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Subject: Re: [PATCH 2/2] swap: Deal with PTE mapped THP when unuse PTE
From:   William Kucharski <william.kucharski@oracle.com>
In-Reply-To: <20181211084609.19553-2-ying.huang@intel.com>
Date:   Tue, 11 Dec 2018 07:32:07 -0700
Cc:     Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Vineeth Remanan Pillai <vpillai@digitalocean.com>,
        Kelley Nielsen <kelleynnn@gmail.com>,
        Rik van Riel <riel@surriel.com>,
        Matthew Wilcox <willy@infradead.org>,
        Hugh Dickins <hughd@google.com>
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Message-Id: <77D903B4-E63F-4633-8D5B-C39EFC067FB8@oracle.com>
References: <20181211084609.19553-1-ying.huang@intel.com>
 <20181211084609.19553-2-ying.huang@intel.com>
To:     Huang Ying <ying.huang@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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> ---
> mm/swapfile.c | 4 +---
> 1 file changed, 1 insertion(+), 3 deletions(-)
>=20
> 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;
> 		}
>=20
> -		if (PageSwapCache(page) && (swap_count(*swap_map) =3D=3D =
0))
> -			delete_from_swap_cache(compound_head(page));
> +		try_to_free_swap(page);
>=20
> -		SetPageDirty(page);
> 		unlock_page(page);
> 		put_page(page);
>=20
> --=20
> 2.18.1
>=20

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@oracle.com>=