linux-kernel - Re: [PATCH v4 1/9] mm/swap: fix uninitialized compiler warning

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Message-ID: <20191119154138.GB382712@cmpxchg.org>
Date:   Tue, 19 Nov 2019 10:41:38 -0500
From:   Johannes Weiner <hannes@...xchg.org>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org,
        mgorman@...hsingularity.net, tj@...nel.org, hughd@...gle.com,
        khlebnikov@...dex-team.ru, daniel.m.jordan@...cle.com,
        yang.shi@...ux.alibaba.com, willy@...radead.org,
        shakeelb@...gle.com
Subject: Re: [PATCH v4 1/9] mm/swap: fix uninitialized compiler warning

On Tue, Nov 19, 2019 at 08:23:15PM +0800, Alex Shi wrote:
>   ../mm/swap.c: In function ‘__page_cache_release’:
>   ../mm/swap.c:67:10: warning: ‘flags’ may be used uninitialized in this
>   function [-Wmaybe-uninitialized]
>        lruvec = lock_page_lruvec_irqsave(page, pgdat, flags);
>        ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

At this point in the series, there is no lock_page_lruvec_irqsave()
yet, so this patch is out of order. Please don't do that. It's very
hard to review patches that depend on later changes to make sense.

> Signed-off-by: Alex Shi <alex.shi@...ux.alibaba.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  mm/swap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/swap.c b/mm/swap.c
> index 5341ae93861f..c36a10244d07 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -62,7 +62,7 @@ static void __page_cache_release(struct page *page)
>  	if (PageLRU(page)) {
>  		pg_data_t *pgdat = page_pgdat(page);
>  		struct lruvec *lruvec;
> -		unsigned long flags;
> +		unsigned long flags = 0;

Use unintialized_var() for these cases to make the intent clear.