linux-kernel - Re: [PATCH v2 6/8] fs: remove no

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Message-ID: <YreDvG7go6e5m1ox@zx2c4.com>
Date:   Sat, 25 Jun 2022 23:53:00 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
        Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2 6/8] fs: remove no_llseek

Hi Christoph,

On Sat, Jun 25, 2022 at 06:10:02AM -0700, Christoph Hellwig wrote:
> On Sat, Jun 25, 2022 at 01:01:13PM +0200, Jason A. Donenfeld wrote:
> > Now that all callers of ->llseek are going through vfs_llseek(), we
> > don't gain anything by keeping no_llseek around. Nothing compares it or
> > calls it.
> 
> Shouldn't this and the checks for no_llseek simply be merged into patch
> 2?

I'd done that at first, but Al had suggested it be a separate commit in
<https://lore.kernel.org/lkml/YrYxOC5dgCKBHwVE@ZenIV/>, when he mentions
"next commit would", so I did how he asked.

> 
> > +	if ((file->f_mode & FMODE_LSEEK) && file->f_op->llseek)
> > +		return file->f_op->llseek(file, offset, whence);
> > +	return -ESPIPE;
> 
> No function change, but in general checking for the error condition
> in the branch tends to be more readable.  i.e.:
> 
> 	if (!(file->f_mode & FMODE_LSEEK) || !file->f_op->llseek)
> 		return -ESPIPE;
> 	return file->f_op->llseek(file, offset, whence);
> 

I thought about this kind of reverse: what is the acceptable condition
in which one may call ->llseek? Easier to express it that way than in
the inverse. But if you really want, I can change it around if there's a
v3 with other changes (which at the moment doesn't seem like there's
going to be).

Jason