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Date:   Tue, 20 Aug 2019 14:22:13 +0800
From:   Gao Xiang <gaoxiang25@huawei.com>
To:     Qu Wenruo <quwenruo.btrfs@gmx.com>
CC:     <miaoxie@huawei.com>, Gao Xiang <hsiangkao@aol.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Jan Kara <jack@suse.cz>, Christoph Hellwig <hch@infradead.org>,
        Amir Goldstein <amir73il@gmail.com>,
        Dave Chinner <david@fromorbit.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        devel <devel@driverdev.osuosl.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Richard Weinberger <richard@nod.at>,
        Eric Biggers <ebiggers@kernel.org>,
        "Chao Yu" <yuchao0@huawei.com>,
        linux-erofs <linux-erofs@lists.ozlabs.org>,
        Al Viro <viro@zeniv.linux.org.uk>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        "Theodore Y. Ts'o" <tytso@mit.edu>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "David Sterba" <dsterba@suse.cz>,
        Li Guifu <bluce.liguifu@huawei.com>,
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        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] erofs: move erofs out of staging
Message-ID: <20190820062213.GA202784@architecture4>
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Hi Qu,

On Tue, Aug 20, 2019 at 02:04:46PM +0800, Qu Wenruo wrote:
> [...]
> 
> And performance is another point.
> That tree-checker in btrfs is as fast/slow as CRC32.
> Not sure how it would be for dm-verity, but I guess it's slower than
> CRC32 if using any strong hash.

Just a word, dm-verity can do simple CRC32 without hash
tree in priciple as well. It is only a time problem.

> 
> Anyway, for a RO fs, if it's relying on dm-verify then that's OK for
> real-world usage.
> But as a standalone fs, even it's RO, a verification layer would be a
> great plus.

Yes, again, it's on my schedule at least.

> 
> At least when new student developers try fuzzed images on the fs, it
> would be a good surprise other than tons of new bug reports.
> 
> > 
> >  
> >>>
> [...]
> >>>
> >>> Yes, we will do such a debugging tool of course. Actually Li Guifu is now
> >>> developping a erofs-fuse to support old linux versions or other OSes for
> >>> archiveing only use, we will base on that code to develop a better fuzzer
> >>> tool as well.
> >>
> >> Personally speaking, debugging tool is way more important than a running
> >> kernel module/fuse.
> >> It's human trying to write the code, most of time is spent educating
> >> code readers, thus debugging tool is way more important than dead cold code.
> > 
> > Agree, Xiang and I have no time to developing this feature now, we are glad very much if you could help
> > us to do it ;)
> 
> In fact, since the fs is a RO fs, it could be pretty good educational
> example for any fs newbies. Thus a debug tool which can show the full
> metadata of the fs can really be helpful.

Yes, I think EROFS will be helpful for all fs newbies to understand
the basic fs concepts, and I have received contributions from some
new kernel developers. And again, I will do in my spare time.

I'm dedicated to playing with EROFS in my spare time (rather than
only at work to maintain for our products), so I will do and don't
worry about that.

And I agree with Miao Xie on one word, you can join us as well for
educational reason or whatever if you have some extra time... :)

Thanks,
Gao Xiang

> 
> In fact, btrfs-debug-tree (now "btrfs ins dump-tree") leads my way to
> btrfs, and still one of my favourite tool to debug.
> 
> Thanks,
> Qu
> 
> 


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