linux-kernel - Re: [PATCH 2/2] swap: Deal with PTE mapped THP when unuse PTE

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Date:   Tue, 11 Dec 2018 07:32:07 -0700
From:   William Kucharski <william.kucharski@...cle.com>
To:     Huang Ying <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Vineeth Remanan Pillai <vpillai@...italocean.com>,
        Kelley Nielsen <kelleynnn@...il.com>,
        Rik van Riel <riel@...riel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH 2/2] swap: Deal with PTE mapped THP when unuse PTE



> ---
> mm/swapfile.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 7464d0a92869..9e6da494781f 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1921,10 +1921,8 @@ static int unuse_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
> 			goto out;
> 		}
> 
> -		if (PageSwapCache(page) && (swap_count(*swap_map) == 0))
> -			delete_from_swap_cache(compound_head(page));
> +		try_to_free_swap(page);
> 
> -		SetPageDirty(page);
> 		unlock_page(page);
> 		put_page(page);
> 
> -- 
> 2.18.1
> 

Since try_to_free_swap() can return 0 under certain error conditions, you should check
check for a return status of 1 before calling unlock_page() and put_page().

Reviewed-by: William Kucharski <william.kucharski@...cle.com>