linux-ext4 - Re: Sign, more experimentation and broken features...

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Message-ID: <20130312120425.4665.qmail@science.horizon.com>
Date:	12 Mar 2013 08:04:25 -0400
From:	"George Spelvin" <linux@...izon.com>
To:	linux@...izon.com, tytso@....edu
Cc:	linux-ext4@...r.kernel.org
Subject: Re: Sign, more experimentation and broken features...

> I'm going to guess there may be problems with using the e2fsck -D
> option with bigalloc.  I could imagine potential problems with that,
> and it's probably not something we've explicitly tested. 

Ah.  I'll see if I can re-create and test that.

> Also, just to check.... all of this was done with the file system
> unmounted, right?

Definitely.  I would hope the lack of error message from e2fsck
made that clear, but I suppose it could have been mounted RO.

> The good news is that this appears to be a newly added group, so
> hopefully there was no data lost.

I noticed that, too.  I also have the ability to leave this FS alone for
a while, so I haven't touched it yet.  Is there some more useful debug
information to be gathered before I start contaminating the scene?

> It may be worth mounting the file system read-only and copying all of
> your data off before you do anything else....

Yeah, I'll have to borrow some additional drives to do that with...

> Also, it looks like there may be some problems with the metadata_csum
> option when resizing, either alone or in combination with bigalloc.
> Please note that I have ___not___ really done a lot of exhaustive
> testing with metadata_csum, since it's not in a released final state
> in e2fsprogs, and I've had lots of other things I've been busy trying
> to make sure is stablized.  For example, we are still working on
> fixing various test failures with bigalloc.  It's probably good enough
> for fairly simple workloads (mostly using fallocate and direct I/O),
> but there are corner cases which we are still working on fixing.

I've jyst been running it successfully on a few machines since my last round
of complaints, so I figured I'd try a *new* feature as well.  :-)

(I would have turned on INLINE_DATA too if I could figure out how to
enable it.  Ah, -O inline_data seems to be it.)

Unfortunately, I was stupid and didn't grab the latest e2fsprogs that
includes the bigalloc warnings.
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