linux-kernel - Re: [PATCH] f2fs: introduce on-disk layout version checking functionality

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Message-ID: <20160523082542.GA27833@infradead.org>
Date:	Mon, 23 May 2016 01:25:42 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Viacheslav Dubeyko <slava@...eyko.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Jaegeuk Kim <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	Vyacheslav.Dubeyko@...t.com, Cyril.Guyot@...t.com,
	Adam.Manzanares@...t.com, Damien.LeMoal@...t.com
Subject: Re: [PATCH] f2fs: introduce on-disk layout version checking
 functionality

On Fri, May 20, 2016 at 11:30:43AM -0700, Viacheslav Dubeyko wrote:
> I am not sure that I follow to your point. The F2FS has "feature" field
> (__le32 feature) into on-disk superblock (struct f2fs_super_block). The
> suggested patch introduces the new F2FS_FEATURE_16TB_SUPPORT flag. And
> it looks like as your comment.

It does, but at the same time you also introduce a major version
superblock
field.

> So, necessary changes in on-disk layout for 16+TB volumes support will
> be incompatible with current available version of F2FS driver. It means
> that, anyway, we need to increase version of on-disk layout (major_ver
> of struct f2fs_super_block). The presence of superblock's version and
> F2FS_FEATURE_16TB_SUPPORT flag will be very useful for consistency
> checking by fsck tool.

Why is the feature not enough for that?