[dm-devel] [PATCH] block: make discard killable

[Christoph Hellwig]

On Fri, Jul 06, 2018 at 07:51:30AM -0600, Jens Axboe wrote:
> On 7/3/18 11:35 AM, Mikulas Patocka wrote:
> > Discarding can take very long time for some device mapper targets, this
> > patch makes it possible to kill a process that issues the BLKDISCARD
> > ioctl.
> > 
> > Note that some filesystems call blkdev_issue_discard or
> > __blkdev_issue_discard directly, they may not be prepared to handle the
> > failure, so this patch introduces a flag BLKDEV_DISCARD_KILLABLE that is
> > only set when the discard is initiated by an ioctl.
> 
> This might be cleaner as a regular request flag, since killable can
> apply to other types of IO as well - like readahead.

He doesn't actually make the request killable, but just the
synchronous submission loop.  I have an actually killable version
of blk_execute_rq on m short-term todo plate as we want it for the
nvme passthrough ioctls.  That might be useful for discard as well.