null_blk: Delete nullb.{queue_depth, nr_queues}

Since commit 8b631f9cf0b8 ("null_blk: remove the bio based I/O path"),
struct nullb members queue_depth and nr_queues are only ever written, so
delete them.

With that, null_exit_hctx() can also be deleted.

Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20240222083420.6026-1-john.g.garry@oracle.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: pass queue_limits to blk_mq_alloc_disk

Pass the queue limits directly to blk_mq_alloc_disk instead of
setting them one at a time.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20240220093248.3290292-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: remove the bio based I/O path

The bio based I/O path complicates null_blk and also make various
data structures, including the per-command one way bigger than
required for the main request based interface. As the bio-based
path is mostly used by stacking drivers and simple memory based
drivers, and brd is a good example driver for the latter there is
no need to have a bio based path in null_blk. Remove the path
to simplify the driver and make future block layer API changes
simpler by not having to deal with the complex two API setup in
null_blk.

Note that the queue_mode field in struct nullb_device is kept as
that is simpler than having two different places to check the
value and fully open coding the debugfs helpers as the existing
ones won't work without a named struct member.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Tested-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20240220093248.3290292-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: add configfs variable shared_tags

Allow setting shared_tags through configfs, which could only be set as a
module parameter. For that purpose, delay tag_set initialization from
null_init() to null_add_dev(). Refer tag_set.ops as the flag to check if
tag_set is initialized or not.

The following parameters can not be set through configfs yet:

timeout
requeue
init_hctx

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20240130042134.2463659-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: null_blk: make fault-injection dynamically configurable per device

The null_blk driver has multiple driver-specific fault injection
mechanisms. Each fault injection configuration can only be specified by a
module parameter and cannot be reconfigured without reloading the driver.
Also, each configuration is common to all devices and is initialized every
time a new device is added.

This change adds the following subdirectories for each null_blk device.

/sys/kernel/config/nullb/<disk>/timeout_inject
/sys/kernel/config/nullb/<disk>/requeue_inject
/sys/kernel/config/nullb/<disk>/init_hctx_fault_inject

Each fault injection attribute can be dynamically set per device by a
corresponding file in these directories.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Link: https://lore.kernel.org/r/20230327143733.14599-3-akinobu.mita@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: support read-only and offline zone conditions

In zoned mode, zones with write pointers can have conditions "read-only"
or "offline". In read-only condition, zones can not be written. In
offline condition, the zones can be neither written nor read. These
conditions are intended for zones with media failures, then it is
difficult to set those conditions to zones on real devices.

To test handling of zones in the conditions, add a feature to null_blk
to set up zones in read-only or offline condition. Add new configuration
attributes "zone_readonly" and "zone_offline". Write a sector to the
attribute files to specify the target zone to set the zone conditions.
For example, following command lines do it:

echo 0 > nullb1/zone_readonly
echo 524288 > nullb1/zone_offline

When the specified zones are already in read-only or offline condition,
normal empty condition is restored to the zones. These condition changes
can be done only after the null_blk device get powered, since status
area of each zone is not yet allocated before power-on.

Also improve zone condition checks to inhibit all commands for zones in
offline conditions. In same manner, inhibit write and zone management
commands for zones in read-only condition.

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20221201061036.2342206-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: add configfs variables for 2 options

Allow setting via configfs these two options:

no_sched
shared_tag_bitmap

Previously these could only be activated as module parameters.

Still missing are:

shared_tags
timeout
requeue
init_hctx

Signed-off-by: Vincent Fu <vincent.fu@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220708174943.87787-3-vincent.fu@samsung.com
[axboe: fold in nullb == NULL fix]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

treewide: Rename enum req_opf into enum req_op

The type name enum req_opf is misleading since it suggests that values of
this type include both an operation type and flags. Since values of this
type represent an operation only, change the type name into enum req_op.

Convert the enum req_op documentation into kernel-doc format. Move a few
definitions such that the enum req_op documentation occurs just above
the enum req_op definition.

The name "req_opf" was introduced by commit ef295ecf090d ("block: better op
and flags encoding").

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Damien Le Moal <damien.lemoal@wdc.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20220714180729.1065367-2-bvanassche@acm.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block: null_blk: Fix null_zone_write()

The bio and rq fields of struct nullb_cmd are now overlapping in a
union. So we cannot use a test on ->bio being non-NULL to detect the
NULL_Q_BIO queue mode. null_zone_write() use such broken test to set the
sector position of a zone append write in the command bio or request.
When the null_blk device uses the NULL_Q_MQ queue mode,
null_zone_write() wrongly end up setting the bio sector position,
resulting in the command request to be broken and random crashes
following.

Fix this by testing the device queue mode directly.

Fixes: 8ba816b23abd ("null-blk: save memory footprint for struct nullb_cmd")
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/20220602120344.1365329-1-damien.lemoal@opensource.wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null-blk: save memory footprint for struct nullb_cmd

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

null_blk: Fix handling of submit_queues and poll_queues attributes

Commit 0a593fbbc245 ("null_blk: poll queue support") introduced the poll
queue feature to null_blk. After this change, null_blk device has both
submit queues and poll queues, and null_map_queues() callback maps the
both queues for corresponding hardware contexts. The commit also added
the device configuration attribute 'poll_queues' in same manner as the
existing attribute 'submit_queues'. These attributes allow to modify the
numbers of queues. However, when the new values are stored to these
attributes, the values are just handled only for the corresponding
queue. When number of submit_queue is updated, number of poll_queue is
not counted, or vice versa. This caused inconsistent number of queues
and queue mapping and resulted in null-ptr-dereference. This failure was
observed in blktests block/029 and block/030.

To avoid the inconsistency, fix the attribute updates to care both
submit_queues and poll_queues. Introduce the helper function
nullb_update_nr_hw_queues() to handle stores to the both two attributes.
Add poll_queues field to the struct nullb_device to track the number in
same manner as submit_queues. Add two more fields prev_submit_queues and
prev_poll_queues to keep the previous values before change. In case the
block layer failed to update the nr_hw_queues, refer the previous values
in null_map_queues() to map queues in same manner as before change.

Also add poll_queues value checks in nullb_update_nr_hw_queues() and
null_validate_conf(). They ensure the poll_queues value of each device
is within the range from 1 to module parameter value of poll_queues.

Fixes: 0a593fbbc245 ("null_blk: poll queue support")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Link: https://lore.kernel.org/r/20211029103926.845635-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: poll queue support

There's currently no way to experiment with polled IO with null_blk,
which seems like an oversight. This patch adds support for polled IO.
We keep a list of issued IOs on submit, and then process that list
when mq_ops->poll() is invoked.

A new parameter is added, poll_queues. It defaults to 1 like the
submit queues, meaning we'll have 1 poll queue available.

Fixes-by: Bart Van Assche <bvanassche@acm.org>
Fixes-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/baca710d-0f2a-16e2-60bd-b105b854e0ae@kernel.dk
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: add option for managing virtual boundary

This will enable changing the virtual boundary of null blk devices. For
now, null blk devices didn't have any restriction on the scatter/gather
elements received from the block layer. Add a module parameter and a
configfs option that will control the virtual boundary. This will
enable testing the efficiency of the block layer bounce buffer in case
a suitable application will send discontiguous IO to the given device.

Initial testing with patched FIO showed the following results (64 jobs,
128 iodepth, 1 nullb device):
IO size READ (virt=false) READ (virt=true) Write (virt=false) Write (virt=true)
---------- ------------------- ----------------- ------------------- -------------------
1k 10.7M 8482k 10.8M 8471k
2k 10.4M 8266k 10.4M 8271k
4k 10.4M 8274k 10.3M 8226k
8k 10.2M 8131k 9800k 7933k
16k 9567k 7764k 8081k 6828k
32k 8865k 7309k 5570k 5153k
64k 7695k 6586k 2682k 2617k
128k 5346k 5489k 1320k 1296k

Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Link: https://lore.kernel.org/r/20210412095523.278632-1-mgurtovoy@nvidia.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: fix command timeout completion handling

Memory backed or zoned null block devices may generate actual request
timeout errors due to the submission path being blocked on memory
allocation or zone locking. Unlike fake timeouts or injected timeouts,
the request submission path will call blk_mq_complete_request() or
blk_mq_end_request() for these real timeout errors, causing a double
completion and use after free situation as the block layer timeout
handler executes blk_mq_rq_timed_out() and __blk_mq_free_request() in
blk_mq_check_expired(). This problem often triggers a NULL pointer
dereference such as:

BUG: kernel NULL pointer dereference, address: 0000000000000050
RIP: 0010:blk_mq_sched_mark_restart_hctx+0x5/0x20
...
Call Trace:
dd_finish_request+0x56/0x80
blk_mq_free_request+0x37/0x130
null_handle_cmd+0xbf/0x250 [null_blk]
? null_queue_rq+0x67/0xd0 [null_blk]
blk_mq_dispatch_rq_list+0x122/0x850
__blk_mq_do_dispatch_sched+0xbb/0x2c0
__blk_mq_sched_dispatch_requests+0x13d/0x190
blk_mq_sched_dispatch_requests+0x30/0x60
__blk_mq_run_hw_queue+0x49/0x90
process_one_work+0x26c/0x580
worker_thread+0x55/0x3c0
? process_one_work+0x580/0x580
kthread+0x134/0x150
? kthread_create_worker_on_cpu+0x70/0x70
ret_from_fork+0x1f/0x30

This problem very often triggers when running the full btrfs xfstests
on a memory-backed zoned null block device in a VM with limited amount
of memory.

Avoid this by executing blk_mq_complete_request() in null_timeout_rq()
only for commands that are marked for a fake timeout completion using
the fake_timeout boolean in struct null_cmd. For timeout errors injected
through debugfs, the timeout handler will execute
blk_mq_complete_request()i as before. This is safe as the submission
path does not execute complete requests in this case.

In null_timeout_rq(), also make sure to set the command error field to
BLK_STS_TIMEOUT and to propagate this error through to the request
completion.

Reported-by: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Tested-by: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Reviewed-by: Johannes Thumshirn <Johannes.Thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20210331225244.126426-1-damien.lemoal@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

null_blk: Move driver into its own directory

Move null_blk driver code into the new sub-directory
drivers/block/null_blk.

Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>