Re: [RFC PATCH v2 1/7] mm: zswap: add pool shrinking mechanism

Johannes Weiner
2023-06-08T16:00:12Z

Hi Domenico,

Thanks for incorporating the feedback. Just two more nits:

On Tue, Jun 06, 2023 at 04:56:05PM +0200, Domenico Cerasuolo wrote:
> Each zpool driver (zbud, z3fold and zsmalloc) implements its own shrink
> function, which is called from zpool_shrink. However, with this commit,
> a unified shrink function is added to zswap. The ultimate goal is to
> eliminate the need for zpool_shrink once all zpool implementations have
> dropped their shrink code.
>
> To ensure the functionality of each commit, this change focuses solely
> on adding the mechanism itself. No modifications are made to
> the backends, meaning that functionally, there are no immediate changes.
> The zswap mechanism will only come into effect once the backends have
> removed their shrink code. The subsequent commits will address the
> modifications needed in the backends.
>
> Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> @@ -364,6 +375,12 @@ static void zswap_free_entry(struct zswap_entry *entry)
> if (!entry->length)
> atomic_dec(&zswap_same_filled_pages);
> else {
> + /* zpool_evictable will be removed once all 3 backends have migrated */
> + if (!zpool_evictable(entry->pool->zpool)) {

Comment indentation is off.

> + spin_lock(&entry->pool->lru_lock);
> + list_del(&entry->lru);
> + spin_unlock(&entry->pool->lru_lock);
> + }
> zpool_free(entry->pool->zpool, entry->handle);
> zswap_pool_put(entry->pool);
> }
> @@ -584,14 +601,70 @@ static struct zswap_pool *zswap_pool_find_get(char *type, char *compressor)
> return NULL;
> }
>
> +static int zswap_shrink(struct zswap_pool *pool)
> +{
> + struct zswap_entry *lru_entry, *tree_entry = NULL;
> + struct zswap_header *zhdr;
> + struct zswap_tree *tree;
> + int swpoffset;

pgoff_t

With that and what Yosry pointed out fixed, please feel free to add

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

to the next version.