From: Nick Piggin <npiggin@gmail.com>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: "J. R. Okajima" <hooanon05@yahoo.co.jp>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: vfs-scale, d_revalidate from nfsd
Date: Fri, 14 Jan 2011 14:12:35 +1100 [thread overview]
Message-ID: <AANLkTi=H7Zhe4VMsh_tdrd7Atb9FX8j4AdiMNepXGsj9@mail.gmail.com> (raw)
In-Reply-To: <20110114030325.GU19804@ZenIV.linux.org.uk>
On Fri, Jan 14, 2011 at 2:03 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Fri, Jan 14, 2011 at 01:57:55PM +1100, Nick Piggin wrote:
>> On Fri, Jan 14, 2011 at 1:03 AM, J. R. Okajima <hooanon05@yahoo.co.jp> wrote:
>> >
>> > NFSD calls filesystem's ->d_revalidate() with the parameter nd == NULL.
>> > So every
>> > ? ? ? ?if (nd->flags & LOOKUP_RCU)
>> > ? ? ? ? ? ? ? ?return -ECHILD;
>> > code which was added to ->d_revalidate() of FS which supports NFS
>> > exporting will crash.
>> >
>> > If we rewrite it as
>> > ? ? ? ?if (nd && (nd->flags & LOOKUP_RCU))
>> > ? ? ? ? ? ? ? ?return -ECHILD;
>> > the problem may not occur.
>> > But I am not sure whether lookup_one_len() call in NFSD support rcu-walk.
>>
>> Ah, good catch.
>>
>> I'm going to change the d_revalidate API so it takes and inode and rcu-walk
>> flag parameter to make it easier for filesystems to implement rcu-walk.
>>
>> That will take care of this NULL nd case.
>
> Oh, for fuck sake... Would you at least mind posting your API change
> description to fsdevel before going for it?
Of course. I was discussing it with Miklos yesterday too, but haven't
finished getting a proposal together.
The main idea here would be to just pass in a flags parameter rather
thank poking in nd to get the rcu-walk status. That would solve this
problem and also avoid nd for most filesystems that don't care about
it.
> ->d_revalidate() is one sick puppy and it's intimately involved in atomic
> open rewrite. Please, *please* don't make that shit even messier...
Right, I did agree with Miklos that using nd for passing rcu-walk
status was going in the wrong direction with that API. Do you
agree?
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next prev parent reply other threads:[~2011-01-14 3:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-13 14:03 vfs-scale, d_revalidate from nfsd J. R. Okajima
2011-01-14 2:57 ` Nick Piggin
2011-01-14 3:03 ` Al Viro
2011-01-14 3:12 ` Nick Piggin [this message]
2011-01-14 3:20 ` Al Viro
2011-01-14 3:22 ` Al Viro
2011-01-14 3:29 ` Nick Piggin
2011-01-14 3:38 ` Al Viro
2011-01-15 3:47 ` J. R. Okajima
2011-01-15 18:11 ` Nick Piggin
2011-02-15 5:07 ` J. R. Okajima
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