On Fri, Feb 22 2019 at 10:22am -0500, Mike Snitzer <[email protected]> wrote:
> On Fri, Feb 22 2019 at 5:59am -0500, > Mikulas Patocka <[email protected]> wrote: > > > Hi > > > > I've fonud out that this patch causes timeout in the lvm test > > shell/activate-missing-segment.sh and some others. > > OK, I can reproduce with: > make check_local T=shell/activate-missing-segment.sh > > Interestingly, it isn't hung in kernel, test can be interrupted. > And it is hanging at shell/activate-missing-segment.sh's : aux disable_dev > "$dev1" > > Other tests with "aux disable_dev" hang too > (e.g. shell/lvcreate-repair.sh, shell/vgreduce-usage.sh) > > continued below: > > > On Wed, 20 Feb 2019, Mike Snitzer wrote: > > > > > Leverage fact that dm_queue_split() enables use of noclone support even > > > for targets that require additional splitting (via ti->max_io_len). > > > > > > To achieve this move noclone processing from dm_make_request() to > > > dm_process_bio() and check if bio->bi_end_io is already set to > > > noclone_endio. This also fixes dm_wq_work() to be able to support > > > noclone bios (because it calls dm_process_bio()). > > > > > > While at it, clean up ->map() return processing to be comparable to > > > __map_bio() and add some code comments that explain why certain > > > conditionals exist to prevent the use of noclone. > > > > > > Signed-off-by: Mike Snitzer <[email protected]> > > > --- > > > drivers/md/dm.c | 103 > > > ++++++++++++++++++++++++++++++++++---------------------- > > > 1 file changed, 62 insertions(+), 41 deletions(-) > > > > > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > > > index 57919f211acc..d84735be6927 100644 > > > --- a/drivers/md/dm.c > > > +++ b/drivers/md/dm.c > > > @@ -1764,14 +1764,75 @@ static blk_qc_t dm_process_bio(struct > > > mapped_device *md, > > > * If in ->make_request_fn we need to use blk_queue_split(), otherwise > > > * queue_limits for abnormal requests (e.g. discard, writesame, etc) > > > * won't be imposed. > > > + * > > > + * For normal READ and WRITE requests we benefit from upfront splitting > > > + * via dm_queue_split() because we can then leverage noclone support > > > below. > > > */ > > > - if (current->bio_list) { > > > + if (current->bio_list && (bio->bi_end_io != noclone_endio)) { > > > + /* > > > + * It is fine to use {blk,dm}_queue_split() before opting to > > > use noclone > > > + * because any ->bi_private and ->bi_end_io will get saved off > > > below. > > > + * Once noclone_endio() is called the bio_chain's endio will > > > kick in. > > > + * - __split_and_process_bio() can split further, but any > > > targets that > > > + * require late _DM_ initiated splitting (e.g. > > > dm_accept_partial_bio() > > > + * callers) shouldn't set ti->no_clone. > > > + */ > > > if (is_abnormal_io(bio)) > > > blk_queue_split(md->queue, &bio); > > > else > > > dm_queue_split(md, ti, &bio); > > > } > > > > > > + if (dm_table_supports_noclone(map) && > > > + (bio_op(bio) == REQ_OP_READ || bio_op(bio) == REQ_OP_WRITE) && > > > + likely(!(bio->bi_opf & REQ_PREFLUSH)) && > > > + likely(!bio_integrity(bio)) && /* integrity requires specialized > > > processing */ > > > + likely(!dm_stats_used(&md->stats))) { /* noclone doesn't support > > > dm-stats */ > > > + int r; > > > + struct dm_noclone *noclone; > > > + > > > + /* Already been here if bio->bi_end_io is noclone_endio, > > > reentered via dm_wq_work() */ > > > + if (bio->bi_end_io != noclone_endio) { > > This conditional is causing it ^ > > Very strange... Added some debugging: Feb 22 10:46:28 thegoat kernel: device-mapper: core: dm_process_bio: 253:2: bio=00000000c70f3c09 bio->bi_iter.bi_sector=0 len=256 bio->bi_end_io != noclone_endio Feb 22 10:46:28 thegoat kernel: device-mapper: core: dm_process_bio: 253:0: bio=00000000c70f3c09 bio->bi_iter.bi_sector=2048 len=256 bio->bi_end_io = noclone_endio ... Feb 22 10:46:28 thegoat kernel: device-mapper: core: dm_process_bio: 253:2: bio=00000000da9cadf3 bio->bi_iter.bi_sector=0 len=256 bio->bi_end_io != noclone_endio Feb 22 10:46:28 thegoat kernel: device-mapper: core: dm_process_bio: 253:0: bio=00000000da9cadf3 bio->bi_iter.bi_sector=2048 len=256 bio->bi_end_io = noclone_endio So the same noclone bio is entering devices in the stacked DM device (perfectly normal). This fixes the issue: diff --git a/drivers/md/dm.c b/drivers/md/dm.c index a9856f1986df..8fbe4d5ec8e4 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -1831,15 +1831,16 @@ static blk_qc_t dm_process_bio(struct mapped_device *md, likely(!bio_integrity(bio)) && /* integrity requires specialized processing */ likely(!dm_stats_used(&md->stats))) { /* noclone doesn't support dm-stats */ int r; - struct dm_noclone *noclone; - - /* Already been here if bio->bi_end_io is noclone_endio, reentered via dm_wq_work() */ - if (bio->bi_end_io != noclone_endio) { + /* + * Only allocate noclone if in ->make_request_fn, otherwise + * leak could occur due to reentering (e.g. from dm_wq_work) + */ + if (current->bio_list) { + struct dm_noclone *noclone; noclone = kmalloc_node(sizeof(*noclone) + ti->per_io_data_size + sizeof(unsigned), GFP_NOWAIT, md->numa_node_id); if (unlikely(!noclone)) goto no_fast_path; - noclone->md = md; noclone->start_time = jiffies; noclone->orig_bi_end_io = bio->bi_end_io; That said, I've reasoned through other edge cases that need to be dealt with and will layer other fixes in addition to this one. -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
