linux-kernel - Re: [PATCH] proc: smoke test lseek()

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Message-ID: <YG4QymNCjgGR/cPk@localhost.localdomain>
Date:   Wed, 7 Apr 2021 23:06:34 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] proc: smoke test lseek()

On Wed, Apr 07, 2021 at 08:58:09PM +0100, Matthew Wilcox wrote:
> On Wed, Apr 07, 2021 at 10:55:14PM +0300, Alexey Dobriyan wrote:
> > Now that ->proc_lseek has been made mandatory it would be nice to test
> > that nothing has been forgotten.
> 
> > @@ -45,6 +45,8 @@ static void f_reg(DIR *d, const char *filename)
> >  	fd = openat(dirfd(d), filename, O_RDONLY|O_NONBLOCK);
> >  	if (fd == -1)
> >  		return;
> > +	/* struct proc_ops::proc_lseek is mandatory if file is seekable. */
> > +	(void)lseek(fd, 0, SEEK_SET);
> >  	rv = read(fd, buf, sizeof(buf));
> >  	assert((0 <= rv && rv <= sizeof(buf)) || rv == -1);
> >  	close(fd);
> 
> why throw away the return value?  if it returns an error seeking to
> offset 0, something is terribly wrong.

Some files may use nonseekable_open().
This smoke test doesn't verify that seeking is done correctly anyway.