From: Trond Myklebust <trondmy@kernel.org>
To: Guillaume Nault <gnault@redhat.com>,
Christoph Hellwig <hch@infradead.org>
Cc: Trond Myklebust <trond.myklebust@hammerspace.com>,
Anna Schumaker <anna@kernel.org>,
Chuck Lever <chuck.lever@oracle.com>,
Jeff Layton <jlayton@kernel.org>,
linux-nfs@vger.kernel.org, Paolo Abeni <pabeni@redhat.com>,
Benjamin Coddington <bcodding@redhat.com>
Subject: Re: [PATCH v2] sunrpc: Use GFP_NOFS to prevent use of current->task_frag.
Date: Tue, 11 Oct 2022 11:57:53 -0400 [thread overview]
Message-ID: <a0bf0d49a7a69d20cfe007d66586a2649557a30b.camel@kernel.org> (raw)
In-Reply-To: <20221011150057.GB3606@localhost.localdomain>
On Tue, 2022-10-11 at 17:00 +0200, Guillaume Nault wrote:
> On Mon, Oct 10, 2022 at 11:18:19PM -0700, Christoph Hellwig wrote:
> > On Mon, Oct 10, 2022 at 06:56:50PM +0200, Guillaume Nault wrote:
> > > That's what my RFC patch did. It was rejected because reading
> > > current->flags may incur a cache miss thus slowing down TCP fast
> > > path.
> > > See the discussion in the Link tag:
> > > https://lore.kernel.org/netdev/b4d8cb09c913d3e34f853736f3f5628abfd7f4b6.1656699567.git.gnault@redhat.com/
> >
> > As GFP_NOFS/NOIO are on their way out the networking people will
> > have to
> > do this anyway.
>
> We can always think of a nicer solution in the future. But right now
> we
> have a real bug to fix.
>
> Commit a1231fda7e94 ("SUNRPC: Set memalloc_nofs_save() on all
> rpciod/xprtiod jobs") introduces a bug that crashes the kernel. I
> can't
> see anything wrong with a partial revert.
>
How about instead just adding a dedicated flag to the socket that
switches between the two page_frag modes?
That would remain future proofed, and it would give kernel users a
lever with which to do the right thing without unnecessarily
constraining the allocation modes.
--
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com
next prev parent reply other threads:[~2022-10-11 15:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-10 11:41 [PATCH v2] sunrpc: Use GFP_NOFS to prevent use of current->task_frag Guillaume Nault
2022-10-10 14:55 ` Christoph Hellwig
2022-10-10 16:56 ` Guillaume Nault
2022-10-11 6:18 ` Christoph Hellwig
2022-10-11 15:00 ` Guillaume Nault
2022-10-11 15:57 ` Trond Myklebust [this message]
2022-10-11 21:14 ` Guillaume Nault
2022-10-13 12:18 ` Guillaume Nault
2022-10-25 11:15 ` Guillaume Nault
2022-12-07 11:47 ` Benjamin Coddington
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