[PATCH 4.19 23/30] dm stats: add cond_resched when looping over entries

[Greg Kroah-Hartman]

From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

commit bfe2b0146c4d0230b68f5c71a64380ff8d361f8b upstream.

dm-stats can be used with a very large number of entries (it is only
limited by 1/4 of total system memory), so add rescheduling points to
the loops that iterate over the entries.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/md/dm-stats.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/drivers/md/dm-stats.c
+++ b/drivers/md/dm-stats.c
@@ -224,6 +224,7 @@ void dm_stats_cleanup(struct dm_stats *s
 				       atomic_read(&shared->in_flight[READ]),
 				       atomic_read(&shared->in_flight[WRITE]));
 			}
+			cond_resched();
 		}
 		dm_stat_free(&s->rcu_head);
 	}
@@ -313,6 +314,7 @@ static int dm_stats_create(struct dm_sta
 	for (ni = 0; ni < n_entries; ni++) {
 		atomic_set(&s->stat_shared[ni].in_flight[READ], 0);
 		atomic_set(&s->stat_shared[ni].in_flight[WRITE], 0);
+		cond_resched();
 	}
 
 	if (s->n_histogram_entries) {
@@ -325,6 +327,7 @@ static int dm_stats_create(struct dm_sta
 		for (ni = 0; ni < n_entries; ni++) {
 			s->stat_shared[ni].tmp.histogram = hi;
 			hi += s->n_histogram_entries + 1;
+			cond_resched();
 		}
 	}
 
@@ -345,6 +348,7 @@ static int dm_stats_create(struct dm_sta
 			for (ni = 0; ni < n_entries; ni++) {
 				p[ni].histogram = hi;
 				hi += s->n_histogram_entries + 1;
+				cond_resched();
 			}
 		}
 	}
@@ -474,6 +478,7 @@ static int dm_stats_list(struct dm_stats
 			}
 			DMEMIT("\n");
 		}
+		cond_resched();
 	}
 	mutex_unlock(&stats->mutex);
 
@@ -750,6 +755,7 @@ static void __dm_stat_clear(struct dm_st
 				local_irq_enable();
 			}
 		}
+		cond_resched();
 	}
 }
 
@@ -865,6 +871,8 @@ static int dm_stats_print(struct dm_stat
 
 		if (unlikely(sz + 1 >= maxlen))
 			goto buffer_overflow;
+
+		cond_resched();
 	}
 
 	if (clear)