linux-kernel - Re: [PATCH] ramfs: ignore tmpfs options when we emulate it

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Date:	Sun, 14 Jun 2009 19:49:35 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Mike Frysinger <vapier.adi@...il.com>
Cc:	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Matt Mackall <mpm@...enic.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ramfs: ignore tmpfs options when we emulate it

On Sun, Jun 14, 2009 at 07:26:37PM +0800, Mike Frysinger wrote:
> On Sun, Jun 14, 2009 at 07:14, Wu Fengguang wrote:
> > On Sun, Jun 14, 2009 at 06:46:24PM +0800, Mike Frysinger wrote:
> >> On Sun, Jun 14, 2009 at 06:42, Wu Fengguang wrote:
> >> > On Sun, Jun 14, 2009 at 06:01:10PM +0800, Wu Fengguang wrote:
> >> > Sorry I take back the previous patch. It makes sense to not break
> >> > existing user space tools, but a warning message looks OK to remind
> >> > people of possibly unexpected behavior.
> >> >
> >> >                default:
> >> >                        printk(KERN_ERR "ramfs: bad mount option: %s\n", p);
> >> > -                       return -EINVAL;
> >> > +                       break;
> >>
> >> hmm, if the warning was wrapped in #ifdef CONFIG_SHMEM, i'd be ok with
> >> this.  otherwise we end up with warnings that can (should) be ignored
> >> when tmpfs is being emulated with ramfs.
> >
> > We may change the "ramfs:" accordingly. But *silently* ignoring
> > options is bad anyway?
> 
> i really hate nitpicking such minor shit, but reality is that output
> displayed in the kernel log that is incorrect is going to cause me
> grief via customer support, updating documentation, adding FAQs,
> etc... and i doubt i'm the only one here.

I don't think the message is "incorrect" - it is reminding user the fact.

But I didn't know that ignorant users will ask you for customer
support on the "new" warning. Sorry.

> my requirement is simple: valid tmpfs options should be silently
> consumed (i.e. ignored) when tmpfs is being emulated by ramfs (i.e.
> CONFIG_SHMEM=n).
> 
> so how about:
> default:
>     if (!strcmp(sb->s_id, "ramfs"))
>         printk(KERN_WARNING "%s: ignoring mount option: %s\n", sb->s_id, p);
>     break;

This is going overly complex, maybe we just revert to Hugh's original
patch for *complete* compatibility? Sorry for making a fuss.

Thanks,
Fengguang
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