Resources are reallocated for requeued commands, so unmap and release
the iod for the failed command.
It's a pretty bad memory leak and causes a kernel hang if you remove a
drive because of a busy dma pool. You'll get messages spewing like this:
nvme 0000:xx:xx.x: dma_pool_destroy prp list 256, ffff880420dec000 busy
and lock up pci and the driver since removal never completes while
holding a lock.
Cc: stable@vger.kernel.org
Cc: <stable@vger.kernel.org> # 4.0.x-
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Use a separate integer variable to hold the signed Linux errno
values we pass back to the block layer. Note that for pass through
commands those might still be NVMe values, but those fit into the
int as well.
Fixes: f4829a9b7a61: ("blk-mq: fix racy updates of rq->errors")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Compiling the nvme driver on 32-bit warns about a cast from a __u64
variable to a pointer:
drivers/block/nvme-core.c: In function 'nvme_submit_io':
drivers/block/nvme-core.c:1847:4: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
(void __user *)io.addr, length, NULL, 0);
The cast here is intentional and safe, so we can shut up the
gcc warning by adding an intermediate cast to 'uintptr_t'.
I had previously submitted a patch to fix this problem in the
nvme driver, but it was accepted on the same day that two new
warnings got added.
For clarification, I also change the third instance of this cast
to use uintptr_t instead of unsigned long now.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: d29ec8241c ("nvme: submit internal commands through the block layer")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
blk_mq_complete_request may be a no-op if the request has already
been completed by others means (e.g. a timeout or cancellation), but
currently drivers have to set rq->errors before calling
blk_mq_complete_request, which might leave us with the wrong error value.
Add an error parameter to blk_mq_complete_request so that we can
defer setting rq->errors until we known we won the race to complete the
request.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The asynchronous namespace scanning caused affinity hints to be set before
its tagset initialized, so there was no cpu mask to set the hint. This
patch moves the affinity hint setting to after namespaces are scanned.
Reported-by: 김경산 <ks0204.kim@samsung.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Pull block driver updates from Jens Axboe:
"On top of the 4.3 core block IO changes, here are the driver related
changes for 4.3. Basically just NVMe and nbd this time around:
- NVMe:
- PRACT PI improvement from Alok Pandey.
- Cleanups and improvements on submission queue doorbell and
writing, using CMB if available. From Jon Derrick.
- From Keith, support for setting queue maximum segments, and
reset support.
- Also from Jon, fixup of u64 division issue on 32-bit archs and
wiring up of the reset support through and ioctl.
- Two small cleanups from Matias and Sunad
- Various code cleanups and fixes from Markus Pargmann"
* 'for-4.3/drivers' of git://git.kernel.dk/linux-block:
NVMe: Using PRACT bit to generate and verify PI by controller
NVMe:Remove unreachable code in nvme_abort_req
NVMe: Add nvme subsystem reset IOCTL
NVMe: Add nvme subsystem reset support
NVMe: removed unused nn var from nvme_dev_add
NVMe: Set queue max segments
nbd: flags is a u32 variable
nbd: Rename functions for clearness of recv/send path
nbd: Change 'disconnect' to be boolean
nbd: Add debugfs entries
nbd: Remove variable 'pid'
nbd: Move clear queue debug message
nbd: Remove 'harderror' and propagate error properly
nbd: restructure sock_shutdown
nbd: sock_shutdown, remove conditional lock
nbd: Fix timeout detection
nvme: Fixes u64 division which breaks i386 builds
NVMe: Use CMB for the IO SQes if available
NVMe: Unify SQ entry writing and doorbell ringing
This patch enables the PRCHK and reftag support when PRACT bit is set, and
block layer integrity is disabled.
Signed-off-by: Alok Pandey <pandey.alok@samsung.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Removing unreachable code from nvme_abort_req as nvme_submit_cmd has no
failure status to return.
Signed-off-by: Sunad Bhandary <sunad.s@samsung.com>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The SG_GAPS queue flag caused checks for bio vector alignment against
PAGE_SIZE, but the device may have different constraints. This patch
adds a queue limits so a driver with such constraints can set to allow
requests that would have been unnecessarily split. The new gaps check
takes the request_queue as a parameter to simplify the logic around
invoking this function.
This new limit makes the queue flag redundant, so removing it and
all usage. Device-mappers will inherit the correct settings through
blk_stack_limits().
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Controllers can perform optional subsystem resets as introduced in NVMe
1.1. This patch adds an IOCTL to trigger the subsystem reset by writing
"NVMe" to the NSSR register.
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Controllers part of an NVMe subsystem may be reset by any other controller
in the subsystem. If the device is capable of subsystem resets, this
patch adds detection for such events and performs appropriate controller
initialization upon subsystem reset detection.
The register bit is a RW1C type, so the driver needs to write a 1 to the
status bit to clear the subsystem reset occured bit during initialization.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The logic in nvme_dev_add to enumerate namespaces was moved to
nvme_dev_scan. When moved, the nn variable is no longer used. This patch
removes it.
Fixes: a5768aai ("NVMe: Automatic namespace rescan")
Signed-off-by: Matias Bjørling <m@bjorling.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This sets the queue's max segment size to match the device's
capabilities. The default of 128 is usable until a device's transfer
capability exceeds 512k, assuming a device page size of 4k. Many nvme
devices exceed that transfer limit, so this lets the block layer know what
kind of commands it to allow to form rather than unnecessarily split them.
One additional segment is added to account for a transfer that may start
in the middle of a page.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Uses div_u64 for u64 division and round_down, a bitwise operation,
instead of rounddown, which uses a modulus.
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Some controllers have a controller-side memory buffer available for use
for submissions, completions, lists, or data.
If a CMB is available, the entire CMB will be ioremapped and it will
attempt to map the IO SQes onto the CMB. The queues will be shrunk as
needed. The CMB will not be used if the queue depth is shrunk below some
threshold where it may have reduced performance over a larger queue
in system memory.
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
This patch changes sq_cmd writers to instead create their command on
the stack. __nvme_submit_cmd copies the sq entry to the queue and writes
the doorbell.
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Some drivers use it now, others just set the limits field manually.
But in preparation for splitting this into a hard and soft limit,
ensure that they all call the proper function for setting the hw
limit for discards.
Reviewed-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This patch has the driver automatically reread partitions if a namespace
has a separate metadata format. Previously revalidating a disk was
sufficient to get the correct capacity set on such formatted drives,
but partitions that may exist would not have been surfaced.
Reported-by: Paul Grabinar <paul.grabinar@ranbarg.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Tested-by: Paul Grabinar <paul.grabinar@ranbarg.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Fixes an issue when queue_reuest_irq fails in nvme_setup_io_queues. This
patch initializes all vectors to -1 and resets the vector to -1 in the
case of a failure in queue_request_irq. This avoids the free_irq in
nvme_suspend_queue if the queue did not get an irq.
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
gcc-4.4.4 (and possibly other versions) fail the compile when initializers
are used with anonymous unions. Work around this.
drivers/block/nvme-core.c: In function 'nvme_identify_ctrl':
drivers/block/nvme-core.c:1163: error: unknown field 'identify' specified in initializer
drivers/block/nvme-core.c:1163: warning: missing braces around initializer
drivers/block/nvme-core.c:1163: warning: (near initialization for 'c.<anonymous>')
drivers/block/nvme-core.c:1164: error: unknown field 'identify' specified in initializer
drivers/block/nvme-core.c:1164: warning: excess elements in struct initializer
drivers/block/nvme-core.c:1164: warning: (near initialization for 'c')
...
This patch has no effect on text size with gcc-4.8.2.
Fixes: d29ec8241c ("nvme: submit internal commands through the block layer")
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <axboe@fb.com>
Move gendisk deletion before controller shutdown so filesystem may sync
dirty pages. Before, this would deadlock trying to allocate requests
on frozen queues that are about to be deleted.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This fixes an infinite device reset loop that may occur on devices that
fail initialization. If the drive fails to become ready for any reason
that does not involve an admin command timeout, the probe task should
assume the drive is unavailable and remove it from the topology. In
the case an admin command times out during device probing, the driver's
existing reset action will handle removing the drive.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This unifies probe and resume so they both may be scheduled in the same
way. This is necessary for error handling that may occur during device
initialization since the task to cleanup the device wouldn't be able to
run if it is blocked on device initialization.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Synchronized commands do different things for timed out commands
vs. controller returned errors.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Don't release block queue and tagging resoureces if the driver never
got them in the first place. This can happen if the controller fails to
become ready, if memory wasn't available to allocate a tagset or admin
queue, or if the resources were released as part of error recovery.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Pull block driver updates from Jens Axboe:
"This contains:
- a few race fixes for null_blk, from Akinobu Mita.
- a series of fixes for mtip32xx, from Asai Thambi and Selvan Mani at
Micron.
- NVMe:
* Fix for missing error return on allocation failure, from Axel
Lin.
* Code consolidation and cleanups from Christoph.
* Memory barrier addition, syncing queue count and queue
pointers. From Jon Derrick.
* Various fixes from Keith, an addition to support user
issue reset from sysfs or ioctl, and automatic namespace
rescan.
* Fix from Matias, avoiding losing some request flags when
marking the request failfast.
- small cleanups and sparse fixups for ps3vram. From Geert
Uytterhoeven and Geoff Lavand.
- s390/dasd dead code removal, from Jarod Wilson.
- a set of fixes and optimizations for loop, from Ming Lei.
- conversion to blkdev_reread_part() of loop, dasd, ndb. From Ming
Lei.
- updates to cciss. From Tomas Henzl"
* 'for-4.2/drivers' of git://git.kernel.dk/linux-block: (44 commits)
mtip32xx: Fix accessing freed memory
block: nvme-scsi: Catch kcalloc failure
NVMe: Fix IO for extended metadata formats
nvme: don't overwrite req->cmd_flags on sync cmd
mtip32xx: increase wait time for hba reset
mtip32xx: fix minor number
mtip32xx: remove unnecessary sleep in mtip_ftl_rebuild_poll()
mtip32xx: fix crash on surprise removal of the drive
mtip32xx: Abort I/O during secure erase operation
mtip32xx: fix incorrectly setting MTIP_DDF_SEC_LOCK_BIT
mtip32xx: remove unused variable 'port->allocated'
mtip32xx: fix rmmod issue
MAINTAINERS: Update ps3vram block driver
block/ps3vram: Remove obsolete reference to MTD
block/ps3vram: Fix sparse warnings
NVMe: Automatic namespace rescan
NVMe: Memory barrier before queue_count is incremented
NVMe: add sysfs and ioctl controller reset
null_blk: restart request processing on completion handler
null_blk: prevent timer handler running on a different CPU where started
...
This fixes io submit ioctl handling when using extended metadata
formats. When these formats are used, the user provides a single virtually
contiguous buffer containing both the block and metadata interleaved,
so the metadata size needs to be added to the total length and not mapped
as a separate transfer.
The command is also driver generated, so this patch does not enforce
blk-integrity extensions provide the metadata buffer.
Reported-by: Marcin Dziegielewski <marcin.dziegielewski@intel.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
In __nvme_submit_sync_cmd, the request direction is overwritten when
the REQ_FAILFAST_DRIVER flag is set.
Signed-off-by: Matias Bjørling <m@bjorling.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Fixes: 75619bfa90 ("NVMe: End sync requests immediately on failure")
Signed-off-by: Jens Axboe <axboe@fb.com>
Namespaces may be dynamically allocated and deleted or attached and
detached. This has the driver rescan the device for namespace changes
after each device reset or namespace change asynchronous event.
There could potentially be many detached namespaces that we don't want
polluting /dev/ with unusable block handles, so this will delete disks
if the namespace is not active as indicated by the response from identify
namespace. This also skips adding the disk if no capacity is provisioned
to the namespace in the first place.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Protects against reordering and/or preempting which would allow the
kthread to access the queue descriptor before it is set up
Signed-off-by: Jon Derrick <jonathan.derrick@intel.com>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
We need the ability to perform an nvme controller reset as discussed on
the mailing list thread:
http://lists.infradead.org/pipermail/linux-nvme/2015-March/001585.html
This adds a sysfs entry that when written to will reset perform an NVMe
controller reset if the controller was successfully initialized in the
first place.
This also adds locking around resetting the device in the async probe
method so the driver can't schedule two resets.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Brandon Schultz <brandon.schulz@hgst.com>
Cc: David Sariel <david.sariel@pmcs.com>
Updated by Jens to:
1) Merge this with the ioctl reset patch from David Sariel. The ioctl
path now shares the reset code from the sysfs path.
2) Don't flush work if we fail issuing the reset.
Signed-off-by: Jens Axboe <axboe@fb.com>
The driver needs to track shared tags to support multiple namespaces
that may be dynamically allocated or deleted. Relying on the first
request_queue's hctx's is not appropriate as we cannot clear outstanding
tags for all namespaces using this handle, nor can the driver easily track
all request_queue's hctx as namespaces are attached/detached. Instead,
this patch uses the nvme_dev's tagset to get the shared tag resources
instead of through a request_queue hctx.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Do not retry failed sync commands so the original status may be seen
without issuing unnecessary retries.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
A recent change to the ioctl handling caused a new harmless
warning in the NVMe driver on all 32-bit machines:
drivers/block/nvme-core.c: In function 'nvme_submit_io':
drivers/block/nvme-core.c:1794:29: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
In order to shup up that warning, this introduces a new
temporary variable that uses a double cast to extract
the pointer from an __u64 structure member.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: a67a95134f ("NVMe: Meta data handling through submit io ioctl")
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Replaces req->sense_len usage, which is not owned by the LLD, to
req->special to contain the command result for driver created commands,
and sets the result unconditionally on completion.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@fb.com>
Fixes: d29ec8241c ("nvme: submit internal commands through the block layer")
Signed-off-by: Jens Axboe <axboe@fb.com>
Use block layer queues with an internal cmd_type to submit internally
generated NVMe commands. This both simplifies the code a lot and allow
for a better structure. For example now the LighNVM code can construct
commands without knowing the details of the underlying I/O descriptors.
Or a future NVMe over network target could inject commands, as well as
could the SCSI translation and ioctl code be reused for such a beast.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Most users want the generic device, so store that in struct nvme_dev
instead of the pci_dev. This also happens to be a nice step towards
making some code reusable for non-PCI transports.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Note that we keep the unused timeout argument, but allow callers to
pass 0 instead of a timeout if they want the default. This will allow
adding a timeout to the pass through path later on.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
The queue_lock needs to be taken with irqs disabled. This is mostly
due to the old pre blk-mq usage pattern, but we've also picked it up
in most of the few places where we use the queue_lock with blk-mq.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Pull block driver updates from Jens Axboe:
"This is the block driver pull request for 4.1. As with the core bits,
this is a relatively slow round. This pull request contains:
- Various fixes and cleanups for NVMe, from Alexey Khoroshilov, Chong
Yuan, myself, Keith Busch, and Murali Iyer.
- Documentation and code cleanups for nbd from Markus Pargmann.
- Change of brd maintainer to me, from Ross Zwisler. At least the
email doesn't bounce anymore then.
- Two xen-blkback fixes from Tao Chen"
* 'for-4.1/drivers' of git://git.kernel.dk/linux-block: (23 commits)
NVMe: Meta data handling through submit io ioctl
NVMe: Add translation for block limits
NVMe: Remove check for null
NVMe: Fix error handling of class_create("nvme")
xen-blkback: define pr_fmt macro to avoid the duplication of DRV_PFX
xen-blkback: enlarge the array size of blkback name
nbd: Return error pointer directly
nbd: Return error code directly
nbd: Remove fixme that was already fixed
nbd: Restructure debugging prints
nbd: Fix device bytesize type
nbd: Replace kthread_create with kthread_run
nbd: Remove kernel internal header
Documentation: nbd: Add list of module parameters
Documentation: nbd: Reformat to allow more documentation
NVMe: increase depth of admin queue
nvme: Fix PRP list calculation for non-4k system page size
NVMe: Fix blk-mq hot cpu notification
NVMe: embedded iod mask cleanup
NVMe: Freeze admin queue on device failure
...
This adds support for the extended metadata formats through the submit
IO ioctl, and simplifies the rest when using a separate metadata format.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Checking fails static analysis due to additional arithmetic prior to
the NULL check. Mapping doesn't return NULL here anyway, so removing
the check.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
class_create() returns ERR_PTR on failure,
so IS_ERR() should be used instead of check for NULL.
Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Usually the admin queue depth of 64 is plenty, but for some use cases we
really need it larger. Examples are use cases like MAT, where you have
to touch all of NAND for init/format like purposes. In those cases, we
see a good 2x increase with an increased queue depth.
Signed-off-by: Jens Axboe <axboe@fb.com>
Acked-by: Keith Busch <keith.busch@intel.com>
PRP list calculation is supposed to be based on device's page size.
Systems with page size larger than device's page size cause corruption
to the name space as well as system memory with out this fix.
Systems like x86 might not experience this issue because it uses
PAGE_SIZE of 4K where as powerpc uses PAGE_SIZE of 64k while NVMe device's
page size varies depending upon the vendor.
Signed-off-by: Murali Iyer <mniyer@us.ibm.com>
Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Acked-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
The driver may issue commands to a device that may never return, so its
request_queue could always have active requests while the controller is
running. Waiting for the queue to freeze could block forever, which is
what blk-mq's hot cpu notification handler was doing when nvme drives
were in use.
This has the nvme driver make the asynchronous event command's tag
reserved and does not keep the request active. We can't have more than
one since the request is released back to the request_queue before the
command is completed. Having only one avoids potential tag collisions,
and reserving the tag for this purpose prevents other admin tasks from
reusing the tag.
I also couldn't think of a scenario where issuing AEN requests single
depth is worse than issuing them in batches, so I don't think we lose
anything with this change.
As an added bonus, doing it this way removes "Cancelling I/O" warnings
observed when unbinding the nvme driver from a device.
Reported-by: Yigal Korman <yigal@plexistor.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This fixes a race accessing an invalid address when a controller's admin
queue is in use during a reset for failure or hot removal occurs. The
admin queue will be frozen to prevent new users from entering prior to
the doorbell queue being unmapped.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Driver recovery requires the device's list node to have been initialized.
Fixes: https://lkml.org/lkml/2015/3/22/262
Reported-by: Steven Noonan <steven@uplinklabs.net>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Cc: Matthew Wilcox <willy@linux.intel.com>
Cc: Jens Axboe <axboe@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Keith Busch