linux-kernel - Re: [PATCH 1/2] virtiofs, dax: Fix smatch warning about loss of info during shift

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Date:   Mon, 10 May 2021 14:16:23 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        linux-fsdevel@...r.kernel.org, virtio-fs@...hat.com,
        miklos@...redi.hu, linux-kernel@...r.kernel.org,
        dan.carpenter@...cle.com
Subject: Re: [PATCH 1/2] virtiofs, dax: Fix smatch warning about loss of info
 during shift

On Thu, May 06, 2021 at 12:35:17PM -0700, Matthew Wilcox wrote:
> On Thu, May 06, 2021 at 08:07:39PM +0100, Dr. David Alan Gilbert wrote:
> > > @@ -186,7 +186,7 @@ static int fuse_setup_one_mapping(struct inode *inode, unsigned long start_idx,
> > >  	struct fuse_conn_dax *fcd = fm->fc->dax;
> > >  	struct fuse_inode *fi = get_fuse_inode(inode);
> > >  	struct fuse_setupmapping_in inarg;
> > > -	loff_t offset = start_idx << FUSE_DAX_SHIFT;
> > > +	loff_t offset = (loff_t)start_idx << FUSE_DAX_SHIFT;
> > 
> > I've not followed the others back, but isn't it easier to change
> > the start_idx parameter to be a loff_t, since the places it's called
> > from are poth loff_t pos?
> 
> But an index isn't a file offset, and shouldn't be typed as such.

Agreed. This is index, so it seems better to not use "loff_t" to
represent it.

Vivek