LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Arnd Bergmann <arnd@arndb.de>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	dm-devel@redhat.com, linux-kernel@vger.kernel.org,
	Milan Broz <mbroz@redhat.com>, Guido Guenther <agx@sigxcpu.org>,
	Kevin Corry <kevcorry@us.ibm.com>,
	stable@kernel.org
Subject: Re: [2.6.24 PATCH 02/25] dm io:ctl use constant struct size
Date: Mon, 15 Oct 2007 09:34:09 +0200	[thread overview]
Message-ID: <200710150934.09842.arnd@arndb.de> (raw)
In-Reply-To: <20071015012621.GD10006@agk.fab.redhat.com>

On Monday 15 October 2007, Alasdair G Kergon wrote:
> The underlying ABI is not changing, I hope - the trailing padding in the
> struct should not affect the processing of the data by dm, and I see no
> reason to continue maintaining the fiction that the 32-bit and 64-bit
> ioctls are in some way incompatible with each other when they aren't
> AFAIK.

It's a corner case of some sort, as DM uses ioctl numbers differently
from most subsystems by splitting to code from the size argument
during processing. Your change is certainly not an _incompatible_
change to the ABI, but 32 bit binaries compiled against the new
headers will use different ioctl numbers from those built against
older headers.

This may break other code that expects a specific number, even
if your handler does not care. The old compat code handles both
variants (no variable size arguments), but /usr/bin/strace may have
encoded only one set of numbers AFAICT.

> And yes, a follow-up patch can clean up our use of the compatibility
> mechanism, going a little bit further than the patch you attached, I
> hope.

Ok, sounds good. I don't think it's the kind of patch that should go
into stable backports though.

	Arnd <><

  reply	other threads:[~2007-10-15  7:35 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-10-12 17:05 Alasdair G Kergon
2007-10-12 22:16 ` Arnd Bergmann
2007-10-15  1:26   ` Alasdair G Kergon
2007-10-15  7:34     ` Arnd Bergmann [this message]
2007-11-13 22:22       ` [stable] " Greg KH

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=200710150934.09842.arnd@arndb.de \
    --to=arnd@arndb.de \
    --cc=agx@sigxcpu.org \
    --cc=dm-devel@redhat.com \
    --cc=kevcorry@us.ibm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mbroz@redhat.com \
    --cc=stable@kernel.org \
    --cc=torvalds@linux-foundation.org \
    --subject='Re: [2.6.24 PATCH 02/25] dm io:ctl use constant struct size' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).