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    Subject[PATCH 4.19 23/30] dm stats: add cond_resched when looping over entries
    Date
    From: Mikulas Patocka <mpatocka@redhat.com>

    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@vger.kernel.org
    Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
    Signed-off-by: Mike Snitzer <snitzer@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    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)

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