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Date:   Thu, 9 Aug 2018 03:18:28 +0200
From:   Dominique Martinet <asmadeus@codewreck.org>
To:     piaojun <piaojun@huawei.com>
Cc:     "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        Eric Van Hensbergen <ericvh@gmail.com>,
        Ron Minnich <rminnich@sandia.gov>,
        Latchesar Ionkov <lucho@ionkov.net>,
        Greg Kurz <groug@kaod.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        v9fs-developer@lists.sourceforge.net
Subject: Re: [PATCH] net/9p/trans_virtio.c: decrease the refcount of 9p
 virtio device when removing it
Message-ID: <20180809011828.GA2966@nautica>
References: <5B6AA65E.3030907@huawei.com>
 <20180808083630.GB16121@nautica>
 <5B6AB081.6090608@huawei.com>
 <20180808094014.GA5585@nautica>
 <5B6B8E96.9070302@huawei.com>
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piaojun wrote on Thu, Aug 09, 2018:
> > What exact kernel commit are you running?
>
> My kernel commit id 6edf1d4cb0acde, and I replace the 9p code with
> 9p-next. And I wonder if this will work well?

That is somewhere on top of 4.18-rc1 and got merged in 4.18-rc4, which
are close enough so while I can question the practice I don't see why
not.

I've just tried the following:
$ git checkout 6edf1d4cb0acde
$ git checkout martinetd/9p-next net/9p fs/9p include/net/9p
(martinetd/9p-next is 9f961802a7 as of this mail)
<make, install, reboot>
$ uname -r
4.18.0-rc1+
$ lsmod | grep -E '^9pnet_virtio' || echo "not loaded"
9pnet_virtio           32768  0
$ sudo modprobe -r 9pnet_virtio
$ lsmod | grep -E '^9pnet_virtio' || echo "not loaded"
not loaded
$ sudo modprobe 9pnet_virtio
$ sudo mount -t 9p -o debug=1,trans=virtio shm /mnt
$ ls /mnt
<stuff>
$ cat /sys/module/9pnet_virtio/drivers/virtio\:9pnet_virtio/*/mount_tag
tmpshm (these could use a new line...)
$ sudo umount /mnt
$ sudo modprobe -r 9pnet_virtio
$ lsmod | grep -E '^9pnet_virtio' || echo "not loaded"
not loaded

The /sys/devices/pci*/*/virtio*/mount_tag files are also removed
properly; I don't see any problem.


Not being able to reproduce is fine in general, but I also get problems
when applying the patch and unloading the module multiple times so I
can't help but question this patch and think your problem lies somewhere
else.

-- 
Dominique