linux-kernel - Re: [PATCH] sysfs: return correct error code on unimplemented mmap()

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Message-ID: <20131029230524.GA14393@kroah.com>
Date:	Tue, 29 Oct 2013 16:05:24 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sysfs: return correct error code on unimplemented mmap()

On Mon, Oct 28, 2013 at 07:22:47PM +0200, Vladimir Zapolskiy wrote:
> On 10/28/13 18:35, Greg Kroah-Hartman wrote:
> >On Mon, Oct 28, 2013 at 06:28:30PM +0200, Vladimir Zapolskiy wrote:
> >>Both POSIX.1-2008 and Linux Programmer's Manual have a dedicated return
> >>error code for a case, when a file doesn't support mmap(), it's ENODEV.
> >>
> >>This change replaces overloaded EINVAL with ENODEV in a situation
> >>described above for sysfs binary files.
> >>
> >>Signed-off-by: Vladimir Zapolskiy<vladimir_zapolskiy@...tor.com>
> >>Cc: Greg Kroah-Hartman<gregkh@...uxfoundation.org>
> >
> >Is this a problem in linux-next or 3.12-rc7 and older kernels?  What
> >userspace tool is breaking here?
> 
> The patch itself is against 3.12-rc7, but the same problem can be found
> in older kernels as well.
> 
> I assume the bugfix is quite safe, because both EINVAL and ENODEV should
> be handled by user space tools, however for developers it might be
> beneficial to distinguish cases of completely not supported mmap() and
> supported but misused mmap() applied to a binary sysfs file. At the
> moment from the user space perspective there is no indication of
> unsupported mmap() over a file in sysfs.

Ok, fair enough, but it doesn't apply to my tree given the recent sysfs
changes there.  Can you redo this against linux-next, or wait for
3.13-rc1 and resend it against that release in a few weeks?

thanks,

greg k-h
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