On Fri, Nov 30 2018 at 4:52pm -0500, Jens Axboe <[email protected]> wrote:
> On 11/30/18 2:44 PM, Mike Snitzer wrote: > > On Tue, Nov 27 2018 at 7:42pm -0500, > > Mikulas Patocka <[email protected]> wrote: > > > >> Now when part_round_stats is gone, we can switch to per-cpu in-flight > >> counters. > >> > >> We use the local-atomic type local_t, so that if part_inc_in_flight or > >> part_dec_in_flight is reentrantly called from an interrupt, the value will > >> be correct. > >> > >> The other counters could be corrupted due to reentrant interrupt, but the > >> corruption only results in slight counter skew - the in_flight counter > >> must be exact, so it needs local_t. > >> > >> Signed-off-by: Mikulas Patocka <[email protected]> > >> > >> --- > >> block/bio.c | 4 ++-- > >> block/blk-core.c | 4 ++-- > >> block/blk-merge.c | 2 +- > >> block/genhd.c | 47 > >> +++++++++++++++++++++++++++++++++++------------ > >> drivers/md/dm.c | 4 +--- > >> include/linux/genhd.h | 7 ++++--- > >> 6 files changed, 45 insertions(+), 23 deletions(-) > >> > >> Index: linux-block/block/genhd.c > >> =================================================================== > >> --- linux-block.orig/block/genhd.c 2018-11-28 00:09:59.000000000 +0100 > >> +++ linux-block/block/genhd.c 2018-11-28 00:09:59.000000000 +0100 > >> @@ -45,53 +45,76 @@ static void disk_add_events(struct gendi > >> static void disk_del_events(struct gendisk *disk); > >> static void disk_release_events(struct gendisk *disk); > >> > >> -void part_inc_in_flight(struct request_queue *q, struct hd_struct *part, > >> int rw) > >> +void part_inc_in_flight(struct request_queue *q, int cpu, struct > >> hd_struct *part, int rw) > >> { > >> if (queue_is_mq(q)) > >> return; > >> > >> - atomic_inc(&part->in_flight[rw]); > >> + local_inc(per_cpu_ptr(part->dkstats, cpu)->in_flight); > >> if (part->partno) > >> - atomic_inc(&part_to_disk(part)->part0.in_flight[rw]); > >> + local_inc(per_cpu_ptr(part_to_disk(part)->part0.dkstats, > >> cpu)->in_flight); > >> } > >> > >> -void part_dec_in_flight(struct request_queue *q, struct hd_struct *part, > >> int rw) > >> +void part_dec_in_flight(struct request_queue *q, int cpu, struct > >> hd_struct *part, int rw) > >> { > >> if (queue_is_mq(q)) > >> return; > >> > >> - atomic_dec(&part->in_flight[rw]); > >> + local_dec(per_cpu_ptr(part->dkstats, cpu)->in_flight); > >> if (part->partno) > >> - atomic_dec(&part_to_disk(part)->part0.in_flight[rw]); > >> + local_dec(per_cpu_ptr(part_to_disk(part)->part0.dkstats, > >> cpu)->in_flight); > >> } > > > > > > The above is wrong, needs this incremental fix: > > Should also be using this_cpu_inc/dec instead. How so? Mikulas is using local_t (original header speaks to why) -- dm-devel mailing list [email protected] https://www.redhat.com/mailman/listinfo/dm-devel
