Provides the ability to identify DAX enabled devices in userspace.
Signed-off-by: NYigal Korman <yigal@plexistor.com>
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Acked-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently, presence of direct_access() in block_device_operations
indicates support of DAX on its block device.  Because
block_device_operations is instantiated with 'const', this DAX
capablity may not be enabled conditinally.

In preparation for supporting DAX to device-mapper devices, add
QUEUE_FLAG_DAX to request_queue flags to advertise their DAX
support.  This will allow to set the DAX capability based on how
mapped device is composed.
Signed-off-by: NToshi Kani <toshi.kani@hpe.com>
Acked-by: NDan Williams <dan.j.williams@intel.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: <linux-s390@vger.kernel.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

Add missing comparison to op in expression, which was forgotten when doing
the REQ_OP transition.

Fixes: b3d3fa51 ("btrfs: update __btrfs_map_block for REQ_OP transition")
Signed-off-by: NVincent Stehlé <vincent.stehle@intel.com>
Reviewed-by: NMike Christie <mchristi@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

For 4K LBA or very large disks, atari_partition can easily get tricked
into thinking it has found an Atari partition table.  Depending on the
data in the disk, it ends up creating partitions with awkward lengths.

We saw logs like this while playing with fio.

[5.625867] nvme2n1: AHDI p2
[5.625872] nvme2n1: p2 size 2910030523 extends beyond EOD, truncated

People has had issues with misinterpreted AHDI partition tables for a long
time, see this BSD thread from 1995, for example.

https://mail-index.netbsd.org/port-atari/1995/11/19/0001.html

Since the atari partition, according to the spec, doesn't even support
sector sizes with more than 512, a quick sanity check is reasonable to
just bail out early, before even attempting to read sector 0.
Signed-off-by: NGabriel Krisman Bertazi <krisman@linux.vnet.ibm.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch fix a spelling typo found in queue-sysfs.txt.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Commit 9a7f38c4 (cfq-iosched: Convert from jiffies to nanoseconds)
could result in charging just 1 ns to a cgroup submitting IO instead of 1
jiffie we always charged before. It is arguable what is the right amount
to change but for now lets retain the old behavior of always charging at
least one jiffie.

Fixes: 9a7f38c4Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Commit 9a7f38c4 (cfq-iosched: Convert from jiffies to nanoseconds)
broke the condition for detecting starved sync IO in
cfq_completed_request() because rq->start_time remained in jiffies but
we compared it with nanosecond values. This manifested as a regression
in bonnie++ rewrite performance because we always ended up considering
sync IO starved and thus never increased async IO queue depth.

Since rq->start_time is used in a lot of places, converting it to ns
values would be non-trivial. So just revert the condition in CFQ to use
comparison with jiffies. This will lead to suboptimal results if
cfq_fifo_expire[1] will ever come close to 1 jiffie but so far we are
relatively far from that with the storage used with CFQ (the default
value is 128 ms).

Fixes: 9a7f38c4Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

slice_resid can be both positive and negative. Commit 9a7f38c4
(cfq-iosched: Convert from jiffies to nanoseconds) converted it from
long to u64. Although this did not introduce any functional regression
(the operations just overflow and the result was fine), it is certainly
wrong and could cause issues in future. So convert the type to more
appropriate s64.

Fixes: 9a7f38c4Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Currently rq->fifo_time is unsigned long but CFQ stores nanosecond
timestamp in it which would overflow on 32-bit archs. Convert it to u64
to avoid the overflow. Since the rq->fifo_time is unioned with struct
call_single_data(), this does not change the size of struct request in
any way.

We have to slightly fixup block/deadline-iosched.c so that comparison
happens in the right types.

Fixes: 9a7f38c4Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

The blktrace code stores the current time in a 32-bit word in its
user interface. This is a bad idea because 32-bit seconds overflow
at some point.

We probably have until 2106 before this one overflows, as it seems
to use an 'unsigned' variable, but we should confirm that user
space treats it the same way.

Aside from this, we want to stop using 'struct timespec' here,
so I'm adding a comment about the overflow and change the code
to use timespec64 instead to make the loss of range more obvious.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

Detected by sparse.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch avoids that building with W=1 C=2 triggers the following
warning:

block/bio-integrity.c:35:6: warning: symbol 'blk_flush_integrity' was not declared. Should it be static?
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

A value is assigned to the variable 'info' but that value is never
used. Hence remove the variable 'info'.
Signed-off-by: NBart Van Assche <bart.vanassche@sandisk.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

No one need this macro now, so remove it. Basically
only how many bvecs in one bio matters instead
of how many bytes in this bio.

The motivation is for supporting multipage bvecs, in
which we only know what the max count of bvecs is supported
in the bio.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

If we're queuing REQ_PRIO IO and the task is running at an idle IO
class, then temporarily boost the priority. This prevents livelocks
due to priority inversion, when a low priority task is holding file
system resources while attempting to do IO.

An example of that is shown below. An ioniced idle task is holding
the directory mutex, while a normal priority task is trying to do
a directory lookup.

[478381.198925] ------------[ cut here ]------------
[478381.200315] INFO: task ionice:1168369 blocked for more than 120 seconds.
[478381.201324]       Not tainted 4.0.9-38_fbk5_hotfix1_2936_g85409c6 #1
[478381.202278] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[478381.203462] ionice          D ffff8803692736a8     0 1168369      1 0x00000080
[478381.203466]  ffff8803692736a8 ffff880399c21300 ffff880276adcc00 ffff880369273698
[478381.204589]  ffff880369273fd8 0000000000000000 7fffffffffffffff 0000000000000002
[478381.205752]  ffffffff8177d5e0 ffff8803692736c8 ffffffff8177cea7 0000000000000000
[478381.206874] Call Trace:
[478381.207253]  [<ffffffff8177d5e0>] ? bit_wait_io_timeout+0x80/0x80
[478381.208175]  [<ffffffff8177cea7>] schedule+0x37/0x90
[478381.208932]  [<ffffffff8177f5fc>] schedule_timeout+0x1dc/0x250
[478381.209805]  [<ffffffff81421c17>] ? __blk_run_queue+0x37/0x50
[478381.210706]  [<ffffffff810ca1c5>] ? ktime_get+0x45/0xb0
[478381.211489]  [<ffffffff8177c407>] io_schedule_timeout+0xa7/0x110
[478381.212402]  [<ffffffff810a8c2b>] ? prepare_to_wait+0x5b/0x90
[478381.213280]  [<ffffffff8177d616>] bit_wait_io+0x36/0x50
[478381.214063]  [<ffffffff8177d325>] __wait_on_bit+0x65/0x90
[478381.214961]  [<ffffffff8177d5e0>] ? bit_wait_io_timeout+0x80/0x80
[478381.215872]  [<ffffffff8177d47c>] out_of_line_wait_on_bit+0x7c/0x90
[478381.216806]  [<ffffffff810a89f0>] ? wake_atomic_t_function+0x40/0x40
[478381.217773]  [<ffffffff811f03aa>] __wait_on_buffer+0x2a/0x30
[478381.218641]  [<ffffffff8123c557>] ext4_bread+0x57/0x70
[478381.219425]  [<ffffffff8124498c>] __ext4_read_dirblock+0x3c/0x380
[478381.220467]  [<ffffffff8124665d>] ext4_dx_find_entry+0x7d/0x170
[478381.221357]  [<ffffffff8114c49e>] ? find_get_entry+0x1e/0xa0
[478381.222208]  [<ffffffff81246bd4>] ext4_find_entry+0x484/0x510
[478381.223090]  [<ffffffff812471a2>] ext4_lookup+0x52/0x160
[478381.223882]  [<ffffffff811c401d>] lookup_real+0x1d/0x60
[478381.224675]  [<ffffffff811c4698>] __lookup_hash+0x38/0x50
[478381.225697]  [<ffffffff817745bd>] lookup_slow+0x45/0xab
[478381.226941]  [<ffffffff811c690e>] link_path_walk+0x7ae/0x820
[478381.227880]  [<ffffffff811c6a42>] path_init+0xc2/0x430
[478381.228677]  [<ffffffff813e6e26>] ? security_file_alloc+0x16/0x20
[478381.229776]  [<ffffffff811c8c57>] path_openat+0x77/0x620
[478381.230767]  [<ffffffff81185c6e>] ? page_add_file_rmap+0x2e/0x70
[478381.232019]  [<ffffffff811cb253>] do_filp_open+0x43/0xa0
[478381.233016]  [<ffffffff8108c4a9>] ? creds_are_invalid+0x29/0x70
[478381.234072]  [<ffffffff811c0cb0>] do_open_execat+0x70/0x170
[478381.235039]  [<ffffffff811c1bf8>] do_execveat_common.isra.36+0x1b8/0x6e0
[478381.236051]  [<ffffffff811c214c>] do_execve+0x2c/0x30
[478381.236809]  [<ffffffff811ca392>] ? getname+0x12/0x20
[478381.237564]  [<ffffffff811c23be>] SyS_execve+0x2e/0x40
[478381.238338]  [<ffffffff81780a1d>] stub_execve+0x6d/0xa0
[478381.239126] ------------[ cut here ]------------
[478381.239915] ------------[ cut here ]------------
[478381.240606] INFO: task python2.7:1168375 blocked for more than 120 seconds.
[478381.242673]       Not tainted 4.0.9-38_fbk5_hotfix1_2936_g85409c6 #1
[478381.243653] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[478381.244902] python2.7       D ffff88005cf8fb98     0 1168375 1168248 0x00000080
[478381.244904]  ffff88005cf8fb98 ffff88016c1f0980 ffffffff81c134c0 ffff88016c1f11a0
[478381.246023]  ffff88005cf8ffd8 ffff880466cd0cbc ffff88016c1f0980 00000000ffffffff
[478381.247138]  ffff880466cd0cc0 ffff88005cf8fbb8 ffffffff8177cea7 ffff88005cf8fcc8
[478381.248252] Call Trace:
[478381.248630]  [<ffffffff8177cea7>] schedule+0x37/0x90
[478381.249382]  [<ffffffff8177d08e>] schedule_preempt_disabled+0xe/0x10
[478381.250465]  [<ffffffff8177e892>] __mutex_lock_slowpath+0x92/0x100
[478381.251409]  [<ffffffff8177e91b>] mutex_lock+0x1b/0x2f
[478381.252199]  [<ffffffff817745ae>] lookup_slow+0x36/0xab
[478381.253023]  [<ffffffff811c690e>] link_path_walk+0x7ae/0x820
[478381.253877]  [<ffffffff811aeb41>] ? try_charge+0xc1/0x700
[478381.254690]  [<ffffffff811c6a42>] path_init+0xc2/0x430
[478381.255525]  [<ffffffff813e6e26>] ? security_file_alloc+0x16/0x20
[478381.256450]  [<ffffffff811c8c57>] path_openat+0x77/0x620
[478381.257256]  [<ffffffff8115b2fb>] ? lru_cache_add_active_or_unevictable+0x2b/0xa0
[478381.258390]  [<ffffffff8117b623>] ? handle_mm_fault+0x13f3/0x1720
[478381.259309]  [<ffffffff811cb253>] do_filp_open+0x43/0xa0
[478381.260139]  [<ffffffff811d7ae2>] ? __alloc_fd+0x42/0x120
[478381.260962]  [<ffffffff811b95ac>] do_sys_open+0x13c/0x230
[478381.261779]  [<ffffffff81011393>] ? syscall_trace_enter_phase1+0x113/0x170
[478381.262851]  [<ffffffff811b96c2>] SyS_open+0x22/0x30
[478381.263598]  [<ffffffff81780532>] system_call_fastpath+0x12/0x17
[478381.264551] ------------[ cut here ]------------
[478381.265377] ------------[ cut here ]------------
Signed-off-by: NJens Axboe <axboe@fb.com>
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>

Use BIO_MAX_PAGES instead and we will remove BIO_MAX_SIZE.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

No one need this macro, so remove it. The motivation is for supporting
multipage bvecs, in which we only know what the max count of bvecs is
supported in the bio, instead of max size or max sectors.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

BIO_MAX_PAGES is used as maximum count of bvecs, so
replace BIO_MAX_SECTORS with BIO_MAX_PAGES since
BIO_MAX_SECTORS is to be removed.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

bvec has one native/mature iterator for long time, so not
necessary to use the reinvented wheel for iterating bvecs
in lib/iov_iter.c.

Two ITER_BVEC test cases are run:
	- xfstest(-g auto) on loop dio/aio, no regression found
	- swap file works well under extreme stress(stress-ng --all 64 -t
	  800 -v), and lots of OOMs are triggerd, and the whole
	system still survives
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

bvec_iter_advance() only writes the parameter of iterator,
so the base address of bvec can be marked as const safely.

Without the change, we can see compiling warning in the
following patch for implementing iterate_bvec(): lib/iov_iter.c
with bvec iterator.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch moves 'struct bio_vec' and 'struct bvec_iter'
into 'include/linux/bvec.h', then always include this header
into 'include/linux/blk_types.h'.

With this change, both 'struct bvec_iter' and bvec iterator
helpers don't depend on CONFIG_BLOCK any more, then we can
use bvec iterator to implement iterate_bvec(): lib/iov_iter.c.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Suggested-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

bvec iterator helpers should be used to implement by
iterate_bvec():lib/iov_iter.c too, and move them into
one header, so that we can keep bvec iterator header
out of CONFIG_BLOCK. Then we can remove the reinventing
of wheel in iterate_bvec().
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <ming.lei@canonical.com>
Tested-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

If ->queue_rq() returns BLK_MQ_RQ_QUEUE_OK, we use continue and skip
over the rest of the loop body. However, dptr is assigned later in the
loop body, and the BLK_MQ_RQ_QUEUE_OK case is exactly the case that we'd
want it for.

NVMe isn't actually using BLK_MQ_F_DEFER_ISSUE yet, nor is any other
in-tree driver, but if the code's going to be there, it might as well
work.

Fixes: 74c45052 ("blk-mq: add a 'list' parameter to ->queue_rq()")
Signed-off-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Keep the 32-bit CPU and cmd_type flags together to avoid holes on 64-bit
architectures.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@fb.com>

This was missed from my last patchset.

This patch has ext4 crypto code use the bio op helper
to set the operation. The operation (discard, write, writesame,
etc) is now defined seperately from the other REQ bits. They
still share the bi_rw field to save space, so we use these
helpers so modules do not have to worry about setting/overwriting
info.

Jens, I am not sure how you handle patches on top of patches
in the next branches. If you merge patches that fix issues
in previous patches in next, then this patch could be part
of

commit 95fe6c1a
Author: Mike Christie <mchristi@redhat.com>
Date:   Sun Jun 5 14:31:48 2016 -0500

    block, fs, mm, drivers: use bio set/get op accessors
Signed-off-by: NMike Christie <mchristi@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJan Kara <jack@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Expose interfaces to tune time slices of CFQ IO scheduler in
microseconds.
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

Convert all time-keeping in CFQ IO scheduler from jiffies to nanoseconds
so that we can later make the intervals more fine-grained than jiffies.
One jiffie is several miliseconds and even for today's rotating disks
that is a noticeable amount of time and thus we leave disk unnecessarily
idle.
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

To avoid confusion between REQ_OP_FLUSH, which is handled by
request_fn drivers, and upper layers requesting the block layer
perform a flush sequence along with possibly a WRITE, this patch
renames REQ_FLUSH to REQ_PREFLUSH.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The last patch added a REQ_OP_FLUSH for request_fn drivers
and the next patch renames REQ_FLUSH to REQ_PREFLUSH which
will be used by file systems and make_request_fn drivers so
they can send a write/flush combo.

This patch drops xen's use of REQ_FLUSH to track if it supports
REQ_OP_FLUSH requests, so REQ_FLUSH can be deleted.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJuergen Gross <kernel@pfupf.net>
Signed-off-by: NJens Axboe <axboe@fb.com>

This adds a REQ_OP_FLUSH operation that is sent to request_fn
based drivers by the block layer's flush code, instead of
sending requests with the request->cmd_flags REQ_FLUSH bit set.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch drops the compat definition of req_op where it matches
the rq_flag_bits definitions, and drops the related old and compat
code that allowed users to set either the op or flags for the operation.

We also then store the operation in the bi_rw/cmd_flags field similar
to how we used to store the bio ioprio where it sat in the upper bits
of the field.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

We don't need bi_rw to be so large on 64 bit archs, so
reduce it to unsigned int.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

In the next patch, we move drop the compat code and make
the op a separate value that is hidden in bi_rw. To give
the op and rq bits flags room to grow this moves prio to
its own field.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The block layer will set the correct READ/WRITE operation flags/fields
when creating a request, so there is not need for drivers to set the
REQ_WRITE flag.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

Have blktrace use the req/bio op accessor to get the REQ_OP.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The req operation REQ_OP is separated from the rq_flag_bits
definition. This converts the block layer drivers to
use req_op to get the op from the request struct.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch converts the is_sync helpers to use separate variables
for the operation and flags.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

This patch converts the block layer merging code to use separate variables
for the operation and flags, and to check req_op for the REQ_OP.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>

The bio and request operation and flags are going to be separate
definitions, so we cannot pass them in as a bitmap. This patch
converts the blkg_rwstat code and its caller, cfq, to pass in the
values separately.
Signed-off-by: NMike Christie <mchristi@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NJens Axboe <axboe@fb.com>