Re: [PATCH] zsmalloc: Fix races between modifications of fullness and isolated

[Sergey Senozhatsky]

On (23/07/21 14:37), Andrew Yang wrote:
> 
> Since fullness and isolated share the same unsigned int,
> modifications of them should be protected by the same lock.
> 
> Signed-off-by: Andrew Yang <andrew.yang@xxxxxxxxxxxx>
> Fixes: c4549b871102 ("zsmalloc: remove zspage isolation for migration")

Have you observed issues in real life? That commit is more than a year
and a half old, so I wonder.

> @@ -1858,8 +1860,8 @@ static int zs_page_migrate(struct page *newpage, struct page *page,
>  	 * Since we complete the data copy and set up new zspage structure,
>  	 * it's okay to release the pool's lock.
>  	 */

This comment should be moved too, because this is not where we unlock the
pool anymore.

> -	spin_unlock(&pool->lock);
>  	dec_zspage_isolation(zspage);
> +	spin_unlock(&pool->lock);
>  	migrate_write_unlock(zspage);