From: Alexander Aring <aahringo@redhat.com>
To: cluster-devel.redhat.com
Subject: [Cluster-devel] [PATCHv2 v6.5-rc1 3/3] fs: dlm: allow to F_SETLKW getting interrupted
Date: Fri, 14 Jul 2023 19:40:47 -0400 [thread overview]
Message-ID: <CAK-6q+gNoZw9HSWvKKb2jS1m4W-NxbrsrPE4x_DudmpHiAhw0w@mail.gmail.com> (raw)
In-Reply-To: <20230713164838.3583052-4-aahringo@redhat.com>
Hi,
On Thu, Jul 13, 2023 at 12:49?PM Alexander Aring <aahringo@redhat.com> wrote:
>
> This patch implements dlm plock F_SETLKW interruption feature. If the
> pending plock operation is not sent to user space yet it can simple be
> dropped out of the send_list. In case it's already being sent we need to
> try to remove the waiters in dlm user space tool. If it was successful a
> reply with DLM_PLOCK_OP_CANCEL optype instead of DLM_PLOCK_OP_LOCK comes
> back (flag DLM_PLOCK_FL_NO_REPLY was then being cleared in user space)
> to signal the cancellation was successful. If a result with optype
> DLM_PLOCK_OP_LOCK came back then the cancellation was not successful.
There is another use-case for this op that's only used kernel
internally by nfs. It's F_CANCELLK [0]. I will try to implement this
feature as I think the current behaviour is broken [1].
An unlock is not a revert and if the lock request is in waiting state,
unlocking will do exactly nothing.
I am still questioning how the API of [0] is supposed to work as [0]
does not evaluate any return value if it was successfully canceled or
not. Maybe they meant cancel and if it was not successful unlock it,
but an unlock is not a revert and posix locks support up/downgrade
locking e.g. read/write locks. However I think unlocking if
cancellation wasn't successful is meant here.
Besides that, I will change that DLM_PLOCK_OP_CANCEL will always
expect a reply back.
- Alex
[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/lockd/svclock.c#n705
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/gfs2/file.c?h=v6.5-rc1#n1439
prev parent reply other threads:[~2023-07-14 23:40 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-13 16:48 [Cluster-devel] [PATCHv2 v6.5-rc1 0/3] fs: dlm: workarounds and cancellation Alexander Aring
2023-07-13 16:48 ` [Cluster-devel] [PATCHv2 v6.5-rc1 1/3] fs: dlm: ignore DLM_PLOCK_FL_CLOSE flag results Alexander Aring
2023-07-13 16:48 ` [Cluster-devel] [PATCHv2 v6.5-rc1 2/3] fs: dlm: introduce DLM_PLOCK_FL_NO_REPLY flag Alexander Aring
2023-07-13 16:48 ` [Cluster-devel] [PATCHv2 v6.5-rc1 3/3] fs: dlm: allow to F_SETLKW getting interrupted Alexander Aring
2023-07-14 23:40 ` Alexander Aring [this message]
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