From: "J. Bruce Fields" <bfields@fieldses.org>
To: "J. Bruce Fields" <bfields@redhat.com>
Cc: linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org
Subject: Re: [RFC PATCH 0/6] Fix NFSv4 delegations
Date: Fri, 3 Feb 2012 15:58:18 -0500 [thread overview]
Message-ID: <20120203205818.GE2999@fieldses.org> (raw)
In-Reply-To: <1326816029-13913-1-git-send-email-bfields@redhat.com>
On Tue, Jan 17, 2012 at 11:00:23AM -0500, J. Bruce Fields wrote:
> From: "J. Bruce Fields" <bfields@redhat.com>
>
> NFSv4 delegations are currently implemented as leases. However, leases
> don't have quite the same semantics, which means that delegations are
> currently enforced correctly only for conflicts between NFSv4 clients.
>
> I previously attempted to address this by "fixing" the existing lease
> behavior, assuming it was a bug--but from further investigation it looks
> like that would be the wrong thing to do for Samba.
>
> So instead I'm defining a new FL_DELEG flag to mark NFSv4 delegations,
> and varying behavior based on that. Delegations aren't meant to be
> available to userspace for now--nfsd is the only user.
>
> In theory this code allows both read and write delegations, but I'm only
> using read delegations for now--write delegations are a project for
> another day. (At which point write leases will probably need some
> fixing while we're at it.)
>
> Still to do: if OPEN(dirfd, name) returns a delegation to the client,
> then the client should be guaranteed that the opened file is still
> linked as (dirfd, name). But the current nfsd code allows a rename or
> unlink to intervene between the lookup and the request for a delegation.
OK, I decided I could fix that in the nfsd4 open code by retrying the
lookup after obtaining the delegation, and just dropping the delegation
(they're always optional) if it turned out there'd been a race.
I'll post revised vfs patches (without that extra nfsd stuff).
--b.
next prev parent reply other threads:[~2012-02-03 20:58 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-17 16:00 [RFC PATCH 0/6] Fix NFSv4 delegations J. Bruce Fields
2012-01-17 16:00 ` [RFC PATCH 1/6] locks: introduce new FL_DELEG lock flag J. Bruce Fields
2012-01-17 16:00 ` [RFC PATCH 2/6] locks: give break_lease its own flags J. Bruce Fields
2012-01-17 16:17 ` Bypass encrypt and decrypt data in dm-crypt Fan Zhang
2012-01-17 16:00 ` [RFC PATCH 3/6] locks: break delegations on unlink J. Bruce Fields
2012-01-17 16:00 ` [RFC PATCH 4/6] locks: break delegations on rename J. Bruce Fields
2012-01-17 16:00 ` [RFC PATCH 5/6] locks: break delegations on any attribute modification J. Bruce Fields
2012-01-17 16:00 ` [RFC PATCH 6/6] locks: break delegations on link J. Bruce Fields
2012-02-03 20:58 ` J. Bruce Fields [this message]
2012-02-03 21:09 ` Provide vfs support for NFSv4 delegations J. Bruce Fields
2012-02-03 21:09 ` [PATCH 1/6] locks: introduce new FL_DELEG lock flag J. Bruce Fields
2012-02-03 21:09 ` [PATCH 2/6] locks: give break_lease its own flags J. Bruce Fields
2012-02-03 21:09 ` [PATCH 3/6] locks: break delegations on unlink J. Bruce Fields
2012-02-03 21:09 ` [PATCH 4/6] locks: break delegations on rename J. Bruce Fields
2012-02-03 21:09 ` [PATCH 5/6] locks: break delegations on any attribute modification J. Bruce Fields
2012-02-03 21:09 ` [PATCH 6/6] locks: break delegations on link J. Bruce Fields
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