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>

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>

Replace the blk_poll interface that requires the caller to keep a queue
and cookie from the submissions with polling based on the bio.

Polling for the bio itself leads to a few advantages:

 - the cookie construction can made entirely private in blk-mq.c
 - the caller does not need to remember the request_queue and cookie
   separately and thus sidesteps their lifetime issues
 - keeping the device and the cookie inside the bio allows to trivially
   support polling BIOs remapping by stacking drivers
 - a lot of code to propagate the cookie back up the submission path can
   be removed entirely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Link: https://lore.kernel.org/r/20211012111226.760968-15-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

We never checked for errors on add_disk() as this function
returned void. Now that this is fixed, use the shiny new
error handling. The actual cleanup in case of error is
already handled by the caller of null_gendisk_register().

Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20210818144542.19305-12-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Move them (PAGE_SECTORS_SHIFT, PAGE_SECTORS and SECTOR_MASK) to the
generic header file to remove redundancy.

Signed-off-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Link: https://lore.kernel.org/r/20210721025315.1729118-1-guoqing.jiang@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Fix up the recent blk_alloc_disk conversion.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210614060231.3965278-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Use blk_mq_alloc_disk and blk_cleanup_disk to simplify the gendisk and
request_queue allocation.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Link: https://lore.kernel.org/r/20210602065345.355274-21-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

The error handling on a nullb->disk allocation currently jumps to
out_cleanup_disk that calls blk_cleanup_disk with a null pointer causing
a null pointer dereference issue. Fix this by jumping to out_cleanup_tags
instead.

Addresses-Coverity: ("Dereference after null check")
Fixes: 132226b301b5 ("null_blk: convert to blk_alloc_disk/blk_cleanup_disk")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210602100659.11058-1-colin.king@canonical.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Convert the null_blk driver to use the blk_alloc_disk and blk_cleanup_disk
helpers to simplify gendisk and request_queue allocation.  Note that the
blk-mq mode is left with its own allocations scheme, to be handled later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-26-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull block driver updates from Jens Axboe:

 - MD changes via Song:
        - raid5 POWER fix
        - raid1 failure fix
        - UAF fix for md cluster
        - mddev_find_or_alloc() clean up
        - Fix NULL pointer deref with external bitmap
        - Performance improvement for raid10 discard requests
        - Fix missing information of /proc/mdstat

 - rsxx const qualifier removal (Arnd)

 - Expose allocated brd pages (Calvin)

 - rnbd via Gioh Kim:
        - Change maintainer
        - Change domain address of maintainers' email
        - Add polling IO mode and document update
        - Fix memory leak and some bug detected by static code analysis
          tools
        - Code refactoring

 - Series of floppy cleanups/fixes (Denis)

 - s390 dasd fixes (Julian)

 - kerneldoc fixes (Lee)

 - null_blk double free (Lv)

 - null_blk virtual boundary addition (Max)

 - Remove xsysace driver (Michal)

 - umem driver removal (Davidlohr)

 - ataflop fixes (Dan)

 - Revalidate disk removal (Christoph)

 - Bounce buffer cleanups (Christoph)

 - Mark lightnvm as deprecated (Christoph)

 - mtip32xx init cleanups (Shixin)

 - Various fixes (Tian, Gustavo, Coly, Yang, Zhang, Zhiqiang)

* tag 'for-5.13/drivers-2021-04-27' of git://git.kernel.dk/linux-block: (143 commits)
  async_xor: increase src_offs when dropping destination page
  drivers/block/null_blk/main: Fix a double free in null_init.
  md/raid1: properly indicate failure when ending a failed write request
  md-cluster: fix use-after-free issue when removing rdev
  nvme: introduce generic per-namespace chardev
  nvme: cleanup nvme_configure_apst
  nvme: do not try to reconfigure APST when the controller is not live
  nvme: add 'kato' sysfs attribute
  nvme: sanitize KATO setting
  nvmet: avoid queuing keep-alive timer if it is disabled
  brd: expose number of allocated pages in debugfs
  ataflop: fix off by one in ataflop_probe()
  ataflop: potential out of bounds in do_format()
  drbd: Fix fall-through warnings for Clang
  block/rnbd: Use strscpy instead of strlcpy
  block/rnbd-clt-sysfs: Remove copy buffer overlap in rnbd_clt_get_path_name
  block/rnbd-clt: Remove max_segment_size
  block/rnbd-clt: Generate kobject_uevent when the rnbd device state changes
  block/rnbd-srv: Remove unused arguments of rnbd_srv_rdma_ev
  Documentation/ABI/rnbd-clt: Add description for nr_poll_queues
  ...