From: Al Viro <viro@ZenIV.linux.org.uk>
To: Daniel Ehrenberg <dehrenberg@google.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
Gwendal Grignou <gwendal@chromium.org>,
Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
Subject: Re: [RFC PATCH] vfs: Use 12:20 bit major:minor in stat everywhere
Date: Wed, 4 Mar 2015 01:22:12 +0000 [thread overview]
Message-ID: <20150304012211.GV29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CAAK6Zt27jsAv_z6DY+ozqv+nx5HvfY7tCe12WFUFQKsa9s-qQA@mail.gmail.com>
On Tue, Mar 03, 2015 at 05:10:22PM -0800, Daniel Ehrenberg wrote:
> > What's to guarantee that your ABI change won't break any of those?
>
> I guess it's impossible to guarantee, but if there is an error, it'll
> be that an -EOVERFLOW error is suppressed and the high bits of the
> major:minor pair are shaved off by the userspace program. I would
> suspect that this would just make debugging harder, rather than
> actually break an automated program which counts on getting EOVERFLOW
> from a huge block device, but no way to know. The block device has to
> actually exist for this to happen, and all we're talking about is stat
> failing. So it's replacing an an error code with erroneous way to get
> data about a device node (erroneous just because userspace ignores
> some of the bits with the answer).
All it takes is more than 16 SCSI disks, AFAICS, and use of open-coded
MINOR() somewhere in old userland code...
next prev parent reply other threads:[~2015-03-04 1:22 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-04 0:37 [RFC PATCH] vfs: Use 12:20 bit major:minor in stat everywhere Dan Ehrenberg
2015-03-04 0:53 ` Al Viro
2015-03-04 1:10 ` Daniel Ehrenberg
2015-03-04 1:22 ` Al Viro [this message]
2015-03-04 1:37 ` Gwendal Grignou
2015-03-04 1:47 ` Al Viro
2015-03-04 7:26 ` Gwendal Grignou
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