linux-kernel - Re: [Virtio-fs] [PATCH 3/2] fs: simplify get_filesystem_list / get_all_fs

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Message-ID: <20210630173358.GD75386@redhat.com>
Date:   Wed, 30 Jun 2021 13:33:58 -0400
From:   Vivek Goyal <vgoyal@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Stefan Hajnoczi <stefanha@...hat.com>, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, virtio-fs@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [Virtio-fs] [PATCH 3/2] fs: simplify get_filesystem_list /
 get_all_fs_names

On Wed, Jun 30, 2021 at 07:36:01AM +0200, Christoph Hellwig wrote:
> On Tue, Jun 29, 2021 at 04:50:48PM -0400, Vivek Goyal wrote:
> > May be we should modify mount_block_root() code so that it does not
> > require that extra "\0". Possibly zero initialize page and that should
> > make sure list_bdev_fs_names() does not have to worry about it.
> > 
> > It is possible that a page gets full from the list of filesystems, and
> > last byte on page is terminating null. In that case just zeroing page
> > will not help. We can keep track of some sort of end pointer and make
> > sure we are not searching beyond that for valid filesystem types.
> > 
> > end = page + PAGE_SIZE - 1;
> > 
> > mount_block_root()
> > {
> > 	for (p = fs_names; p < end && *p; p += strlen(p)+1) {
> > 	}
> > }
> 
> Maybe.  To honest I'd prefer to not even touch this unrelated code given
> how full of landmines it is :)

Agreed. It probably is better to make such changes incrementally. 

Given third patch is nice to have cleanup kind of thing, can we first
just merge first two patches to support non-block device filesystems as
rootfs.

We will really like to have a method to properly boot virtiofs as rootfs.

Thanks
Vivek