Subject: Re: About the try to remove cross-release feature entirely by Ingo
To: Theodore Ts'o <tytso@mit.edu>,
        Matthew Wilcox <willy@infradead.org>,
        Byungchul Park <max.byungchul.park@gmail.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>, david@fromorbit.com,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Amir Goldstein <amir73il@gmail.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        oleg@redhat.com, kernel-team@lge.com, daniel@ffwll.ch
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From: Byungchul Park <byungchul.park@lge.com>
Message-ID: <f2bc220a-a363-122a-dbf9-e5416c550899@lge.com>
Date: Wed, 3 Jan 2018 11:10:37 +0900
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On 12/31/2017 7:40 AM, Theodore Ts'o wrote:
> On Sat, Dec 30, 2017 at 12:44:17PM -0800, Matthew Wilcox wrote:
>>
>> I'm not sure I agree with this part.  What if we add a new TCP lock class
>> for connections which are used for filesystems/network block devices/...?
>> Yes, it'll be up to each user to set the lockdep classification correctly,
>> but that's a relatively small number of places to add annotations,
>> and I don't see why it wouldn't work.
> 
> I was exagerrating a bit for effect, I admit.  (but only a bit).
> 
> It can probably be for all TCP connections that are used by kernel
> code (as opposed to userspace-only TCP connections).  But it would
> probably have to be each and every device-mapper instance, each and
> every block device, each and every mounted file system, each and every
> bdi object, etc.
> 
> The point I was trying to drive home is that "all we have to do is
> just classify everything well or just invalidate the right lock

Just to be sure, we don't have to invalidate lock objects at all but
a problematic waiter only.

> objects" is a massive understatement of the complexity level of what
> would be required, or the number of locks/completion handlers that
> would have to be blacklisted.
> 
> 						- Ted
> 

-- 
Thanks,
Byungchul