linux-kernel - Re: [PATCH 17/46] fs: Use rename lock and RCU for multi-step operations

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Message-ID: <AANLkTi=or1Ya21Am8Dr4KVHgqkwvNxFwgn407=wxRfVa@mail.gmail.com>
Date:	Tue, 25 Jan 2011 14:10:38 -0800
From:	Yehuda Sadeh Weinraub <yehudasa@...il.com>
To:	Nick Piggin <npiggin@...il.com>
Cc:	Nick Piggin <npiggin@...nel.dk>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, Sage Weil <sage@...dream.net>,
	ceph-devel@...r.kernel.org
Subject: Re: [PATCH 17/46] fs: Use rename lock and RCU for multi-step operations

On Wed, Jan 19, 2011 at 2:32 PM, Nick Piggin <npiggin@...il.com> wrote:
> On Thu, Jan 20, 2011 at 9:27 AM, Yehuda Sadeh Weinraub
> <yehudasa@...il.com> wrote:
>> On Tue, Jan 18, 2011 at 2:42 PM, Nick Piggin <npiggin@...il.com> wrote:
>>> On Wed, Jan 19, 2011 at 9:32 AM, Yehuda Sadeh Weinraub
>>
>>>> There's an issue with ceph as it references the
>>>> dentry->d_parent(->d_inode) at dentry_release(), so setting
>>>> dentry->d_parent to NULL here doesn't work with ceph. Though there is
>>>> some workaround for it, we would like to be sure that this one is
>>>> really required so that we don't exacerbate the ugliness. The
>>>> workaround is to keep a pointer to the parent inode in the private
>>>> dentry structure, which will be referenced only at the .release()
>>>> callback. This is clearly not ideal.
>>>
>>> Hmm, I'll have to think about it. Probably we can check for
>>> d_count == 0 rather than parent != NULL I think?
>>>
>>
>> That'll solve ceph's problem, don't know about how'd affect other
>> stuff. We'll need to know whether this is the solution, or whether
>> we'd need to introduce some other band aid fix.
>
> No I think it will work fine. Basically we just need to know whether
> we have been deleted, and if so then we restart rather than walking
> back up the parent.
>
> I'll send a patch in a few days. For the meantime, it's a rathe
> small window for ceph to worry about. So we'll have something
> before -rc2 which should be OK.
>

I guess that it's a bit late for -rc2, should we assume that it'll be on -rc3?

Thanks,
Yehuda
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