Re: [PATCH 6/7] libxfs: keep unflushable buffers off the cache MRUs

Christoph Hellwig
2016-02-08T10:06:45Z

> --- a/include/cache.h
> +++ b/include/cache.h
> @@ -51,6 +51,7 @@ enum {
> #define CACHE_BASE_PRIORITY 0
> #define CACHE_PREFETCH_PRIORITY 8
> #define CACHE_MAX_PRIORITY 15
> +#define CACHE_DIRTY_PRIORITY (CACHE_MAX_PRIORITY + 1)

Sizing arrays based on, and iterating up to CACHE_DIRTY_PRIORITY seems
rather odd. Maybe add a new

#define CACHE_NR_PRIORITIES CACHE_DIRTY_PRIORITY

and a comment explaining the magic to make it more obvious?

> +cache_move_to_dirty_mru(
> + struct cache *cache,
> + struct cache_node *node)
> +{
> + struct cache_mru *mru;
> +
> + mru = &cache->c_mrus[CACHE_DIRTY_PRIORITY];
> +
> + pthread_mutex_lock(&mru->cm_mutex);
> + node->cn_priority = CACHE_DIRTY_PRIORITY;
> + list_move(&node->cn_mru, &mru->cm_list);
> + mru->cm_count++;
> + pthread_mutex_unlock(&mru->cm_mutex);
> +}

Maybe it would better to just do a list_add here and leave the
list_del to the caller to avoid needing to nest two different
cm_mutex instances.