From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH v3 01/39] fs: introduce a ->s_cdev field into struct
 super_block
Date: Sat, 3 Oct 2015 23:31:19 -0700
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To: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
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On Tue, Sep 15, 2015 at 05:01:56PM +0800, Dongsheng Yang wrote:
> There are some filesystems are running on char devs, such
> as ubifs. So we need a field in super_block to hold a
> reference to the char device.

We only care about the block device to get a device number to return
in st.st_dev.  And while filesystem literally run on top of a block
device that is not the case of a character device - you might use a
chardev to identify a device to mount but it'll never use the actual
char device.

So please don't bloat the superblock with this.