linux-toradex.git/block/elevator.c, branch v4.17

block: Document scheduler modification locking requirements

2018-01-18T19:54:42+00:00

This patch does not change any functionality.

Reviewed-by: Christoph Hellwig 
Signed-off-by: Bart Van Assche 
Signed-off-by: Jens Axboe

block: Unexport elv_register_queue() and elv_unregister_queue()

2018-01-18T19:54:41+00:00

These two functions are only called from inside the block layer so
unexport them.

Reviewed-by: Christoph Hellwig 
Signed-off-by: Bart Van Assche 
Signed-off-by: Jens Axboe

blk-mq: quiesce queue during switching io sched and updating nr_requests

2018-01-06T16:25:36+00:00

Dispatch may still be in-progress after queue is frozen, so we have to
quiesce queue before switching IO scheduler and updating nr_requests.

Also when switching io schedulers, blk_mq_run_hw_queue() may still be
called somewhere(such as from nvme_reset_work()), and io scheduler's
per-hctx data may not be setup yet, so cause oops even inside
blk_mq_hctx_has_pending(), such as it can be run just between:

        ret = e->ops.mq.init_sched(q, e);
AND
        ret = e->ops.mq.init_hctx(hctx, i)

inside blk_mq_init_sched().

This reverts commit 7a148c2fcff8330(block: don't call blk_mq_quiesce_queue()
after queue is frozen) basically, and makes sure blk_mq_hctx_has_pending
won't be called if queue is quiesced.

Reviewed-by: Christoph Hellwig 
Fixes: 7a148c2fcff83309(block: don't call blk_mq_quiesce_queue() after queue is frozen)
Reported-by: Yi Zhang 
Tested-by: Yi Zhang 
Signed-off-by: Ming Lei 
Signed-off-by: Jens Axboe

elevator: allow name aliases

2017-10-25T18:36:50+00:00

Since we now lookup elevator types with the appropriate multiqueue
capability, allow schedulers to register with an alias alongside
the real name. This is in preparation for allowing 'mq-deadline'
to register an alias of 'deadline' as well.

Reviewed-by: Omar Sandoval 
Signed-off-by: Jens Axboe

elevator: lookup mq vs non-mq elevators

2017-10-25T18:36:45+00:00

If an IO scheduler is selected via elevator= and it doesn't match
the driver in question wrt blk-mq support, then we fail to boot.

The elevator= parameter is deprecated and only supported for
non-mq devices. Augment the elevator lookup API so that we
pass in if we're looking for an mq capable scheduler or not,
so that we only ever return a valid type for the queue in
question.

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=196695
Reviewed-by: Omar Sandoval 
Signed-off-by: Jens Axboe

block: remove QUEUE_FLAG_STACKABLE

2017-10-05T21:22:59+00:00

We already have a queue_is_rq_based helper to check if a request_queue
is request based, so we can remove the flag for it.

Acked-by: Mike Snitzer 
Signed-off-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

block: fix warning when I/O elevator is changed as request_queue is being removed

2017-08-28T16:52:44+00:00

There is a race between changing I/O elevator and request_queue removal
which can trigger the warning in kobject_add_internal.  A program can
use sysfs to request a change of elevator at the same time another task
is unregistering the request_queue the elevator would be attached to.
The elevator's kobject will then attempt to be connected to the
request_queue in the object tree when the request_queue has just been
removed from sysfs.  This triggers the warning in kobject_add_internal
as the request_queue no longer has a sysfs directory:

kobject_add_internal failed for iosched (error: -2 parent: queue)
------------[ cut here ]------------
WARNING: CPU: 3 PID: 14075 at lib/kobject.c:244 kobject_add_internal+0x103/0x2d0

To fix this warning, we can check the QUEUE_FLAG_REGISTERED flag when
changing the elevator and use the request_queue's sysfs_lock to
serialize between clearing the flag and the elevator testing the flag.

Signed-off-by: David Jeffery 
Tested-by: Ming Lei 
Reviewed-by: Ming Lei 
Signed-off-by: Jens Axboe

block: Add fallthrough markers to switch statements

2017-06-21T17:46:07+00:00

This patch suppresses gcc 7 warnings about falling through in switch
statements when building with W=1. From the gcc documentation: The
-Wimplicit-fallthrough=3 warning is enabled by -Wextra. See also
https://gcc.gnu.org/onlinedocs/gcc-7.1.0/gcc/Warning-Options.html.

Signed-off-by: Bart Van Assche 
Signed-off-by: Jens Axboe

elevator: remove redundant warnings on IO scheduler switch

2017-05-10T13:40:04+00:00

We warn twice for switching to a scheduler, if that switch fails.
As we also report the failure in the return value to the
sysfs write, remove the dmesg induced failures.

Keep the failure print for warning to switch to the kconfig
selected IO scheduler, as we can't report errors for that in
any other way.

Signed-off-by: Jens Axboe

block: don't call blk_mq_quiesce_queue() after queue is frozen

2017-05-02T17:33:08+00:00

After queue is frozen, no request in this queue can be in use at all, so
there can't be any .queue_rq() running on this queue.  It isn't
necessary to call blk_mq_quiesce_queue() any more, so remove it in both
elevator_switch_mq() and blk_mq_update_nr_requests().

Cc: Bart Van Assche 
Signed-off-by: Ming Lei 

Fixed up the description a bit.

Signed-off-by: Jens Axboe