linux-kernel - Re: [PATCH] mm/z3fold.c: fix lock/unlock imbalance in z3fold_page

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Date:   Mon, 26 Aug 2019 16:05:15 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Cc:     Henry Burns <henryburns@...gle.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/z3fold.c: fix lock/unlock imbalance in
 z3fold_page_isolate

On Sun, 25 Aug 2019 22:06:34 -0500 "Gustavo A. R. Silva" <gustavo@...eddedor.com> wrote:

> Fix lock/unlock imbalance by unlocking *zhdr* before return.
> 
> Addresses-Coverity-ID: 1452811 ("Missing unlock")
> Fixes: d776aaa9895e ("mm/z3fold.c: fix race between migration and destruction")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  mm/z3fold.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index e31cd9bd4ed5..75b7962439ff 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -1406,6 +1406,7 @@ static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
>  				 * should freak out.
>  				 */
>  				WARN(1, "Z3fold is experiencing kref problems\n");
> +				z3fold_page_unlock(zhdr);
>  				return false;
>  			}
>  			z3fold_page_unlock(zhdr);

Looks good, thanks.


This is a bit silly:

			if (..) {
				...
				z3fold_page_unlock(zhdr);
				return false;
			}
			z3fold_page_unlock(zhdr);
			return false;

but presumably the compiler will clean up after us.