On Wed, Nov 23, 2016 at 12:17:45PM -0800, Song Liu wrote:
> With writeback cache, we define log space critical as
>
> free_space < 2 * reclaim_required_space
>
> So the deassert of R5C_LOG_CRITICAL could happen when
> 1. free_space increases
> 2. reclaim_required_space decreases
>
> Currently, run_no_space_stripes() is called when 1 happens, but
> not (always) when 2 happens.
>
> With this patch, run_no_space_stripes() is call when
> R5C_LOG_CRITICAL is cleared.
>
> Signed-off-by: Song Liu <songliubraving@xxxxxx>
> ---
> drivers/md/raid5-cache.c | 13 ++++++++++++-
> 1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
> index 8cb79fc..0e24aab 100644
> --- a/drivers/md/raid5-cache.c
> +++ b/drivers/md/raid5-cache.c
> @@ -370,6 +370,7 @@ static inline void r5c_update_log_state(struct r5l_log *log)
> struct r5conf *conf = log->rdev->mddev->private;
> sector_t free_space;
> sector_t reclaim_space;
> + bool wake_reclaim = false;
>
> if (!r5c_is_writeback(log))
> return;
> @@ -379,12 +380,18 @@ static inline void r5c_update_log_state(struct r5l_log *log)
> reclaim_space = r5c_log_required_to_flush_cache(conf);
> if (free_space < 2 * reclaim_space)
> set_bit(R5C_LOG_CRITICAL, &conf->cache_state);
> - else
> + else {
> + if (test_bit(R5C_LOG_CRITICAL, &conf->cache_state))
> + wake_reclaim = true;
> clear_bit(R5C_LOG_CRITICAL, &conf->cache_state);
> + }
This doesn't look correct. shouldn't we clear the bit and do the wakeup right
after stripe_in_journal_count is decreased? Actually all these clear_bit looks
wrong. They should be cleared right after the condition met. In current
implementation, if no new stripe comes, r5c_update_log_state will not get
called.
> if (free_space < 3 * reclaim_space)
> set_bit(R5C_LOG_TIGHT, &conf->cache_state);
> else
> clear_bit(R5C_LOG_TIGHT, &conf->cache_state);
> +
> + if (wake_reclaim)
> + r5l_wake_reclaim(log, 0);
> }
>
> /*
> @@ -1348,6 +1355,10 @@ static void r5c_do_reclaim(struct r5conf *conf)
> spin_unlock(&conf->device_lock);
> spin_unlock_irqrestore(&log->stripe_in_journal_lock, flags);
> }
> +
> + if (!test_bit(R5C_LOG_CRITICAL, &conf->cache_state))
> + r5l_run_no_space_stripes(log);
> +
Why this? r5l_do_reclaim will call r5l_run_no_space_stripes.
Thanks,
Shaohua
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
