Except for blk_queue_split(), bio_split() is used for splitting bio too,
then the remained bio is often resubmit to queue via generic_make_request().
So the same queue enter recursion exits in this case too. Unfortunatley
commit cd4a4ae4 doesn't help this case.

This patch covers the above case by setting BIO_QUEUE_ENTERED before calling
q->make_request_fn.

In theory the per-bio flag is used to simulate one stack variable, it is
just fine to clear it after q->make_request_fn is returned. Especially
the same bio can't be submitted from another context.

Fixes: cd4a4ae4 ("block: don't use blocking queue entered for recursive bio submits")
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: NeilBrown <neilb@suse.com>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Commit 5f0ed774 ("block: sum requests in the plug structure") removed
the request_count parameter from block_attempt_plug_merge(), but did not
remove the associated kerneldoc comment, introducing this warning to the
docs build:

  ./block/blk-core.c:685: warning: Excess function parameter 'request_count' description in 'blk_attempt_plug_merge'

Remove the obsolete description and make things a little quieter.
Signed-off-by: NJonathan Corbet <corbet@lwn.net>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

There was some confusion about what these functions did.  Make it clear
that this is a hint for upper layers to pass to the block layer, and
that it does not guarantee that I/O will not be submitted between a
start and finish plug.
Reported-by: N"Darrick J. Wong" <darrick.wong@oracle.com>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This prevents a HIPRI bio from being submitted through a stacking
driver that does not support polling and thus won't poll for I/O
completion.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Replace blk_mq_request_issue_directly with blk_mq_try_issue_directly
in blk_insert_cloned_request and kill it as nobody uses it any more.
Signed-off-by: NJianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We want to convert to per-cpu in_flight counters.

The function part_round_stats needs the in_flight counter every jiffy, it
would be too costly to sum all the percpu variables every jiffy, so it
must be deleted. part_round_stats is used to calculate two counters -
time_in_queue and io_ticks.

time_in_queue can be calculated without part_round_stats, by adding the
duration of the I/O when the I/O ends (the value is almost as exact as the
previously calculated value, except that time for in-progress I/Os is not
counted).

io_ticks can be approximated by increasing the value when I/O is started
or ended and the jiffies value has changed. If the I/Os take less than a
jiffy, the value is as exact as the previously calculated value. If the
I/Os take more than a jiffy, io_ticks can drift behind the previously
calculated value.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

All of part_stat_* and related methods are used with preempt disabled,
so there is no need to pass cpu around to allow of them.  Just call
smp_processor_id() as needed.
Suggested-by: NJens Axboe <axboe@kernel.dk>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This was intended to support users like nvme multipath, but is just
getting in the way and adding another indirect call.
Reviewed-by: NSagi Grimberg <sagi@grimberg.me>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

I ran into a bug where after hibernation due to incompatible
backends, the block driver returned BLK_STS_NOTSUPP, with the
current message it's hard to find out what the command flags
were. Adding req->cmd_flags help make the problem easier to
diagnose.
Reviewed-by: NEduardo Valentin <eduval@amazon.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NBalbir Singh <sblbir@amzn.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we are issuing a list of requests, we know if we're at the last one.
If we fail issuing, ensure that we call ->commits_rqs() to flush any
potential previous requests.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Reviewed-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Only do it if we have requests for multiple queues in the same
plug.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This isn't exactly the same as the previous count, as it includes
requests for all devices. But that really doesn't matter, if we have
more than the threshold (16) queued up, flush it. It's not worth it
to have an expensive list loop for this.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

blk_poll() has always kept spinning until it found an IO. This is
fine for SYNC polling, since we need to find one request we have
pending, but in preparation for ASYNC polling it can be beneficial
to just check if we have any entries available or not.

Existing callers are converted to pass in 'spin == true', to retain
the old behavior.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If we want to support async IO polling, then we have to allow finding
completions that aren't just for the one we are looking for. Always pass
in -1 to the mq_ops->poll() helper, and have that return how many events
were found in this poll loop.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

For the synchronous I/O path case (read(), write() etc system calls), a
BIO I/O priority is not initialized until the execution of
blk_init_request_from_bio() when the BIO is submitted and a request
initialized for the BIO execution. This is due to the ki_ioprio field of
the struct kiocb defined on stack being always initialized to
IOPRIO_CLASS_NONE, regardless of the calling process I/O context ioprio
value set with ioprio_set(). This late initialization can result in the
BIO being merged to pending requests even when the I/O priorities
differ.

Fix this by initializing the ki_iopriority field of on stack struct
kiocb using the get_current_ioprio() helper, ensuring that all BIOs
allocated and submitted for the system call execution see the correct
intended I/O priority early. With this, since a BIO I/O priority is
always set to the intended effective value for both the sync and async
path, blk_init_request_from_bio() can be simplified.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NAdam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Growing in size a high priority request by merging it with a lower
priority BIO or request will increase the request execution time. This
is the opposite result of the desired effect of high I/O priorities,
namely getting low I/O latencies. Prevent merging of requests and BIOs
that have different I/O priorities to fix this.
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Define get_current_ioprio() as an inline helper to obtain the caller
I/O priority from its task I/O context. Use this helper in
blk_init_request_from_bio() to set a request ioprio.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

bio->bi_ioc is never set so always NULL. Remove references to it in
bio_disassociate_task() and in rq_ioc() and delete this field from
struct bio. With this change, rq_ioc() always returns
current->io_context without the need for a bio argument. Further
simplify the code and make it more readable by also removing this
helper, which also allows to simplify blk_mq_sched_assign_ioc() by
removing its bio argument.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: NAdam Manzanares <adam.manzanares@wdc.com>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Various spots check for q->mq_ops being non-NULL, but provide
a helper to do this instead.

Where the ->mq_ops != NULL check is redundant, remove it.

Since mq == rq-based now that legacy is gone, get rid of the
queue_is_rq_based() and just use queue_is_mq() everywhere.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

With the legacy request path gone there is no good reason to keep
queue_lock as a pointer, we can always use the embedded lock now.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

Fixed floppy and blk-cgroup missing conversions and half done edits.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

With the legacy request path gone there is no real need to override the
queue_lock.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

->queue_flags is generally not set or cleared in the fast path, and also
generally set or cleared one flag at a time.  Make use of the normal
atomic bitops for it so that we don't need to take the queue_lock,
which is otherwise mostly unused in the core block layer now.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Unused since the removal of the legacy request code.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

c2856ae2 ("blk-mq: quiesce queue before freeing queue") has
already fixed this race, however the implied synchronize_rcu()
in blk_mq_quiesce_queue() can slow down LUN probe a lot, so caused
performance regression.

Then 1311326c ("blk-mq: avoid to synchronize rcu inside blk_cleanup_queue()")
tried to quiesce queue for avoiding unnecessary synchronize_rcu()
only when queue initialization is done, because it is usual to see
lots of inexistent LUNs which need to be probed.

However, turns out it isn't safe to quiesce queue only when queue
initialization is done. Because when one SCSI command is completed,
the user of sending command can be waken up immediately, then the
scsi device may be removed, meantime the run queue in scsi_end_request()
is still in-progress, so kernel panic can be caused.

In Red Hat QE lab, there are several reports about this kind of kernel
panic triggered during kernel booting.

This patch tries to address the issue by grabing one queue usage
counter during freeing one request and the following run queue.

Fixes: 1311326c ("blk-mq: avoid to synchronize rcu inside blk_cleanup_queue()")
Cc: Andrew Jones <drjones@redhat.com>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: linux-scsi@vger.kernel.org
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: James E.J. Bottomley <jejb@linux.vnet.ibm.com>
Cc: stable <stable@vger.kernel.org>
Cc: jianchao.wang <jianchao.w.wang@oracle.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Unused now that the legacy request path is gone.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This was used for completion placement for the legacy path,
but for mq we have rq->mq_ctx->cpu for that. Add a helper
to get the request CPU assignment, as the mq_ctx type is
private to blk-mq.
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

It's now dead code, nobody uses it.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The only user of legacy timing now is BSG, which is invoked
from the mq timeout handler. Kill the legacy code, and rename
the q->rq_timed_out_fn to q->bsg_job_timeout_fn.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Now there's no difference between blk_put_request() and
__blk_put_request() anymore, get rid of the underscore version and
convert the few callers.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This removes a bunch of core and elevator related code. On the core
front, we remove anything related to queue running, draining,
initialization, plugging, and congestions. We also kill anything
related to request allocation, merging, retrieval, and completion.

Remove any checking for single queue IO schedulers, as they no
longer exist. This means we can also delete a bunch of code related
to request issue, adding, completion, etc - and all the SQ related
ops and helpers.

Also kill the load_default_modules(), as all that did was provide
for a way to load the default single queue elevator.
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

It's now unused, kill it.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Nobody is using the legacy path for blk_lld_busy() anymore, remove
it.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We'll hook into this from blk_lld_busy(), allowing blk-mq to also
return whether or not a given queue currently has requests in
progress.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Tested-by: NMing Lei <ming.lei@redhat.com>
Reviewed-by: NOmar Sandoval <osandov@fb.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This reverts a series committed earlier due to null pointer exception
bug report in [1]. It seems there are edge case interactions that I did
not consider and will need some time to understand what causes the
adverse interactions.

The original series can be found in [2] with a follow up series in [3].

[1] https://www.spinics.net/lists/cgroups/msg20719.html
[2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@gmail.com/
[3] https://lore.kernel.org/lkml/20181020185612.51587-1-dennis@kernel.org/

This reverts the following commits:
d459d853, b2c3fa54, 101246ec, b3b9f24f, e2b09899,
f0fcb3ec, c839e7a0, bdc24917, 74b7c02a, 5bf9a1f3,
a7b39b4e, 07b05bcc, 49f4c2dc, 27e6fa99Signed-off-by: NDennis Zhou <dennis@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

rq_qos_exit() removes the current q->rq_qos, this action has to be
done after queue is frozen, otherwise the IO queue path may never
be waken up, then IO hang is caused.

So fixes this issue by moving rq_qos_exit() after queue is frozen.

Cc: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: NMing Lei <ming.lei@redhat.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Dispatching a report zones command through the request queue is a major
pain due to the command reply payload rewriting necessary. Given that
blkdev_report_zones() is executing everything synchronously, implement
report zones as a block device file operation instead, allowing major
simplification of the code in many places.

sd, null-blk, dm-linear and dm-flakey being the only block device
drivers supporting exposing zoned block devices, these drivers are
modified to provide the device side implementation of the
report_zones() block device file operation.

For device mappers, a new report_zones() target type operation is
defined so that the upper block layer calls blkdev_report_zones() can
be propagated down to the underlying devices of the dm targets.
Implementation for this new operation is added to the dm-linear and
dm-flakey targets.
Reviewed-by: NHannes Reinecke <hare@suse.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
[Damien]
* Changed method block_device argument to gendisk
* Various bug fixes and improvements
* Added support for null_blk, dm-linear and dm-flakey.
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NMike Snitzer <snitzer@redhat.com>
Signed-off-by: NDamien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When submitting a bio, multiple recursive calls to make_request() may
occur. This causes the initial associate done in blkcg_bio_issue_check()
to be incorrect and reference the prior request_queue. This introduces
a helper to do reassociation when make_request() is recursively called.

Fixes: a7b39b4e ("blkcg: always associate a bio with a blkg")
Reported-by: NValdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: NDennis Zhou <dennis@kernel.org>
Tested-by: NValdis Kletnieks <valdis.kletnieks@vt.edu>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We just allocated the queue and haven't even set it up yet,
hence we know that checking if ->mq_ops is NULL is always
going to be true.

In fact we do need to assign a lock to ->queue_lock always,
as we need it for the queue flags modifications.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

blk_mq_realloc_hw_ctxs could be invoked during update hw queues.
At the momemt, IO is blocked. Change the gfp flags from GFP_KERNEL
to GFP_NOIO to avoid forever hang during memory allocation in
blk_mq_realloc_hw_ctxs.
Signed-off-by: NJianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>