submit_bio_wait() can be called from ioctl(BLKSECDISCARD), which may take long time to complete, as Salman mentioned, 4K BLKSECDISCARD takes up to 100 second on some devices. Also any block I/O operation that occurs after the BLKSECDISCARD is submitted will also potentially be affected by the hung task timeouts. Another report is that task hang can be observed when running mkfs over raid10 which takes a small max discard sectors limit because of chunk size. So prevent hung_check from firing by taking same approach used in blk_execute_rq(), and the wake-up interval is set as half the hung_check timer period, which keeps overhead low enough. Cc: Salman Qazi <sqazi@xxxxxxxxxx> Cc: Jesse Barnes <jsbarnes@xxxxxxxxxx> Cc: Bart Van Assche <bvanassche@xxxxxxx> Link: https://lkml.org/lkml/2020/2/12/1193 Reported-by: Salman Qazi <sqazi@xxxxxxxxxx> Reviewed-by: Jesse Barnes <jsbarnes@xxxxxxxxxx> Reviewed-by: Salman Qazi <sqazi@xxxxxxxxxx> Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- V2: - fix checkpatch warning - add reviewed-by - add comment log for covering one recent report on task hung on raid10 block/bio.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/block/bio.c b/block/bio.c index 94d697217887..0985f3422556 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 +1020,21 @@ 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); } -- 2.20.1
