Unregister sync_thread doesn't need to hold reconfig_mutex since it
doesn't reconfigure array.

And it could cause deadlock problem for raid5 as follows:

1. process A tried to reap sync thread with reconfig_mutex held after echo
   idle to sync_action.
2. raid5 sync thread was blocked if there were too many active stripes.
3. SB_CHANGE_PENDING was set (because of write IO comes from upper layer)
   which causes the number of active stripes can't be decreased.
4. SB_CHANGE_PENDING can't be cleared since md_check_recovery was not able
   to hold reconfig_mutex.

More details in the link:
https://lore.kernel.org/linux-raid/5ed54ffc-ce82-bf66-4eff-390cb23bc1ac@molgen.mpg.de/T/#t

And add one parameter to md_reap_sync_thread since it could be called by
dm-raid which doesn't hold reconfig_mutex.
Reported-and-tested-by: Donald Buczek <buczek@molgen.mpg.de>
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
Signed-off-by: Song Liu <song@kernel.org>

Spelling mistake (triple letters) in comment.
Detected with the help of Coccinelle.
Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Link: https://lore.kernel.org/r/20220521111145.81697-28-Julia.Lawall@inria.frSigned-off-by: Jens Axboe <axboe@kernel.dk>

Pull NVMe updates from Christoph:

"nvme updates for Linux 5.19

 - set non-mdts limits in nvme_scan_work (Chaitanya Kulkarni)
 - add support for TP4084 - Time-to-Ready Enhancements (me)"

* tag 'nvme-5.19-2022-05-19' of git://git.infradead.org/nvme:
  nvme: set non-mdts limits in nvme_scan_work
  nvme: add support for TP4084 - Time-to-Ready Enhancements

In current implementation we set the non-mdts limits by calling
nvme_init_non_mdts_limits() from nvme_init_ctrl_finish().
This also tries to set the limits for the discovery controller which
has no I/O queues resulting in the warning message reported by the
nvme_log_error() when running blktest nvme/002: -

[ 2005.155946] run blktests nvme/002 at 2022-04-09 16:57:47
[ 2005.192223] loop: module loaded
[ 2005.196429] nvmet: adding nsid 1 to subsystem blktests-subsystem-0
[ 2005.200334] nvmet: adding nsid 1 to subsystem blktests-subsystem-1

<------------------------------SNIP---------------------------------->

[ 2008.958108] nvmet: adding nsid 1 to subsystem blktests-subsystem-997
[ 2008.962082] nvmet: adding nsid 1 to subsystem blktests-subsystem-998
[ 2008.966102] nvmet: adding nsid 1 to subsystem blktests-subsystem-999
[ 2008.973132] nvmet: creating discovery controller 1 for subsystem nqn.2014-08.org.nvmexpress.discovery for NQN testhostnqn.
*[ 2008.973196] nvme1: Identify(0x6), Invalid Field in Command (sct 0x0 / sc 0x2) MORE DNR*
[ 2008.974595] nvme nvme1: new ctrl: "nqn.2014-08.org.nvmexpress.discovery"
[ 2009.103248] nvme nvme1: Removing ctrl: NQN "nqn.2014-08.org.nvmexpress.discovery"

Move the call of nvme_init_non_mdts_limits() to nvme_scan_work() after
we verify that I/O queues are created since that is a converging point
for each transport where these limits are actually used.

1. FC :
nvme_fc_create_association()
 ...
 nvme_fc_create_io_queues(ctrl);
 ...
 nvme_start_ctrl()
  nvme_scan_queue()
   nvme_scan_work()

2. PCIe:-
nvme_reset_work()
 ...
 nvme_setup_io_queues()
  nvme_create_io_queues()
   nvme_alloc_queue()
 ...
 nvme_start_ctrl()
  nvme_scan_queue()
   nvme_scan_work()

3. RDMA :-
nvme_rdma_setup_ctrl
 ...
  nvme_rdma_configure_io_queues
  ...
  nvme_start_ctrl()
   nvme_scan_queue()
    nvme_scan_work()

4. TCP :-
nvme_tcp_setup_ctrl
 ...
  nvme_tcp_configure_io_queues
  ...
  nvme_start_ctrl()
   nvme_scan_queue()
    nvme_scan_work()

* nvme_scan_work()
...
nvme_validate_or_alloc_ns()
  nvme_alloc_ns()
   nvme_update_ns_info()
    nvme_update_disk_info()
     nvme_config_discard() <---
     blk_queue_max_write_zeroes_sectors() <---
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Add support for using longer timeouts during controller initialization
and letting the controller come up with namespaces that are not ready
for I/O yet.  We skip these not ready namespaces during scanning and
only bring them online once anoter scan is kicked off by the AEN that
is set when the NRDY bit gets set in the  I/O Command Set Independent
Identify Namespace Data Structure.   This asynchronous probing avoids
blocking the kernel boot when controllers take a very long time to
recover after unclean shutdowns (up to minutes).
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>

Pull NVMe updates from Christoph:

"nvme updates for Linux 5.19

 - tighten the PCI presence check (Stefan Roese):
 - fix a potential NULL pointer dereference in an error path
   (Kyle Miller Smith)
 - fix interpretation of the DMRSL field (Tom Yan)
 - relax the data transfer alignment (Keith Busch)
 - verbose error logging improvements (Max Gurtovoy, Chaitanya Kulkarni)
 - misc cleanups (Chaitanya Kulkarni, me)"

* tag 'nvme-5.19-2022-05-18' of git://git.infradead.org/nvme:
  nvme: split the enum used for various register constants
  nvme-fabrics: add a request timeout helper
  nvme-pci: harden drive presence detect in nvme_dev_disable()
  nvme-pci: fix a NULL pointer dereference in nvme_alloc_admin_tags
  nvme: mark internal passthru request RQF_QUIET
  nvme: remove unneeded include from constants file
  nvme: add missing status values to verbose logging
  nvme: set dma alignment to dword
  nvme: fix interpretation of DMRSL

Instead of having one big enum add one for each register or field.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

When userspace closes the socket before sending a disconnect
request, the following I/O requests will be blocked in
wait_for_reconnect() until dead timeout. This will cause the
following disconnect request also hung on blk_mq_quiesce_queue().
That means we have no way to disconnect a nbd device if there
are some I/O requests waiting for reconnecting until dead timeout.
It's not expected. So let's wake up the thread waiting for
reconnecting directly when a disconnect request is sent.
Reported-by: Xu Jianhai <zero.xu@bytedance.com>
Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Link: https://lore.kernel.org/r/20220322080639.142-1-xieyongji@bytedance.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

The RDAMA and TCP transport both complete the timed out request in the
same manner and hence code is duplicated. Add and use the helper
nvmf_complete_timed_out_request() to remove the duplicate code.
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

On our ZynqMP system we observe, that a NVMe drive that resets itself
while doing a firmware update causes a Kernel crash like this:

[ 67.720772] pcieport 0000:02:02.0: pciehp: Slot(2): Link Down
[ 67.720783] pcieport 0000:02:02.0: pciehp: Slot(2): Card not present
[ 67.720795] nvme 0000:04:00.0: PME# disabled
[ 67.720849] Internal error: synchronous external abort: 96000010 [#1] PREEMPT SMP
[ 67.720853] nwl-pcie fd0e0000.pcie: Slave error

Analysis: When nvme_dev_disable() is called because of this PCIe hotplug
event, pci_is_enabled() is still true. And accessing the NVMe drive
which is currently not available as it's in reboot process causes this
"synchronous external abort" on this ARM64 platform.

This patch adds the pci_device_is_present() check as well, which returns
false in this "Card not present" hot-plug case. With this change, the
NVMe driver does not try to access the NVMe registers any more and the
FW update finishes without any problems.
Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

In nvme_alloc_admin_tags, the admin_q can be set to an error (typically
-ENOMEM) if the blk_mq_init_queue call fails to set up the queue, which
is checked immediately after the call. However, when we return the error
message up the stack, to nvme_reset_work the error takes us to
nvme_remove_dead_ctrl()
  nvme_dev_disable()
   nvme_suspend_queue(&dev->queues[0]).

Here, we only check that the admin_q is non-NULL, rather than not
an error or NULL, and begin quiescing a queue that never existed, leading
to bad / NULL pointer dereference.
Signed-off-by: Kyle Smith <kyles@hpe.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Most of the internal passthru commands use __nvme_submit_sync_cmd()
interface. There are few places we open code the request submission :-

1. nvme_keep_alive_work(struct work_struct *work)
2. nvme_timeout(struct request *req, bool reserved)
3. nvme_delete_queue(struct nvme_queue *nvmeq, u8 opcode)

Mark the internal passthru request quiet so that we can skip the verbose
error message from nvme_log_error() in nvme_end_req() completion path,
this will be consistent with what we have in __nvme_submit_sync_cmd().
Signed-off-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Alan Adamson <alan.adamson@oracle.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

No usage of blkdev.h elements.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Log a few more path related status codes.
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>

The nvme specification only requires qword alignment for segment
descriptors, and the driver already guarantees that. The spec has always
allowed user data to be dword aligned, which is what the queue's
attribute is for, so relax the alignment requirement to that value.

While we could allow byte alignment for some controllers when using
SGLs, we still need to support PRP, and that only allows dword.

Fixes: 3b2a1ebc ("nvme: set dma alignment to qword")
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

DMRSLl is in the unit of logical blocks, while max_discard_sectors is
in the unit of "linux sector".
Signed-off-by: Tom Yan <tom.ty89@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Just leave the SPDX marker and the copyright notice and remove the
irrelevant rest.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220419063303.583106-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Remove the irrelevant changelogs and todo notes and just leave the SPDX
marker and the copyright notice.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220419063303.583106-4-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The copyright statement says:

"Redistribution of this file is permitted under the GNU General Public
 License." and was added by Ted in 1993, at which point GPLv2 only
 was the default Linux license.

Replace it with the usual GPLv2 only SPDX header.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220419063303.583106-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Merge loop.h into loop.c as all the content is only used there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220419063303.583106-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Currently, the directory name used to create a nullb device through
sysfs is not used as the device name, potentially causing headaches for
users if devices are already created through the modprobe operation
withe the nr_device module parameter not set to 0. E.g. a user can do
"mkdir /sys/kernel/config/nullb/nullb0" to create a nullb device even
though /dev/nullb0 was already created by modprobe. In this case, the
configfs nullb device will be named nullb1, causing confusion for the
user.

Simplify this by using the configfs directory name as the nullb device
name, always, unless another nullb device is already using the same
name. E.g. if modprobe created nullb0, then:

$ mkdir /sys/kernel/config/nullb/nullb0
mkdir: cannot create directory '/sys/kernel/config/nullb/nullb0': File
exists

will be reported to the user.

To implement this, the function null_find_dev_by_name() is added to
check for the existence of a nullb device with the name used for a new
configfs device directory. nullb_group_make_item() uses this new
function to check if the directory name can be used as the disk name.
Finally, null_add_dev() is modified to use the device config item name
as the disk name for a new nullb device created using configfs.
The naming of devices created though modprobe remains unchanged.

Of note is that it is possible for a user to create through configfs a
nullb device with the same name as an existing device. E.g.

$ mkdir /sys/kernel/config/nullb/null

will successfully create the nullb device named "null" but this block
device will however not appear under /dev/ since /dev/null already
exists.
Suggested-by: Joseph Bacik <josef@toxicpanda.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20220420005718.3780004-5-damien.lemoal@opensource.wdc.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

Use the pr_fmt() macro to prefix all null_blk pr_xxx() messages with
"null_blk:" to clarify which module is printing the messages. Also add
a pr_info() message in null_add_dev() to print the name of a newly
created disk.
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20220420005718.3780004-4-damien.lemoal@opensource.wdc.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

Introduce the null_create_dev() and null_destroy_dev() helper functions
to respectivel create nullb devices on modprobe and destroy them on
rmmod. The null_destroy_dev() helper avoids duplicated code in the
null_init() and null_exit() functions for deleting devices.
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20220420005718.3780004-3-damien.lemoal@opensource.wdc.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

Fix message grammar and code style issues (brackets and indentation) in
null_init().
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20220420005718.3780004-2-damien.lemoal@opensource.wdc.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

Use bdev_discard_alignment to calculate the correct discard alignment
offset even for partitions instead of just looking at the queue limit.

Also switch to use bdev_discard_granularity to get rid of the last direct
queue reference in xen_blkbk_discard.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-12-hch@lst.de
[axboe: fold in 'q' removal as it's now unused]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use bdev_discard_alignment to calculate the correct discard alignment
offset even for partitions instead of just looking at the queue limit.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-11-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The nvme driver never sets a discard_alignment, so it also doens't need
to clear it to zero.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-10-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The loop driver never sets a discard_alignment, so it also doens't need
to clear it to zero.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-9-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
Setting it to PAGE_SIZE while the discard granularity is the block size
that is smaller or the same as PAGE_SIZE as done by dasd is mostly
harmless but also useless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
Setting it to the discard granularity as done by raid5 is mostly
harmless but also useless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-7-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
Setting it to the discard granularity as done by dm-zoned is mostly
harmless but also useless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-6-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.

On the other hand the discard_sector_alignment from the virtio 1.1 looks
similar to what Linux uses as discard granularity (even if not very well
described):

  "discard_sector_alignment can be used by OS when splitting a request
   based on alignment. "

And at least qemu does set it to the discard granularity.

So stop setting the discard_alignment and use the virtio
discard_sector_alignment to set the discard granularity.

Fixes: 1f23816b ("virtio_blk: add discard and write zeroes support")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-5-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
Setting it to the discard granularity as done by null_blk is mostly
harmless but also useless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-4-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
Setting it to the discard granularity as done by nbd is mostly harmless
but also useless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

The discard_alignment queue limit is named a bit misleading means the
offset into the block device at which the discard granularity starts.
Setting it to the discard granularity as done by ubd is mostly harmless
but also useless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220418045314.360785-2-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

Flushing system-wide workqueues is dangerous and will be forbidden.
Replace system_wq with local aoe_wq.

Link: https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@I-love.SAKURA.ne.jpSigned-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://lore.kernel.org/r/abb37616-eec9-2794-e21e-7c623085d987@I-love.SAKURA.ne.jpSigned-off-by: Jens Axboe <axboe@kernel.dk>

Merge branch 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md into for-5.19/drivers

Pull MD updates from Song:

"1. Improve annotation in raid5 code, by Logan Gunthorpe.
 2. Support MD_BROKEN flag in raid-1/5/10, by Mariusz Tkaczyk.
 3. Other small fixes/cleanups."

* 'md-next' of https://git.kernel.org/pub/scm/linux/kernel/git/song/md:
  md: Replace role magic numbers with defined constants
  md/raid0: Ignore RAID0 layout if the second zone has only one device
  md/raid5: Annotate functions that hold device_lock with __must_hold
  md/raid5-ppl: Annotate with rcu_dereference_protected()
  md/raid5: Annotate rdev/replacement access when mddev_lock is held
  md/raid5: Annotate rdev/replacement accesses when nr_pending is elevated
  md/raid5: Add __rcu annotation to struct disk_info
  md/raid5: Un-nest struct raid5_percpu definition
  md/raid5: Cleanup setup_conf() error returns
  md: replace deprecated strlcpy & remove duplicated line
  md/bitmap: don't set sb values if can't pass sanity check
  md: fix an incorrect NULL check in md_reload_sb
  md: fix an incorrect NULL check in does_sb_need_changing
  raid5: introduce MD_BROKEN
  md: Set MD_BROKEN for RAID1 and RAID10

Total 16 bytes can be saved in two ways:

1) The field 'bio' will only be used in bio based mode, and the field
   'rq' will only be used in mq mode. Since they won't be used in the
   same time, declare a union for them.
2) The field 'bool fake_timeout' can be placed in the hole after the
   field 'error'.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Link: https://lore.kernel.org/r/20220426022133.3999006-1-yukuai3@huawei.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

There are several instances where magic numbers are used in md.c instead
of the defined constants in md_p.h. This patch set improves code
readability by replacing all occurrences of 0xffff, 0xfffe, and 0xfffd when
relating to md roles with their equivalent defined constant.
Signed-off-by: David Sloan <david.sloan@eideticom.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Song Liu <song@kernel.org>

The RAID0 layout is irrelevant if all members have the same size so the
array has only one zone. It is *also* irrelevant if the array has two
zones and the second zone has only one device, for example if the array
has two members of different sizes.

So in that case it makes sense to allow assembly even when the layout is
undefined, like what is done when the array has only one zone.
Reviewed-by: NeilBrown <neilb@suse.de>
Signed-off-by: Pascal Hambourg <pascal@plouf.fr.eu.org>
Signed-off-by: Song Liu <song@kernel.org>