just sent out. This contains: - A set of fixes for lightnvm. One from Alan, fixing an overflow, and the rest from the usual suspects, Javier and Matias. - A set of fixes for nbd from Markus and Dan, and a fixup from Arnd for correct usage of the signed 64-bit divider. - A set of bug fixes for the Micron mtip32xx, from Asai. - A fix for the brd discard handling from Bart. - Update the maintainers entry for cciss, since that hardware has transferred ownership. - Three bug fixes for bcache from Eric Wheeler. - Set of fixes for xen-blk{back,front} from Jan and Konrad. - Removal of the cpqarray driver. It has been disabled in Kconfig since 2013, and we were initially scheduled to remove it in 3.15. - Various updates and fixes for NVMe, with the most important being: - Removal of the per-device NVMe thread, replacing that with a watchdog timer instead. From Christoph. - Exposing the namespace WWID through sysfs, from Keith. - Set of cleanups from Ming Lin. - Logging the controller device name instead of the underlying PCI device name, from Sagi. - And a bunch of fixes and optimizations from the usual suspects in this area" * 'for-4.6/drivers' of git://git.kernel.dk/linux-block: (49 commits) NVMe: Expose ns wwid through single sysfs entry drivers:block: cpqarray clean up brd: Fix discard request processing cpqarray: remove it from the kernel cciss: update MAINTAINERS NVMe: Remove unused sq_head read in completion path bcache: fix cache_set_flush() NULL pointer dereference on OOM bcache: cleaned up error handling around register_cache() bcache: fix race of writeback thread starting before complete initialization NVMe: Create discard zero quirk white list nbd: use correct div_s64 helper mtip32xx: remove unneeded variable in mtip_cmd_timeout() lightnvm: generalize rrpc ppa calculations lightnvm: remove struct nvm_dev->total_blocks lightnvm: rename ->nr_pages to ->nr_sects lightnvm: update closed list outside of intr context xen/blback: Fit the important information of the thread in 17 characters lightnvm: fold get bb tbl when using dual/quad plane mode lightnvm: fix up nonsensical configure overrun checking xen-blkback: advertise indirect segment support earlier ...
2016-03-03lightnvm: remove struct nvm_dev->total_blocksMatias Bjørling
The struct nvm_dev->total_blocks was only used for calculating total sectors. Remove and instead calculate total sectors from the number of luns and its sectors. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-03-03lightnvm: rename ->nr_pages to ->nr_sectsMatias Bjørling
The struct rrpc->nr_pages can easily be interpreted as the number of flash pages allocated to rrpc, while it is the nr_sects. Make sure that this is reflected from the variable name. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-03-03lightnvm: fold get bb tbl when using dual/quad plane modeMatias Bjørling
When the media manager runs in dual or quad plane mode, lightnvm abstracts away plane specific commands. This poses a problem for get bad block table, as it reports bad blocks per plane, making the table either two or four times bigger than expected. Fold the bad block list before returning. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-03-03lightnvm: fix up nonsensical configure overrun checkingAlan
Instead of checking a constant 0 actually check the space available. Even better remember to allow for the header and also check the right amount of space is needed. Signed-off-by: Alan Cox <alan@linux.intel.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-02-04lightnvm: allow to force mm initializationMatias Bjørling
System block allows the device to initialize with its configured media manager. The system blocks is written to disk, and read again when media manager is determined. For this to work, the backend must store the data. Device drivers, such as null_blk, does not have any backend storage. This patch allows the media manager to be initialized without a storage backend. It also fix incorrect configuration of capabilities in null_blk, as it does not support get/set bad block interface. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: introduce factory resetMatias Bjørling
Now that a device can be managed using the system blocks, a method to reset the device is necessary as well. This patch introduces logic to reset the device easily to factory state and exposes it through an ioctl. The ioctl takes the following flags: NVM_FACTORY_ERASE_ONLY_USER By default all blocks, except host-reserved blocks are erased upon factory reset. Instead of this, only erase host-reserved blocks. NVM_FACTORY_RESET_HOST_BLKS Mark host-reserved blocks to be erased and set their type to free. NVM_FACTORY_RESET_GRWN_BBLKS Mark "grown bad blocks" to be erased and set their type to free. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: use system block for mm initializationMatias Bjørling
Use system block information to register the appropriate media manager. This enables the LightNVM subsystem to instantiate a media manager selected by the user, instead of relying on automatic detection by each media manager loaded in the kernel. A device must now be initialized before it can proceed to initialize its media manager. Upon initialization, the configured media manager is automatically initialized as well. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: introduce ioctl to initialize deviceMatias Bjørling
Based on the previous patch, we now introduce an ioctl to initialize the device using nvm_init_sysblock and create the necessary system blocks. The user may specify the media manager that they wish to instantiate on top. Default from user-space will be "gennvm". Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: core on-disk initializationMatias Bjørling
An Open-Channel SSD shall be initialized before use. To initialize, we define an on-disk format, that keeps a small set of metadata to bring up the media manager on top of the device. The initial step is introduced to allow a user to format the disks for a given media manager. During format, a system block is stored on one to three separate luns on the device. Each lun has the system block duplicated. During initialization, the system block can be retrieved and the appropriate media manager can initialized. The on-disk format currently covers (struct nvm_system_block): - Magic value "NVMS". - Monotonic increasing sequence number. - The physical block erase count. - Version of the system block format. - Media manager type. - Media manager superblock physical address. The interface provides three functions to manage the system block: int nvm_init_sysblock(struct nvm_dev *, struct nvm_sb_info *) int nvm_get_sysblock(struct nvm *dev, struct nvm_sb_info *) int nvm_update_sysblock(struct nvm *dev, struct nvm_sb_info *) Each implement a part of the logic to manage the system block. The initialization creates the first system blocks and mark them on the device. Get retrieves the latest system block by scanning all pages in the associated system blocks. The update sysblock writes new metadata and allocates new block if necessary. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: introduce mlc lower page table mappingsMatias Bjørling
NAND MLC memories have both lower and upper pages. When programming, both of these must be written, before data can be read. However, these lower and upper pages might not placed at even and odd flash pages, but can be skipped. Therefore each flash memory has its lower pages defined, which can then be used when programming and to know when padding are necessary. This patch implements the lower page definition in the specification, and exposes it through a simple lookup table at dev->lptbl. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: add mccap supportMatias Bjørling
Some flash media has extended capabilities, such as programming SLC pages on MLC/TLC flash, erase/program suspend, scramble and encryption. MCCAP is introduced to detect support for these capabilities in the command set. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: manage open and closed blocks separatelyJavier González
LightNVM targets need to know the state of the flash block when doing flash optimizations. An example is implementing a write buffer to respect the flash page size. Currently, block state is not accounted for; the media manager only differentiates among free, bad and in-use blocks. This patch adds the logic in the generic media manager to enable targets manage blocks into open and close separately, and it implements such management in rrpc. It also adds a set of flags to describe the state of the block (open, closed, free, bad). In order to avoid taking two locks (nvm_lun and rrpc_lun) consecutively, we introduce lockless get_/put_block primitives so that the open and close list locks and future common logic is handled within the nvm_lun lock. Signed-off-by: Javier González <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: introduce nvm_submit_ppaMatias Bjørling
Internal logic for both core and media managers, does not have a backing bio for issuing I/Os. Introduce nvm_submit_ppa to allow raw I/Os to be submitted to the underlying device driver. The function request the device, ppa, data buffer and its length and will submit the I/O synchronously to the device. The return value may therefore be used to detect any errors regarding the issued I/O. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: move rq->error to nvm_rq->errorMatias Bjørling
Instead of passing request error into the LightNVM modules, incorporate it into the nvm_rq. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: support multiple ppas in nvm_erase_ppaMatias Bjørling
Sometimes a user want to erase multiple PPAs at the same time. Extend nvm_erase_ppa to take multiple ppas and number of ppas to be erased. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: sectors first in ppa listMatias Bjørling
The Westlake controller requires that the PPA list has sectors defined sequentially. Currently, the PPA list is created with planes first, then sectors. Change this to sectors first, then planes. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: refactor end_io functions for syncMatias Bjørling
To implement sync I/O support within the LightNVM core, the end_io functions are refactored to take an end_io function pointer instead of testing for initialized media manager, followed by calling its end_io function. Sync I/O can then be implemented using a callback that signal I/O completion. This is similar to the logic found in blk_to_execute_io(). By implementing it this way, the underlying device I/Os submission logic is abstracted away from core, targets, and media managers. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: refactor rqd ppa list into set/freeMatias Bjørling
A device may be driven in single, double or quad plane mode. In that case, the rqd must have either one, two, or four PPAs set for a single PPA sent to the device. Refactor this logic into their own functions to be shared by program/erase/read in the core. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2016-01-12lightnvm: move ppa erase logic to coreMatias Bjørling
A device may function in single, dual or quad plane mode. The gennvm media manager manages this with explicit helpers. They convert a single ppa to 1, 2 or 4 separate ppas in a ppa list. To aid implementation of recovery and system blocks, this functionality can be moved directly into the core. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-12-07lightnvm: fix media mgr registrationMatias Bjørling
This patch fixes two issues during media manager registration. 1. The ppa pool can be used at media manager registration. Allocate the ppa pool before that. 2. If a media manager can't be found, this should not lead to the device being unallocated. A media manager can be registered later, that can manage the device. Only warn if a media manager fails initialization. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-12-07lightnvm: replace req queue with nvmdev for lldMatias Bjørling
In the case where a request queue is passed to the low lever lightnvm device drive integration, the device driver might pass its admin commands through another queue. Instead pass nvm_dev, and let the low level drive the appropriate queue. Reported-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-29lightnvm: missing nvm_lock acquireWenwei Tao
To avoid race conditions, traverse dev, media manager, and target lists and also register, unregister entries to/from them, should be always under the nvm_lock control. Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-29lightnvm: do device max sectors boundary check firstWenwei Tao
do device max_phys_sect boundary check first, otherwise we will allocate dma_pools for devices whose max sectors are beyond lightnvm support and register them. Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-29lightnvm: fix ioctl memory leaksSudip Mukherjee
If copy_to_user() fails we returned error but we missed releasing devices. Signed-off-by: Sudip Mukherjee <sudip@vectorindia.org> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-20lightnvm: add free and bad lun info to show lunsJavier Gonzalez
Add free block, used block, and bad block information to the show debug interface. This information is used to debug how targets track blocks. Also, change debug function name to make it more generic. Signed-off-by: Javier Gonzalez <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-20lightnvm: missing free on init errorMatias Bjørling
If either max_phys_sect is out of bound, the nvm_dev structure is not freed. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-20lightnvm: wrong return value and redundant freeWenwei Tao
The return value should be non-zero under error conditions. Remove nvme_free(dev) to avoid free dev more than once. Signed-off-by: Wenwei Tao <ww.tao0320@gmail.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-16lightnvm: cleanup queue before target removalJavier González
This prevents outstanding IOs to be sent for completion to target after the target has been removed. The flow is now: stop new IOs > cleanup queue > remove target. Signed-off-by: Javier Gonzalez <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-16lightnvm: remove linear and device addr modesMatias Bjørling
The linear and device specific address modes can be replaced with a simple offset and bit length conversion that is generic across all devices. This both simplifies the specification and removes the special case for qemu nvme, that previously relied on the linear address mapping. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-16lightnvm: prevent double free on init errorMatias Bjørling
Both the nvm_register and nvm_init does a kfree(dev) on error. Make sure to only free it once. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-16lightnvm: prematurely activate nvm_devMatias Bjørling
We register with nvm_devices when there registration can still fail. Move the final registration at the end of the nvm_register function to make sure we are fully registered when added to the nvm_devices list. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-11-16lightnvm: check for NAND flash and its typeMatias Bjørling
Only NAND flash with SLC and MLC is supported. Make sure to not try to initialize TLC memory or other non-volatile memory types. Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2015-10-29lightnvm: Support for Open-Channel SSDsMatias Bjørling
Open-channel SSDs are devices that share responsibilities with the host in order to implement and maintain features that typical SSDs keep strictly in firmware. These include (i) the Flash Translation Layer (FTL), (ii) bad block management, and (iii) hardware units such as the flash controller, the interface controller, and large amounts of flash chips. In this way, Open-channels SSDs exposes direct access to their physical flash storage, while keeping a subset of the internal features of SSDs. LightNVM is a specification that gives support to Open-channel SSDs LightNVM allows the host to manage data placement, garbage collection, and parallelism. Device specific responsibilities such as bad block management, FTL extensions to support atomic IOs, or metadata persistence are still handled by the device. The implementation of LightNVM consists of two parts: core and (multiple) targets. The core implements functionality shared across targets. This is initialization, teardown and statistics. The targets implement the interface that exposes physical flash to user-space applications. Examples of such targets include key-value store, object-store, as well as traditional block devices, which can be application-specific. Contributions in this patch from: Javier Gonzalez <jg@lightnvm.io> Dongsheng Yang <yangds.fnst@cn.fujitsu.com> Jesper Madsen <jmad@itu.dk> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>