linux-kernel - Re: [PATCH V3 4/4] 9p: convert to the new mount API

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Message-ID: <aTBTndsQaLAv0sHP@codewreck.org>
Date: Thu, 4 Dec 2025 00:13:33 +0900
From: Dominique Martinet <asmadeus@...ewreck.org>
To: Eric Sandeen <sandeen@...hat.com>
Cc: Remi Pommarel <repk@...plefau.lt>, v9fs@...ts.linux.dev,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	ericvh@...nel.org, lucho@...kov.net, linux_oss@...debyte.com,
	eadavis@...com
Subject: Re: [PATCH V3 4/4] 9p: convert to the new mount API

Eric Sandeen wrote on Tue, Dec 02, 2025 at 04:12:36PM -0600:
> Working on this, but something that confuses me about the current
> (not for-next) code:
> 
> If I mount with "cache=loose" I see this in /proc/mounts:
> 
> 127.0.0.1 /mnt 9p rw,relatime,uname=fsgqa,aname=/tmp/9,cache=f,access=user,trans=tcp 0 0
> 
> note the "cache=f" thanks to show_options printing "cache=%x"
> 
> "mount -o cache=f" is rejected, though, because "f" is not a parseable
> number.
> 
> Shouldn't it be printing "cache=0xf" instead of "cache=f?"

Definitely should be!

> (for some reason, though, in my test "remount -o,ro" does still work even with
> "cache=f" in /proc/mounts but that seems to be a side effect of mount.9p trying
> to use the new mount API when it shouldn't, or ...???)

... and Remi explicitly had cache=loose in his command line, so I'm also
surprised it worked...

> I'll send my fix-up patch with a (maybe?) extra bugfix of printing
> "cache=0x%x" in show_options, and you can see what you think... it could
> be moved into a pure bugfix patch first if you agree.

Thank you! I would have been happy to see both together but it does make
more sense separately, I've just tested and pushed both your patches to
-next


I also agree the other show_options look safe enough as they either
print a string or int. . . .
Ah, actually I spotted another one:
        if (v9ses->debug)
                seq_printf(m, ",debug=%x", v9ses->debug);
This needs to be prefixed by 0x as well -- Eric, do you mind if I amend
your patch 5 with that as well?


Remi - I did check rootfstype=9p as well and all seems fine but I'd
appreciate if you could test as well


Thanks!
-- 
Dominique Martinet | Asmadeus