On Mon, 11 Sep 2017, Mike Snitzer wrote: > On Mon, Jul 24 2017 at 5:16am -0400, > Damien Le Moal <damien.lemoal@xxxxxxx> wrote: > > > > > > > On 7/24/17 17:03, Christoph Hellwig wrote: > > > On Mon, Jul 24, 2017 at 04:44:22PM +0900, Damien Le Moal wrote: > > >> Avoid metadata flush to be blocked by the writeback throttling code in > > >> wbt_wait(). Otherwise, we can end up with a deadlock under heavy write > > >> load with all chunk works active. In such situation, a deadlock can > > >> happen if the flush work is blocked by the throttling code while holding > > >> the metadata lock: as the chunk works will wait for the metadata lock > > >> too, no progress can be made. Could you explain, what's the specific problem here? The writeback throttling code is executed at request level and the dm-zoned target working above it, at bio level. So I don't see how dm-zoned progress could be blocked by writeback throttling. Maybe you have some other bug in your code and this patch just masks it? Mikulas > > >> Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx> > > >> --- > > >> drivers/md/dm-zoned-metadata.c | 3 ++- > > >> 1 file changed, 2 insertions(+), 1 deletion(-) > > >> > > >> diff --git a/drivers/md/dm-zoned-metadata.c b/drivers/md/dm-zoned-metadata.c > > >> index 884ff7c170a0..f694fb98b002 100644 > > >> --- a/drivers/md/dm-zoned-metadata.c > > >> +++ b/drivers/md/dm-zoned-metadata.c > > >> @@ -567,7 +567,8 @@ static void dmz_write_mblock(struct dmz_metadata *zmd, struct dmz_mblock *mblk, > > >> bio->bi_bdev = zmd->dev->bdev; > > >> bio->bi_private = mblk; > > >> bio->bi_end_io = dmz_mblock_bio_end_io; > > >> - bio_set_op_attrs(bio, REQ_OP_WRITE, REQ_META | REQ_PRIO); > > >> + bio_set_op_attrs(bio, REQ_OP_WRITE, > > >> + REQ_META | REQ_PRIO | REQ_SYNC | REQ_IDLE); > > > > > > Please just assign bi_opf directly instea dof using bio_set_op_attrs > > > in new code. > > > > OK. Will do. > > > > > Also what do you need REQ_IDLE for? > > > > It is not really needed here, but the wbt_should_throttle() code test is: > > > > if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) == (REQ_SYNC | REQ_IDLE)) > > return false; > > > > So if REQ_IDLE is not set, wbt will trigger. > > > > Having a req flag that says "no wb throttling please" would be a lot > > cleaner... > > Did you have a new version of this patch? > > Thanks, > Mike > -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
