linux-kernel - Re: [PATCH] fs: fix undefined behavior in bit shift for SB

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Date:   Mon, 31 Oct 2022 06:15:32 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Gaosheng Cui <cuigaosheng1@...wei.com>
Cc:     viro@...iv.linux.org.uk, dhowells@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: fix undefined behavior in bit shift for SB_NOUSER

On Sat, Oct 29, 2022 at 03:17:45PM +0800, Gaosheng Cui wrote:
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1396,7 +1396,7 @@ extern int send_sigurg(struct fown_struct *fown);
>  #define SB_NOSEC	(1<<28)
>  #define SB_BORN		(1<<29)
>  #define SB_ACTIVE	(1<<30)
> -#define SB_NOUSER	(1<<31)
> +#define SB_NOUSER	(1U<<31)

Let's mark all of the flags as unsigned instead of just one so that
we don't mix types.  s_flags is already unsigned (although for some
reason long) already.

And while you touch this please add the proper whitespaces around the
shift operator everywhere.