From: Vlastimil Babka <vbabka@suse.cz>
To: Vitaly Kuznetsov <vkuznets@redhat.com>, linux-mm@kvack.org
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
Stephen Rothwell <sfr@canb.auug.org.au>,
Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] Revert "mm: rename _count, field of the struct page, to _refcount"
Date: Thu, 16 Jun 2016 11:36:47 +0200 [thread overview]
Message-ID: <d7049c89-7b78-ee1c-7216-90d8dd69d1b5@suse.cz> (raw)
In-Reply-To: <1466068966-24620-1-git-send-email-vkuznets@redhat.com>
On 06/16/2016 11:22 AM, Vitaly Kuznetsov wrote:
> _count -> _refcount rename in commit 0139aa7b7fa12 ("mm: rename _count,
> field of the struct page, to _refcount") broke kdump. makedumpfile(8) does
> stuff like READ_MEMBER_OFFSET("page._count", page._count) and fails. While
> it is definitely possible to fix this particular tool I'm not sure about
> other tools which might be doing the same.
>
> I suggest we remember the "we don't break userspace" rule and revert for
> 4.7 while it's not too late.
I don't think the rule applies to tools such as kdump and crash, or e.g.
systemtap, that interact with kernel internals even though they are
technically "userspace". They have to adapt to new kernel versions all
the time, the internal APIs are not frozen. Otherwise we would be quite
limited in evolving the kernel...
So even though the change in question is not essential (field rename)
and reverting wouldn't really hurt technical progress, this is not a
sufficient reason, IMO. Thus, NAK.
Vlastimil
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prev parent reply other threads:[~2016-06-16 9:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-16 9:22 Vitaly Kuznetsov
2016-06-16 9:32 ` Christoph Hellwig
2016-06-16 10:30 ` Vitaly Kuznetsov
2016-06-16 10:59 ` Michal Hocko
2016-06-16 11:22 ` Vitaly Kuznetsov
2016-06-16 11:28 ` Michal Hocko
2016-06-16 9:36 ` Vlastimil Babka [this message]
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