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.
