Re: BLKSECDISCARD ioctl and hung tasks
From: Bart Van Assche <bvanassche@acm.org>
Date: 2020-02-13 17:48:29
Also in:
lkml
On 2/13/20 12:26 AM, Ming Lei wrote:
quoted hunk ↗ jump to hunk
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.