We cannot detect a (perhaps buggy) controller that is sending us
a completion for a request that was already completed (for example
sending a completion twice), this phenomenon was seen in the wild
a few times.

So to protect against this, we use the upper 4 msbits of the nvme sqe
command_id to use as a 4-bit generation counter and verify it matches
the existing request generation that is incrementing on every execution.

The 16-bit command_id structure now is constructed by:
| xxxx | xxxxxxxxxxxx |
  gen    request tag

This means that we are giving up some possible queue depth as 12 bits
allow for a maximum queue depth of 4095 instead of 65536, however we
never create such long queues anyways so no real harm done.

Suggested-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Acked-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Tested-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

We already validate it when receiving the c2hdata pdu header
and this is not changing so this is a redundant check.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

We are going to use the upper 4-bits of the command_id for a generation
counter, so enforce the new queue depth upper limit. As we enforce
both min and max queue depth, use param_set_uint_minmax istead of
open coding it.

Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

It is a useful helper hence move it to common code so others can enjoy
it.

Suggested-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Lightnvm supports the OCSSD 1.x and 2.0 specs which were early attempts
to produce Open Channel SSDs and never made it into the NVMe spec
proper.  They have since been superceeded by NVMe enhancements such
as ZNS support.  Remove the support per the deprecation schedule.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210812132308.38486-1-hch@lst.de


Reviewed-by: Matias Bjørling <mb@lightnvm.io>
Reviewed-by: Javier González <javier@javigon.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

nbd_index_mutex is currently held over add_disk and inside ->open, which
leads to lock order reversals.  Refactor the device creation code path
so that nbd_dev_add is called without nbd_index_mutex lock held and
only takes it for the IDR insertation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-7-hch@lst.de


[axboe: fix whitespace]
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use idr_for_each_entry instead of the awkward callback to find an
existing device for the index == -1 case, and de-duplicate the device
allocation if no existing device was found.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-6-hch@lst.de


Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Return the device we just allocated instead of doing an extra search for
it in the caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-5-hch@lst.de


Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Fold nbd_del_disk and remove the pointless NULL check on ->disk given
that it is always set for a successfully allocated nbd_device structure.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-4-hch@lst.de


Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Share common code for the synchronous and workqueue based device removal,
and remove the pointless use of refcount_dec_and_mutex_lock.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-3-hch@lst.de


Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now open_mutex is used to synchronize partition operations (e.g,
blk_drop_partitions() and blkdev_reread_part()), however it makes
nbd driver broken, because nbd may call del_gendisk() in nbd_release()
or nbd_genl_disconnect() if NBD_CFLAG_DESTROY_ON_DISCONNECT is enabled,
and deadlock occurs, as shown below:

// AB-BA dead-lock
nbd_genl_disconnect            blkdev_open
  nbd_disconnect_and_put
                                 lock bd_mutex
  // last ref
  nbd_put
    lock nbd_index_mutex
      del_gendisk
                                   nbd_open
                                     try lock nbd_index_mutex
        try lock bd_mutex

 or

// AA dead-lock
nbd_release
  lock bd_mutex
    nbd_put
      try lock bd_mutex

Instead of fixing block layer (e.g, introduce another lock), fixing
the nbd driver to call del_gendisk() in a kworker when
NBD_DESTROY_ON_DISCONNECT is enabled. When NBD_DESTROY_ON_DISCONNECT
is disabled, nbd device will always be destroy through module removal,
and there is no risky of deadlock.

To ensure the reuse of nbd index succeeds, moving the calling of
idr_remove() after del_gendisk(), so if the reused index is not found
in nbd_index_idr, the old disk must have been deleted. And reusing
the existing destroy_complete mechanism to ensure nbd_genl_connect()
will wait for the completion of del_gendisk().

Also adding a new workqueue for nbd removal, so nbd_cleanup()
can ensure all removals complete before exits.

Reported-by:  <syzbot+0fe7752e52337864d29b@syzkaller.appspotmail.com>
Fixes: c76f48eb ("block: take bd_mutex around delete_partitions in del_gendisk")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210811124428.2368491-2-hch@lst.de


Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If user specify a large enough value of NBD blocks option, it may trigger
signed integer overflow which may lead to nbd->config->bytesize becomes a
large or small value, zero in particular.

UBSAN: Undefined behaviour in drivers/block/nbd.c:325:31
signed integer overflow:
1024 * 4611686155866341414 cannot be represented in type 'long long int'
[...]
Call trace:
[...]
 handle_overflow+0x188/0x1dc lib/ubsan.c:192
 __ubsan_handle_mul_overflow+0x34/0x44 lib/ubsan.c:213
 nbd_size_set drivers/block/nbd.c:325 [inline]
 __nbd_ioctl drivers/block/nbd.c:1342 [inline]
 nbd_ioctl+0x998/0xa10 drivers/block/nbd.c:1395
 __blkdev_driver_ioctl block/ioctl.c:311 [inline]
[...]

Although it is not a big deal, still silence the UBSAN by limit
the input value.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20210804021212.990223-1-libaokun1@huawei.com


[axboe: dropped unlikely()]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The variable err is being assigned a value that is never read, the
assignment is redundant and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20210806110601.11386-1-colin.king@canonical.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

sysfs_emit function was added to be aware of the PAGE_SIZE maximum of
the temporary buffer used for outputting sysfs content, so there is no
possible overruns. So replace the uses of any s*printf functions for
the sysfs show functions with sysfs_emit.

Signed-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Link: https://lore.kernel.org/r/20210726115950.470543-3-jinpu.wang@ionos.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch replaces put_cpu_var with put_cpu_ptr because
get_cpu_ptr should be paired with put_cpu_ptr.

Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Link: https://lore.kernel.org/r/20210726115950.470543-2-jinpu.wang@ionos.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

In block/blk-mq-sysfs.c, struct blk_mq_ctx_sysfs_entry is not used to
define any attribute since the "mq" sysfs directory contains only
sub-directories (no attribute files). As a result, blk_mq_sysfs_show(),
blk_mq_sysfs_store(), and struct sysfs_ops blk_mq_sysfs_ops are all
unused and unnecessary. Remove all this unused code.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210713081837.524422-1-damien.lemoal@wdc.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Make the loop device raise a DISK_MEDIA_CHANGE event on attach or detach.

	# udevadm monitor -up |grep -e DISK_MEDIA_CHANGE -e DEVNAME &

	# losetup -f zero
	[    7.454235] loop0: detected capacity change from 0 to 16384
	DISK_MEDIA_CHANGE=1
	DEVNAME=/dev/loop0
	DEVNAME=/dev/loop0
	DEVNAME=/dev/loop0

	# losetup -f zero
	[   10.205245] loop1: detected capacity change from 0 to 16384
	DISK_MEDIA_CHANGE=1
	DEVNAME=/dev/loop1
	DEVNAME=/dev/loop1
	DEVNAME=/dev/loop1

	# losetup -f zero2
	[   13.532368] loop2: detected capacity change from 0 to 40960
	DISK_MEDIA_CHANGE=1
	DEVNAME=/dev/loop2
	DEVNAME=/dev/loop2

	# losetup -D
	DEVNAME=/dev/loop1
	DISK_MEDIA_CHANGE=1
	DEVNAME=/dev/loop1
	DEVNAME=/dev/loop2
	DISK_MEDIA_CHANGE=1
	DEVNAME=/dev/loop2
	DEVNAME=/dev/loop0
	DISK_MEDIA_CHANGE=1
	DEVNAME=/dev/loop0

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-7-mcroce@linux.microsoft.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Refactor disk_check_events() and move some code into disk_event_uevent().
Then add disk_force_media_change(), a helper which will be used by
devices to force issuing a DISK_EVENT_MEDIA_CHANGE event.

Co-developed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-6-mcroce@linux.microsoft.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Add a new sysfs handle to export the new diskseq value.
Place it in <sysfs>/block/<disk>/diskseq and document it.

    $ grep . /sys/class/block/*/diskseq
    /sys/class/block/loop0/diskseq:13
    /sys/class/block/loop1/diskseq:14
    /sys/class/block/loop2/diskseq:5
    /sys/class/block/loop3/diskseq:6
    /sys/class/block/ram0/diskseq:1
    /sys/class/block/ram1/diskseq:2
    /sys/class/block/vda/diskseq:7

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-5-mcroce@linux.microsoft.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Add a new BLKGETDISKSEQ ioctl which retrieves the disk sequence number
from the genhd structure.

    # ./getdiskseq /dev/loop*
    /dev/loop0:     13
    /dev/loop0p1:   13
    /dev/loop0p2:   13
    /dev/loop0p3:   13
    /dev/loop1:     14
    /dev/loop1p1:   14
    /dev/loop1p2:   14
    /dev/loop2:     5
    /dev/loop3:     6

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-4-mcroce@linux.microsoft.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Export the newly introduced diskseq in uevents:

    $ udevadm info /sys/class/block/* |grep -e DEVNAME -e DISKSEQ
    E: DEVNAME=/dev/loop0
    E: DISKSEQ=1
    E: DEVNAME=/dev/loop1
    E: DISKSEQ=2
    E: DEVNAME=/dev/loop2
    E: DISKSEQ=3
    E: DEVNAME=/dev/loop3
    E: DISKSEQ=4
    E: DEVNAME=/dev/loop4
    E: DISKSEQ=5
    E: DEVNAME=/dev/loop5
    E: DISKSEQ=6
    E: DEVNAME=/dev/loop6
    E: DISKSEQ=7
    E: DEVNAME=/dev/loop7
    E: DISKSEQ=8
    E: DEVNAME=/dev/nvme0n1
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p1
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p2
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p3
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p4
    E: DISKSEQ=9
    E: DEVNAME=/dev/nvme0n1p5
    E: DISKSEQ=9
    E: DEVNAME=/dev/sda
    E: DISKSEQ=10
    E: DEVNAME=/dev/sda1
    E: DISKSEQ=10
    E: DEVNAME=/dev/sda2
    E: DISKSEQ=10

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-3-mcroce@linux.microsoft.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Associating uevents with block devices in userspace is difficult and racy:
the uevent netlink socket is lossy, and on slow and overloaded systems
has a very high latency.
Block devices do not have exclusive owners in userspace, any process can
set one up (e.g. loop devices). Moreover, device names can be reused
(e.g. loop0 can be reused again and again). A userspace process setting
up a block device and watching for its events cannot thus reliably tell
whether an event relates to the device it just set up or another earlier
instance with the same name.

Being able to set a UUID on a loop device would solve the race conditions.
But it does not allow to derive orderings from uevents: if you see a
uevent with a UUID that does not match the device you are waiting for,
you cannot tell whether it's because the right uevent has not arrived yet,
or it was already sent and you missed it. So you cannot tell whether you
should wait for it or not.

Associating a unique, monotonically increasing sequential number to the
lifetime of each block device, which can be retrieved with an ioctl
immediately upon setting it up, allows to solve the race conditions with
uevents, and also allows userspace processes to know whether they should
wait for the uevent they need or if it was dropped and thus they should
move on.

Additionally, increment the disk sequence number when the media change,
i.e. on DISK_EVENT_MEDIA_CHANGE event.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matteo Croce <mcroce@microsoft.com>
Tested-by: Luca Boccassi <bluca@debian.org>
Link: https://lore.kernel.org/r/20210712230530.29323-2-mcroce@linux.microsoft.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>

cmdline-parser.c is only used by the cmdline faux partition format,
so merge the code into that and avoid an indirect call.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210728053756.409654-1-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Remove the disk_name function now that all users are gone.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-7-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

disk_name for partition 0 just copies out the disk_name field.  Replace
the call to disk_name with a %s format specifier.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-6-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Printk ->disk_name directly for the disk and use the %pg format specifier
for the block device, which is equivalent to a bdevname call.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-5-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Simplify printing the partition name by using the %pg format specifier
that is equivalent to a bdevname call.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-4-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Simplify printing the partition name by using the %pg format specifier
that is equivalent to a bdevname call.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-3-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

I have compiled the kernel with a cross compiler "hppa-linux-gnu-" v9.3.0
on x86-64 host machine. I got the following warning:

block/genhd.c: In function ‘diskstats_show’:
block/genhd.c:1227:1: warning: the frame size of 1688 bytes is larger
than 1280 bytes [-Wframe-larger-than=]
 1227  |  }

By Reduced the stack footprint by using the %pg printk specifier instead
of disk_name to remove the need for the on-stack buffer.

Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727062518.122108-2-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Now that we've stopped using inode references for anything meaninful
in the block layer get rid of the helper to put it and just open code
the call to iput on the block_device inode.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Chaitanya Kulkarni <ckulkarnilinux@gmail.com>
Link: https://lore.kernel.org/r/20210722075402.983367-10-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

All callers are gone, and no one should grab a pure inode reference to
a block device anymore.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20210722075402.983367-9-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

The whole device block device won't be removed while the disk is still
alive, so don't bother to grab a reference to it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Ming Lei <ming.lei@rehat.com>
Reviewed-by: Chaitanya Kulkarni <ckulkarnilinux@gmail.com>
Link: https://lore.kernel.org/r/20210722075402.983367-8-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Instead of acquiring an inode reference on open make sure partitions
always hold device model references to the disk while alive, and switch
open to grab only a device model reference to the opened block device.
If that is a partition the disk reference is transitively held by the
partition already.

Link: https://lore.kernel.org/r/20210722075402.983367-6-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Move the allocation of bd_meta_info after initializing the struct device
to avoid the special bdput error handling path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210722075402.983367-5-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Unhash the whole device inode early in del_gendisk.  This allows to
remove the first GENHD_FL_UP check in the open path as we simply
won't find a just removed inode.  The second non-racy check after
taking open_mutex is still kept.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210722075402.983367-4-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Add a lockdep assert instead of the outdated locking comment.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Chaitanya Kulkarni <ckulkarnilinux@gmail.com>
Link: https://lore.kernel.org/r/20210722075402.983367-3-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Using local kmaps slightly reduces the chances to stray writes, and
the bvec interface cleans up the code a little bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727055646.118787-16-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Using local kmaps slightly reduces the chances to stray writes, and
the bvec interface cleans up the code a little bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727055646.118787-15-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Rewrite the actual bounce buffering loop in __blk_queue_bounce to that
the memcpy_to_bvec helper can be used to perform the data copies.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727055646.118787-14-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use memcpy_from_bvec instead of open coding the logic.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20210727055646.118787-13-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>