Commit 0cdb90f0 authored by Mike Snitzer's avatar Mike Snitzer
Browse files

dm stats: fix too short end duration_ns when using precise_timestamps 



dm_stats_account_io()'s STAT_PRECISE_TIMESTAMPS support doesn't handle
the fact that with commit b879f915 ("dm: properly fix redundant
bio-based IO accounting") io->start_time _may_ be in the past (meaning
the start_io_acct() was deferred until later).

Add a new dm_stats_recalc_precise_timestamps() helper that will
set/clear a new 'precise_timestamps' flag in the dm_stats struct based
on whether any configured stats enable STAT_PRECISE_TIMESTAMPS.
And update DM core's alloc_io() to use dm_stats_record_start() to set
stats_aux.duration_ns if stats->precise_timestamps is true.

Also, remove unused 'last_sector' and 'last_rw' members from the
dm_stats struct.

Fixes: b879f915 ("dm: properly fix redundant bio-based IO accounting")
Cc: stable@vger.kernel.org
Co-developed-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent 8d394bc4

drivers/md/dm-stats.c

+25 −3
Original line number Diff line number Diff line
@@ -195,6 +195,7 @@ void dm_stats_init(struct dm_stats *stats) 


	mutex_init(&stats->mutex);

	INIT_LIST_HEAD(&stats->list);

	stats->precise_timestamps = false;

	stats->last = alloc_percpu(struct dm_stats_last_position);

	for_each_possible_cpu(cpu) {

		last = per_cpu_ptr(stats->last, cpu);
@@ -231,6 +232,22 @@ void dm_stats_cleanup(struct dm_stats *stats) 
	mutex_destroy(&stats->mutex);

}



static void dm_stats_recalc_precise_timestamps(struct dm_stats *stats)

{

	struct list_head *l;

	struct dm_stat *tmp_s;

	bool precise_timestamps = false;



	list_for_each(l, &stats->list) {

		tmp_s = container_of(l, struct dm_stat, list_entry);

		if (tmp_s->stat_flags & STAT_PRECISE_TIMESTAMPS) {

			precise_timestamps = true;

			break;

		}

	}

	stats->precise_timestamps = precise_timestamps;

}



static int dm_stats_create(struct dm_stats *stats, sector_t start, sector_t end,

			   sector_t step, unsigned stat_flags,

			   unsigned n_histogram_entries,
@@ -376,6 +393,9 @@ static int dm_stats_create(struct dm_stats *stats, sector_t start, sector_t end, 
	}

	ret_id = s->id;

	list_add_tail_rcu(&s->list_entry, l);



	dm_stats_recalc_precise_timestamps(stats);



	mutex_unlock(&stats->mutex);



	resume_callback(md);
@@ -418,6 +438,9 @@ static int dm_stats_delete(struct dm_stats *stats, int id) 
	}



	list_del_rcu(&s->list_entry);



	dm_stats_recalc_precise_timestamps(stats);



	mutex_unlock(&stats->mutex);



	/*
@@ -656,9 +679,8 @@ void dm_stats_account_io(struct dm_stats *stats, unsigned long bi_rw, 
	got_precise_time = false;

	list_for_each_entry_rcu(s, &stats->list, list_entry) {

		if (s->stat_flags & STAT_PRECISE_TIMESTAMPS && !got_precise_time) {

			if (!end)

				stats_aux->duration_ns = ktime_to_ns(ktime_get());

			else

			/* start (!end) duration_ns is set by DM core's alloc_io() */

			if (end)

				stats_aux->duration_ns = ktime_to_ns(ktime_get()) - stats_aux->duration_ns;

			got_precise_time = true;

		}

drivers/md/dm-stats.h

+7 −2
Original line number Diff line number Diff line
@@ -13,8 +13,7 @@ struct dm_stats { 
	struct mutex mutex;

	struct list_head list;	/* list of struct dm_stat */

	struct dm_stats_last_position __percpu *last;

	sector_t last_sector;

	unsigned last_rw;

	bool precise_timestamps;

};



struct dm_stats_aux {
@@ -40,4 +39,10 @@ static inline bool dm_stats_used(struct dm_stats *st) 
	return !list_empty(&st->list);

}



static inline void dm_stats_record_start(struct dm_stats *stats, struct dm_stats_aux *aux)

{

	if (unlikely(stats->precise_timestamps))

		aux->duration_ns = ktime_to_ns(ktime_get());

}



#endif

drivers/md/dm.c

+2 −0
Original line number Diff line number Diff line
@@ -552,6 +552,8 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio) 


	io->start_time = jiffies;



	dm_stats_record_start(&md->stats, &io->stats_aux);



	return io;

}