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From: Christian Schoenebeck <linux_oss@crudebyte.com>
To: Dominique Martinet <asmadeus@codewreck.org>
Cc: Nikolay Kichukov <nikolay@oldum.net>,
	v9fs-developer@lists.sourceforge.net, netdev@vger.kernel.org,
	Eric Van Hensbergen <ericvh@gmail.com>,
	Latchesar Ionkov <lucho@ionkov.net>, Greg Kurz <groug@kaod.org>,
	Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH v3 6/7] 9p/trans_virtio: support larger msize values
Date: Wed, 24 Nov 2021 13:22:20 +0100	[thread overview]
Message-ID: <2311686.9pNgMZ9BYA@silver> (raw)
In-Reply-To: <YZwbJiFcLgwITsUe@codewreck.org>

On Montag, 22. November 2021 23:35:18 CET Dominique Martinet wrote:
> Christian Schoenebeck wrote on Mon, Nov 22, 2021 at 02:32:23PM +0100:
> > I "think" this could be used for all 9p message types except for the
> > listed
> > former three, but I'll review the 9p specs more carefully before v4. For
> > Tread and Twrite we already received the requested size, which just
> > leaves Treaddir, which is however indeed tricky, because I don't think we
> > have any info how many directory entries we could expect.
> 
> count in Treaddir is a number of bytes, not a number of entries -- so
> it's perfect for this as well :)

Yes it is in bytes, but it's currently always simply msize - P9_READDIRHDRSZ:
https://github.com/torvalds/linux/blob/5d9f4cf36721aba199975a9be7863a3ff5cd4b59/fs/9p/vfs_dir.c#L159

As my planned milestone for this series is max. 4 MB msize, it might be okay
for now, but it is something to keep in mind and should be checked whether it
will slow down things.

On the long term, when msize >4MB is supported, this definitely must be
addressed.

> > A simple compile time constant (e.g. one macro) could be used instead of
> > this function. If you prefer a constant instead, I could go for it in v4
> > of course. For this 9p client I would recommend a function though, simply
> > because this code has already seen some authors come and go over the
> > years, so it might be worth the redundant code for future safety. But
> > I'll adapt to what others think.
> 
> In this case a fallback constant seems simpler than a big switch like
> you've done, but honestly I'm not fussy at this point -- if you work on
> this you have the right to decide this kind of things in my opinion.
> 
> My worry with the snippet you listed is that you need to enumerate all
> calls again, so if someday the protocol is extended it'll be a place to
> forget adding new calls (although compiler warnings help with that),
> whereas a fallback constant will always work as long as it's small
> messages.
> 
> But really, as long as it's not horrible I'll take it :)

Maybe I can find a compromise. :)

Best regards,
Christian Schoenebeck



  reply	other threads:[~2021-11-24 12:28 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-22 16:00 [PATCH v3 0/7] net/9p: remove msize limit in virtio transport Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 1/7] net/9p: show error message if user 'msize' cannot be satisfied Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 2/7] 9p/trans_virtio: separate allocation of scatter gather list Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 3/7] 9p/trans_virtio: turn amount of sg lists into runtime info Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 4/7] 9p/trans_virtio: introduce struct virtqueue_sg Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 5/7] net/9p: add trans_maxsize to struct p9_client Christian Schoenebeck
2021-09-22 16:00 ` [PATCH v3 6/7] 9p/trans_virtio: support larger msize values Christian Schoenebeck
2021-11-20 11:20   ` Nikolay Kichukov
2021-11-20 11:45     ` Dominique Martinet
2021-11-20 14:46       ` Christian Schoenebeck
2021-11-20 21:28         ` Nikolay Kichukov
2021-11-20 23:02         ` Dominique Martinet
2021-11-21 16:57           ` Christian Schoenebeck
2021-11-21 22:12             ` Dominique Martinet
2021-11-22 13:32               ` Christian Schoenebeck
2021-11-22 22:35                 ` Dominique Martinet
2021-11-24 12:22                   ` Christian Schoenebeck [this message]
2021-09-22 16:00 ` [PATCH v3 7/7] 9p/trans_virtio: resize sg lists to whatever is possible Christian Schoenebeck

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