We now wrap sbitmap waitqueues in an active counter, so we can avoid
iterating wakeups unless we have waiters there. This works as long as
everyone that's manipulating the waitqueues use the proper helpers. For
the tag wait case for shared tags, however, we add ourselves to the
waitqueue without incrementing/decrementing the ->ws_active count. This
means that wakeups can take a long time to happen.

Fix this by manually doing the inc/dec as needed for the wait queue
handling.

Reported-by: Michael Leun <kbug@newton.leun.net>
Tested-by: Michael Leun <kbug@newton.leun.net>
Cc: stable@vger.kernel.org
Reviewed-by: Omar Sandoval <osandov@fb.com>
Fixes: 5d2ee7122c73 ("sbitmap: optimize wakeup check")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

For now, blk_mq_hctx_has_pending() checks any of ctx, hctx->dispatch
or io scheduler have pending work. So, update the comment accordingly.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Expect arguments, blk_mq_put_driver_tag_hctx() and blk_mq_put_driver_tag()
is same. We can just use argument 'request' to put tag by blk_mq_put_driver_tag().
Then we can remove the unused blk_mq_put_driver_tag_hctx().

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull io_uring fixes and improvements from Jens Axboe:
 "The first five in this series are heavily inspired by the work Al did
  on the aio side to fix the races there.

  The last two re-introduce a feature that was in io_uring before it got
  merged, but which I pulled since we didn't have a good way to have
  BVEC iters that already have a stable reference. These aren't
  necessarily related to block, it's just how io_uring pins fixed
  buffers"

* tag 'io_uring-20190323' of git://git.kernel.dk/linux-block:
  block: add BIO_NO_PAGE_REF flag
  iov_iter: add ITER_BVEC_FLAG_NO_REF flag
  io_uring: mark me as the maintainer
  io_uring: retry bulk slab allocs as single allocs
  io_uring: fix poll races
  io_uring: fix fget/fput handling
  io_uring: add prepped flag
  io_uring: make io_read/write return an integer
  io_uring: use regular request ref counts

Avoid that the following warnings are reported when building with W=1:

block/blk-cgroup.c:1755: warning: Function parameter or member 'q' not described in 'blkcg_schedule_throttle'
block/blk-cgroup.c:1755: warning: Function parameter or member 'use_memdelay' not described in 'blkcg_schedule_throttle'
block/blk-cgroup.c:1779: warning: Function parameter or member 'blkg' not described in 'blkcg_add_delay'
block/blk-cgroup.c:1779: warning: Function parameter or member 'now' not described in 'blkcg_add_delay'
block/blk-cgroup.c:1779: warning: Function parameter or member 'delta' not described in 'blkcg_add_delay'

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This patch avoids that the following warning is reported when building
with W=1:

block/blk-iolatency.c:734:5: warning: no previous prototype for 'blk_iolatency_init' [-Wmissing-prototypes]

Cc: Josef Bacik <jbacik@fb.com>
Fixes: d70675121546 ("block: introduce blk-iolatency io controller") # v4.19
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

This function is not used outside the block layer core. Hence unexport it.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

For q->poll_nsec == -1, means doing classic poll, not hybrid poll.
We introduce a new flag BLK_MQ_POLL_CLASSIC to replace -1, which
may make code much easier to read.

Additionally, since val is an int obtained with kstrtoint(), val can be
a negative value other than -1, so return -EINVAL for that case.

Thanks to Damien Le Moal for some good suggestion.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

If bio_iov_iter_get_pages() is called on an iov_iter that is flagged
with NO_REF, then we don't need to add a page reference for the pages
that we add.

Add BIO_NO_PAGE_REF to track this in the bio, so IO completion knows
not to drop a reference to these pages.

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

Let blk_mq_mark_tag_wait() use the blk_mq_sched_mark_restart_hctx()
to set BLK_MQ_S_SCHED_RESTART.

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>