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Subject: Re: [PATCH] z3fold: fix memory leak in kmem cache
To:     Vitaly Wool <vitalywool@gmail.com>, Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Cc:     Dan Streetman <ddstreet@ieee.org>, markus.linnala@gmail.com
References: <20190917185352.44cf285d3ebd9e64548de5de@gmail.com>
From:   Vlastimil Babka <vbabka@suse.cz>
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Message-ID: <d6214fbd-e757-43a9-ab12-4b61fde434db@suse.cz>
Date:   Wed, 18 Sep 2019 09:31:40 +0200
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On 9/17/19 5:53 PM, Vitaly Wool wrote:
> Currently there is a leak in init_z3fold_page() -- it allocates
> handles from kmem cache even for headless pages, but then they are
> never used and never freed, so eventually kmem cache may get
> exhausted. This patch provides a fix for that.
> 
> Reported-by: Markus Linnala <markus.linnala@gmail.com>
> Signed-off-by: Vitaly Wool <vitalywool@gmail.com>

Can a Fixes: commit be pinpointed, and CC stable added?

> ---
>  mm/z3fold.c | 15 +++++++++------
>  1 file changed, 9 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 6397725b5ec6..7dffef2599c3 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -301,14 +301,11 @@ static void z3fold_unregister_migration(struct z3fold_pool *pool)
>   }
>  
>  /* Initializes the z3fold header of a newly allocated z3fold page */
> -static struct z3fold_header *init_z3fold_page(struct page *page,
> +static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
>  					struct z3fold_pool *pool, gfp_t gfp)
>  {
>  	struct z3fold_header *zhdr = page_address(page);
> -	struct z3fold_buddy_slots *slots = alloc_slots(pool, gfp);
> -
> -	if (!slots)
> -		return NULL;
> +	struct z3fold_buddy_slots *slots;
>  
>  	INIT_LIST_HEAD(&page->lru);
>  	clear_bit(PAGE_HEADLESS, &page->private);
> @@ -316,6 +313,12 @@ static struct z3fold_header *init_z3fold_page(struct page *page,
>  	clear_bit(NEEDS_COMPACTING, &page->private);
>  	clear_bit(PAGE_STALE, &page->private);
>  	clear_bit(PAGE_CLAIMED, &page->private);
> +	if (headless)
> +		return zhdr;
> +
> +	slots = alloc_slots(pool, gfp);
> +	if (!slots)
> +		return NULL;
>  
>  	spin_lock_init(&zhdr->page_lock);
>  	kref_init(&zhdr->refcount);
> @@ -962,7 +965,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
>  	if (!page)
>  		return -ENOMEM;
>  
> -	zhdr = init_z3fold_page(page, pool, gfp);
> +	zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
>  	if (!zhdr) {
>  		__free_page(page);
>  		return -ENOMEM;
>