linux-kernel - Re: [PATCH v2] fs/btrfs: Fix uninitialized variable

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Date:   Tue, 20 Apr 2021 14:20:51 +0100
From:   Khaled Romdhani <khaledromdhani216@...il.com>
To:     David Sterba <dsterba@...e.cz>, clm@...com, josef@...icpanda.com
Cc:     linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org, khaledromdhani216@...il.com
Subject: Re: [PATCH v2] fs/btrfs: Fix uninitialized variable

On Mon, Apr 19, 2021 at 07:32:25PM +0200, David Sterba wrote:
> On Sat, Apr 17, 2021 at 04:36:16PM +0100, Khaled ROMDHANI wrote:
> > As reported by the Coverity static analysis.
> > The variable zone is not initialized which
> > may causes a failed assertion.
> > 
> > Addresses-Coverity: ("Uninitialized variables")
> > Signed-off-by: Khaled ROMDHANI <khaledromdhani216@...il.com>
> > ---
> > v2: add a default case as proposed by David Sterba
> > ---
> >  fs/btrfs/zoned.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
> > index eeb3ebe11d7a..82527308d165 100644
> > --- a/fs/btrfs/zoned.c
> > +++ b/fs/btrfs/zoned.c
> > @@ -143,6 +143,9 @@ static inline u32 sb_zone_number(int shift, int mirror)
> >  	case 0: zone = 0; break;
> >  	case 1: zone = 1ULL << (BTRFS_SB_LOG_FIRST_SHIFT - shift); break;
> >  	case 2: zone = 1ULL << (BTRFS_SB_LOG_SECOND_SHIFT - shift); break;
> > +	default:
> > +		zone = 0;
> 
> Well yeah but this is not a valid case at all, we'd rather catch that as
> an assertion failure than letting is silently continue.

So, as all callers pass valid value. It would be
better to catch that as an assertion failure.