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Date: Thu, 13 Feb 2020 09:48:25 -0800 From: Bart Van Assche <bvanassche@....org> To: Ming Lei <ming.lei@...hat.com>, Salman Qazi <sqazi@...gle.com> Cc: Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, linux-block@...r.kernel.org, Gwendal Grignou <gwendal@...gle.com>, Jesse Barnes <jsbarnes@...gle.com> Subject: Re: BLKSECDISCARD ioctl and hung tasks On 2/13/20 12:26 AM, Ming Lei wrote: > The approach used in blk_execute_rq() can be borrowed for workaround the > issue, such as: > > diff --git a/block/bio.c b/block/bio.c > index 94d697217887..c9ce19a86de7 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -17,6 +17,7 @@ > #include <linux/cgroup.h> > #include <linux/blk-cgroup.h> > #include <linux/highmem.h> > +#include <linux/sched/sysctl.h> > > #include <trace/events/block.h> > #include "blk.h" > @@ -1019,12 +1020,19 @@ static void submit_bio_wait_endio(struct bio *bio) > int submit_bio_wait(struct bio *bio) > { > DECLARE_COMPLETION_ONSTACK_MAP(done, bio->bi_disk->lockdep_map); > + unsigned long hang_check; > > bio->bi_private = &done; > bio->bi_end_io = submit_bio_wait_endio; > bio->bi_opf |= REQ_SYNC; > submit_bio(bio); > - wait_for_completion_io(&done); > + > + /* Prevent hang_check timer from firing at us during very long I/O */ > + hang_check = sysctl_hung_task_timeout_secs; > + if (hang_check) > + while (!wait_for_completion_io_timeout(&done, hang_check * (HZ/2))); > + else > + wait_for_completion_io(&done); > > return blk_status_to_errno(bio->bi_status); > } Instead of suppressing the hung task complaints, has it been considered to use the bio splitting mechanism to make discard bios smaller? Block drivers may set a limit by calling blk_queue_max_discard_segments(). From block/blk-settings.c: /** * blk_queue_max_discard_segments - set max segments for discard * requests * @q: the request queue for the device * @max_segments: max number of segments * * Description: * Enables a low level driver to set an upper limit on the number of * segments in a discard request. **/ void blk_queue_max_discard_segments(struct request_queue *q, unsigned short max_segments) { q->limits.max_discard_segments = max_segments; } EXPORT_SYMBOL_GPL(blk_queue_max_discard_segments); Thanks, Bart.
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