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From: David Howells <dhowells@redhat.com>
In-Reply-To: <1726980.McBZPkGeyK@silver>
References: <1726980.McBZPkGeyK@silver> <20240129115512.1281624-1-dhowells@redhat.com>
To: Christian Schoenebeck <linux_oss@crudebyte.com>
Cc: dhowells@redhat.com, Eric Van Hensbergen <ericvh@kernel.org>,
    Dominique Martinet <asmadeus@codewreck.org>,
    Latchesar Ionkov <lucho@ionkov.net>,
    Matthew Wilcox <willy@infradead.org>,
    Jeff Layton <jlayton@kernel.org>,
    Christian Brauner <christian@brauner.io>, netfs@lists.linux.dev,
    v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org,
    linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/3] 9p: Further netfslib-related changes
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Date: Mon, 29 Jan 2024 14:22:15 +0000
Message-ID: <1400271.1706538135@warthog.procyon.org.uk>

Christian Schoenebeck <linux_oss@crudebyte.com> wrote:

> >  (1) Enable large folio support for 9p.  This is handled entirely by
> >      netfslib and is already supported in afs.  I wonder if we should =
limit
> >      the maximum folio size to 1MiB to match the maximum I/O size in t=
he 9p
> >      protocol.
> =

> The limit depends on user's 'msize' 9p client option and on the 9p trans=
port
> implementation. The hard limit with virtio transport for instance is cur=
rently
> just 500k (patches for virtio 4MB limit fetching dust unfortunately).

Okay.  Is that 500KiB or 512Kib?

> Would you see an advantage to limit folio size? I mean p9_client_read() =
etc.
> are automatically limiting the read/write chunk size accordingly.

For reads not so much, but for writes it would mean that a dirty folio is
either entirely written or entirely failed.  I don't know how important th=
is
would be for the 9p usecases.

David