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From:   Chuck Lever III <chuck.lever@oracle.com>
To:     Leon Romanovsky <leon@kernel.org>, Jason Gunthorpe <jgg@nvidia.com>
CC:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
Subject: Re: [PATCH v1] RDMA/core: Fix check_flush_dependency splat on addr_wq
Thread-Topic: [PATCH v1] RDMA/core: Fix check_flush_dependency splat on
 addr_wq
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Date:   Wed, 24 Aug 2022 14:09:52 +0000
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> On Aug 24, 2022, at 5:20 AM, Leon Romanovsky <leon@kernel.org> wrote:
>=20
> On Tue, Aug 23, 2022 at 01:58:44PM +0000, Chuck Lever III wrote:
>>=20
>>=20
>>> On Aug 23, 2022, at 4:09 AM, Leon Romanovsky <leon@kernel.org> wrote:
>>>=20
>>> On Mon, Aug 22, 2022 at 11:30:20AM -0400, Chuck Lever wrote:
>=20
> <...>
>=20
>>>> The xprtiod work queue is WQ_MEM_RECLAIM, so any work queue that
>>>> one of its work items tries to cancel has to be WQ_MEM_RECLAIM to
>>>> prevent a priority inversion.
>>>=20
>>> But why do you have WQ_MEM_RECLAIM in xprtiod?
>>=20
>> Because RPC is under a filesystem (NFS). Therefore it has to handle
>> writeback demanded by direct reclaim. All of the storage ULPs have
>> this constraint, in fact.
>=20
> I don't know, this ib_addr workqueue is used when connection is created.

Reconnection is exactly when we need to ensure that creating
a new connection won't trigger more memory allocation, because
that will immediately deadlock.

Again, all network storage ULPs have this constraint.


> Jason, what do you think?
>=20
> Thanks

--
Chuck Lever