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2014-06-09blk-mq: always initialize request->start_timeJens Axboe
The blk-mq core only initializes this if io stats are enabled, since blk-mq only reads the field in that case. But drivers could potentially use it internally, so ensure that we always set it to the current time when the request is allocated. Reported-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-08block: blk-exec.c: Cleaning up local variable address returndRickard Strandqvist
Address of local variable assigned to a function parameter This was partly found using a static code analysis program called cppcheck. Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-06mm: convert some level-less printks to pr_*Mitchel Humpherys
printk is meant to be used with an associated log level. There are some instances of printk scattered around the mm code where the log level is missing. Add a log level and adhere to suggestions by scripts/checkpatch.pl by moving to the pr_* macros. Also add the typical pr_fmt definition so that print statements can be easily traced back to the modules where they occur, correlated one with another, etc. This will require the removal of some (now redundant) prefixes on a few print statements. Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-06-06blk-mq: ->timeout should be cleared in blk_mq_rq_ctx_init()Jens Axboe
It'll be used in blk_mq_start_request() to set a potential timeout for the request, so clear it to zero at alloc time to ensure that we know if someone has set it or not. Fixes random early timeouts on NVMe testing. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-06blk-mq: don't allow queue entering for a dying queueKeith Busch
If the queue is going away, don't let new allocs or queueing happen on it. Go through the normal wait process, and exit with ENODEV in that case. Signed-off-by: Keith Busch <keith.busch@intel.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-06blk-mq: bump max tag depth to 10K tagsJens Axboe
For some scsi-mq cases, the tag map can be huge. So increase the max number of tags we support. Additionally, don't fail with EINVAL if a user requests too many tags. Warn that the tag depth has been adjusted down, and store the new value inside the tag_set passed in. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-06block: add blk_rq_set_block_pc()Jens Axboe
With the optimizations around not clearing the full request at alloc time, we are leaving some of the needed init for REQ_TYPE_BLOCK_PC up to the user allocating the request. Add a blk_rq_set_block_pc() that sets the command type to REQ_TYPE_BLOCK_PC, and properly initializes the members associated with this type of request. Update callers to use this function instead of manipulating rq->cmd_type directly. Includes fixes from Christoph Hellwig <hch@lst.de> for my half-assed attempt. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-05block: add notion of a chunk size for request mergingJens Axboe
Some drivers have different limits on what size a request should optimally be, depending on the offset of the request. Similar to dividing a device into chunks. Add a setting that allows the driver to inform the block layer of such a chunk size. The block layer will then prevent merging across the chunks. This is needed to optimally support NVMe with a non-zero stripe size. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-04block: mq flush: clear flush_rq's tag in flush_end_io()Ming Lei
blk_mq_tag_to_rq() needs to be able to tell if it should return the original request, or the flush request if we are doing a flush sequence. Clear the flush tag when IO completes for a flush, since that is what we are comparing against. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-04blk-mq: let blk_mq_tag_to_rq() take blk_mq_tags as the main parameterJens Axboe
We currently pass in the hardware queue, and get the tags from there. But from scsi-mq, with a shared tag space, it's a lot more convenient to pass in the blk_mq_tags instead as the hardware queue isn't always directly available. So instead of having to re-map to a given hardware queue from rq->mq_ctx, just pass in the tags structure. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-04blk-mq: fix regression from commit 624dbe475416Jens Axboe
When the code was collapsed to avoid duplication, the recent patch for ensuring that a queue is idled before free was dropped, which was added by commit 19c5d84f14d2. Add back the blk_mq_tag_idle(), to ensure we don't leak a reference to an active queue when it is freed. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-03blk-mq: handle NULL req return from blk_map_request in single queue modeJens Axboe
blk_mq_map_request() can return NULL if we fail entering the queue (dying, or removed), in which case it has already ended IO on the bio. So nothing more to do, except just return. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-03blk-mq: fix sparse warning on missed __percpu annotationMing Lei
'struct blk_mq_ctx' is __percpu, so add the annotation and fix the sparse warning reported from Fengguang: [block:for-linus 2/3] block/blk-mq.h:75:16: sparse: incorrect type in initializer (different address spaces) Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-03blk-mq: fix schedule from atomic contextMing Lei
blk_mq_put_ctx() has to be called before io_schedule() in bt_get(). This patch fixes the problem by taking similar approach from percpu_ida allocation for the situation. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-03blk-mq: move blk_mq_get_ctx/blk_mq_put_ctx to mq private headerMing Lei
The blk-mq tag code need these helpers. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-06-03Merge branch 'locking-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next Pull core locking updates from Ingo Molnar: "The main changes in this cycle were: - reduced/streamlined smp_mb__*() interface that allows more usecases and makes the existing ones less buggy, especially in rarer architectures - add rwsem implementation comments - bump up lockdep limits" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits) rwsem: Add comments to explain the meaning of the rwsem's count field lockdep: Increase static allocations arch: Mass conversion of smp_mb__*() arch,doc: Convert smp_mb__*() arch,xtensa: Convert smp_mb__*() arch,x86: Convert smp_mb__*() arch,tile: Convert smp_mb__*() arch,sparc: Convert smp_mb__*() arch,sh: Convert smp_mb__*() arch,score: Convert smp_mb__*() arch,s390: Convert smp_mb__*() arch,powerpc: Convert smp_mb__*() arch,parisc: Convert smp_mb__*() arch,openrisc: Convert smp_mb__*() arch,mn10300: Convert smp_mb__*() arch,mips: Convert smp_mb__*() arch,metag: Convert smp_mb__*() arch,m68k: Convert smp_mb__*() arch,m32r: Convert smp_mb__*() arch,ia64: Convert smp_mb__*() ...
2014-06-02Merge branch 'for-3.16/drivers' of git://git.kernel.dk/linux-block into nextLinus Torvalds
Pull block driver changes from Jens Axboe: "Now that the core bits are in, here's the pull request for the driver related changes for 3.16. Nothing out of the ordinary here, mostly business as usual. There are a few pulls of for-3.16/core into this branch, which were done when the blk-mq was modified after the mtip32xx conversion was put in. The pull request contains: - skd and cciss converted to use pci_enable_msix_exact(). From Alexander Gordeev. - A few mtip32xx fixes from Asai @ Micron. - The conversion of mtip32xx from make_request_fn to blk-mq, and a later small fix for that conversion on quiescing for non-queued IO. From me. - A fix for bsg to use an exported function to check whether this driver is request based or not. Needed updating for blk-mq, which is request based, but does not have a request_fn hook. From me. - Small floppy bug fix from Jiri. - A series of cleanups for the cdrom uniform layer from Joe Perches. Gets rid of various old ugly macros, making the code conform more to the modern coding style. - A series of patches for drbd from the drbd crew (Lars Ellenberg and Philipp Reisner). - A use-after-free fix for null_blk from Ming Lei. - Also from Ming Lei is a performance patch for virtio-blk, which can net us a 3x win on kvm platforms where world notification is expensive. - Ming Lei also fixed a stall issue in virtio-blk, due to a race between queue start/stop and resource limits. - A small batch of fixes for xen-blk{back,front} from Olaf Hering and Valentin Priescu" * 'for-3.16/drivers' of git://git.kernel.dk/linux-block: (54 commits) block: virtio_blk: don't hold spin lock during world switch xen-blkback: defer freeing blkif to avoid blocking xenwatch xen blkif.h: fix comment typo in discard-alignment xen/blkback: disable discard feature if requested by toolstack xen-blkfront: remove type check from blkfront_setup_discard floppy: do not corrupt bio.bi_flags when reading block 0 mtip32xx: move error handling to service thread virtio_blk: fix race between start and stop queue mtip32xx: stop block hardware queues before quiescing IO mtip32xx: blk_mq_init_queue() returns an ERR_PTR mtip32xx: convert to use blk-mq cdrom: Remove unnecessary prototype for cdrom_get_disc_info cdrom: Remove unnecessary prototype for cdrom_mrw_exit cdrom: Remove cdrom_count_tracks prototype cdrom: Remove cdrom_get_next_writeable prototype cdrom: Remove cdrom_get_last_written prototype cdrom: Move mmc_ioctls above cdrom_ioctl to remove unnecessary prototype cdrom: Remove unnecessary sanitize_format prototype cdrom: Remove unnecessary check_for_audio_disc prototype cdrom: Remove prototype for open_for_data ...
2014-06-02Merge branch 'for-3.16/core' of git://git.kernel.dk/linux-block into nextLinus Torvalds
Pull block core updates from Jens Axboe: "It's a big(ish) round this time, lots of development effort has gone into blk-mq in the last 3 months. Generally we're heading to where 3.16 will be a feature complete and performant blk-mq. scsi-mq is progressing nicely and will hopefully be in 3.17. A nvme port is in progress, and the Micron pci-e flash driver, mtip32xx, is converted and will be sent in with the driver pull request for 3.16. This pull request contains: - Lots of prep and support patches for scsi-mq have been integrated. All from Christoph. - API and code cleanups for blk-mq from Christoph. - Lots of good corner case and error handling cleanup fixes for blk-mq from Ming Lei. - A flew of blk-mq updates from me: * Provide strict mappings so that the driver can rely on the CPU to queue mapping. This enables optimizations in the driver. * Provided a bitmap tagging instead of percpu_ida, which never really worked well for blk-mq. percpu_ida relies on the fact that we have a lot more tags available than we really need, it fails miserably for cases where we exhaust (or are close to exhausting) the tag space. * Provide sane support for shared tag maps, as utilized by scsi-mq * Various fixes for IO timeouts. * API cleanups, and lots of perf tweaks and optimizations. - Remove 'buffer' from struct request. This is ancient code, from when requests were always virtually mapped. Kill it, to reclaim some space in struct request. From me. - Remove 'magic' from blk_plug. Since we store these on the stack and since we've never caught any actual bugs with this, lets just get rid of it. From me. - Only call part_in_flight() once for IO completion, as includes two atomic reads. Hopefully we'll get a better implementation soon, as the part IO stats are now one of the more expensive parts of doing IO on blk-mq. From me. - File migration of block code from {mm,fs}/ to block/. This includes bio.c, bio-integrity.c, bounce.c, and ioprio.c. From me, from a discussion on lkml. That should describe the meat of the pull request. Also has various little fixes and cleanups from Dave Jones, Shaohua Li, Duan Jiong, Fengguang Wu, Fabian Frederick, Randy Dunlap, Robert Elliott, and Sam Bradshaw" * 'for-3.16/core' of git://git.kernel.dk/linux-block: (100 commits) blk-mq: push IPI or local end_io decision to __blk_mq_complete_request() blk-mq: remember to start timeout handler for direct queue block: ensure that the timer is always added blk-mq: blk_mq_unregister_hctx() can be static blk-mq: make the sysfs mq/ layout reflect current mappings blk-mq: blk_mq_tag_to_rq should handle flush request block: remove dead code in scsi_ioctl:blk_verify_command blk-mq: request initialization optimizations block: add queue flag for disabling SG merging block: remove 'magic' from struct blk_plug blk-mq: remove alloc_hctx and free_hctx methods blk-mq: add file comments and update copyright notices blk-mq: remove blk_mq_alloc_request_pinned blk-mq: do not use blk_mq_alloc_request_pinned in blk_mq_map_request blk-mq: remove blk_mq_wait_for_tags blk-mq: initialize request in __blk_mq_alloc_request blk-mq: merge blk_mq_alloc_reserved_request into blk_mq_alloc_request blk-mq: add helper to insert requests from irq context blk-mq: remove stale comment for blk_mq_complete_request() blk-mq: allow non-softirq completions ...
2014-05-30blk-mq: push IPI or local end_io decision to __blk_mq_complete_request()Jens Axboe
We have callers outside of the blk-mq proper (like timeouts) that want to call __blk_mq_complete_request(), so rename the function and put the decision code for whether to use ->softirq_done_fn or blk_mq_endio() into __blk_mq_complete_request(). This also makes the interface more logical again. blk_mq_complete_request() attempts to atomically mark the request completed, and calls __blk_mq_complete_request() if successful. __blk_mq_complete_request() then just ends the request. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-30blk-mq: remember to start timeout handler for direct queueJens Axboe
Commit 07068d5b8e added a direct-to-hw-queue mode, but this mode needs to remember to add the request timeout handler as well. Without it, we don't track timeouts for these requests. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-30block: ensure that the timer is always addedJens Axboe
Commit f793aa537866 relaxed the timer addition a little too much. If the timer isn't pending, we always need to add it. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-30blk-mq: blk_mq_unregister_hctx() can be staticFengguang Wu
CC: Jens Axboe <axboe@kernel.dk> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-30blk-mq: make the sysfs mq/ layout reflect current mappingsJens Axboe
Currently blk-mq registers all the hardware queues in sysfs, regardless of whether it uses them (e.g. they have CPU mappings) or not. The unused hardware queues lack the cpux/ directories, and the other sysfs entries (like active, pending, etc) are all zeroes. Change this so that sysfs correctly reflects the current mappings of the hardware queues. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-30Merge branch 'for-3.16/core' into for-3.16/driversJens Axboe
Pulled in for the blk_mq_tag_to_rq() change, which impacts mtip32xx. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-30blk-mq: blk_mq_tag_to_rq should handle flush requestShaohua Li
flush request is special, which borrows the tag from the parent request. Hence blk_mq_tag_to_rq needs special handling to return the flush request from the tag. Signed-off-by: Shaohua Li <shli@fusionio.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-29block: remove dead code in scsi_ioctl:blk_verify_commandDave Jones
filter gets assigned the address of blk_default_cmd_filter on entry to this function, so the !filter condition can never be true. Signed-off-by: Dave Jones <davej@redhat.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-29blk-mq: request initialization optimizationsJens Axboe
We currently clear a lot more than we need to, so make that a bit more clever. Make some of the init dependent on features, like only setting start_time if we are going to use it. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-29block: add queue flag for disabling SG mergingJens Axboe
If devices are not SG starved, we waste a lot of time potentially collapsing SG segments. Enough that 1.5% of the CPU time goes to this, at only 400K IOPS. Add a queue flag, QUEUE_FLAG_NO_SG_MERGE, which just returns the number of vectors in a bio instead of looping over all segments and checking for collapsible ones. Add a BLK_MQ_F_SG_MERGE flag so that drivers can opt-in on the sg merging, if they so desire. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-29block: remove 'magic' from struct blk_plugJens Axboe
I don't think we've ever caught any bugs with this, and there's the list poisoning for the plug lists to catch uninitialized cases. So remove the magic member and save 8 bytes in the struct. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28Merge branch 'for-3.16/core' into for-3.16/driversJens Axboe
Pull in core changes (again), since we got rid of the alloc/free hctx mq_ops hooks and mtip32xx then needed updating again. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: remove alloc_hctx and free_hctx methodsChristoph Hellwig
There is no need for drivers to control hardware context allocation now that we do the context to node mapping in common code. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: add file comments and update copyright noticesJens Axboe
None of the blk-mq files have an explanatory comment at the top for what that particular file does. Add that and add appropriate copyright notices as well. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28Merge branch 'for-3.16/core' into for-3.16/driversJens Axboe
mtip32xx uses blk_mq_alloc_reserved_request(), so pull in the core changes so we have a properly merged end result. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: remove blk_mq_alloc_request_pinnedChristoph Hellwig
We now only have one caller left and can open code it there in a cleaner way. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: do not use blk_mq_alloc_request_pinned in blk_mq_map_requestChristoph Hellwig
We already do a non-blocking allocation in blk_mq_map_request, no need to repeat it. Just call __blk_mq_alloc_request to wait directly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: remove blk_mq_wait_for_tagsChristoph Hellwig
The current logic for blocking tag allocation is rather confusing, as we first allocated and then free again a tag in blk_mq_wait_for_tags, just to attempt a non-blocking allocation and then repeat if someone else managed to grab the tag before us. Instead change blk_mq_alloc_request_pinned to simply do a blocking tag allocation itself and use the request we get back from it. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: initialize request in __blk_mq_alloc_requestChristoph Hellwig
Both callers if __blk_mq_alloc_request want to initialize the request, so lift it into the common path. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: merge blk_mq_alloc_reserved_request into blk_mq_alloc_requestChristoph Hellwig
Instead of having two almost identical copies of the same code just let the callers pass in the reserved flag directly. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-28blk-mq: add helper to insert requests from irq contextChristoph Hellwig
Both the cache flush state machine and the SCSI midlayer want to submit requests from irq context, and the current per-request requeue_work unfortunately causes corruption due to sharing with the csd field for flushes. Replace them with a per-request_queue list of requests to be requeued. Based on an earlier test by Ming Lei. Signed-off-by: Christoph Hellwig <hch@lst.de> Reported-by: Ming Lei <tom.leiming@gmail.com> Tested-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-27blk-mq: allow non-softirq completionsJens Axboe
Right now we export two ways of completing a request: 1) blk_mq_complete_request(). This uses an IPI (if needed) and completes through q->softirq_done_fn(). It also works with timeouts. 2) blk_mq_end_io(). This completes inline, and ignores any timeout state of the request. Let blk_mq_complete_request() handle non-softirq_done_fn completions as well, by just completing inline. If a driver has enough completion ports to place completions correctly, it need not define a mq_ops->complete() and we can avoid an indirect function call by doing the completion inline. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-27blk-mq: pass in suggested NUMA node to ->alloc_hctx()Jens Axboe
Drivers currently have to figure this out on their own, and they are missing information to do it properly. The ones that did attempt to do it, do it wrong. So just pass in the suggested node directly to the alloc function. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-27block: only allocate/free mq_usage_counter in blk-mqMing Lei
The percpu counter is only used for blk-mq, so move its allocation and free inside blk-mq, and don't allocate it for legacy queue device. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-27blk-mq: avoid code duplicationMing Lei
blk_mq_exit_hw_queues() and blk_mq_free_hw_queues() are introduced to avoid code duplication. Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-27blk-mq: fix leak of hctx->ctx_mapMing Lei
hctx->ctx_map should have been freed inside blk_mq_free_queue(). Signed-off-by: Ming Lei <tom.leiming@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-26block/blk-lib.c: make __blkdev_issue_zeroout staticFabian Frederick
__blkdev_issue_zeroout is only used in blk-lib.c Cc: Jens Axboe <axboe@kernel.dk> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Fabian Frederick <fabf@skynet.be> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-26blk-mq: idle all hardware contexts before freeing a queueChristoph Hellwig
Without this we can leak the active_queues reference if a command is freed while it is considered active. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-23blk-mq: allow setting of per-request timeoutsJens Axboe
Currently blk-mq uses the queue timeout for all requests. But for some commands, drivers may want to set a specific timeout for special requests. Allow this to be passed in through request->timeout, and use it if set. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-23blk-mq: export blk_mq_tag_busy_iterSam Bradshaw
Export the blk-mq in-flight tag iterator for driver consumption. This is particularly useful in exception paths or SRSI where in-flight IOs need to be cancelled and/or reissued. The NVMe driver conversion will use this. Signed-off-by: Sam Bradshaw <sbradshaw@micron.com> Signed-off-by: Matias Bjørling <m@bjorling.me> Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-22blk-mq: split make request handler for multi and single queueJens Axboe
We want slightly different behavior from them: - On single queue devices, we currently use the per-process plug for deferred IO and for merging. - On multi queue devices, we don't use the per-process plug, but we want to go straight to hardware for SYNC IO. Split blk_mq_make_request() into a blk_sq_make_request() for single queue devices, and retain blk_mq_make_request() for multi queue devices. Then we don't need multiple checks for q->nr_hw_queues in the request mapping. Signed-off-by: Jens Axboe <axboe@fb.com>
2014-05-21blk-mq: save memory by freeing requests on unused hardware queuesJens Axboe
Depending on the topology of the machine and the number of queues exposed by a device, we can end up in a situation where some of the hardware queues are unused (as in, they don't map to any software queues). For this case, free up the memory used by the request map, as we will not use it. This can be a substantial amount of memory, depending on the number of queues vs CPUs and the queue depth of the device. Signed-off-by: Jens Axboe <axboe@fb.com>