linux-ext4 - Re: [PATCH, RFC V3] ext4: limit block allocations for indirect-block files to

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Message-ID: <4AA96CB0.3090309@redhat.com>
Date:	Thu, 10 Sep 2009 16:16:32 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Andreas Dilger <adilger@....com>
CC:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH, RFC V3] ext4: limit block allocations for	indirect-block
 files to < 2^32

Andreas Dilger wrote:
> On Sep 10, 2009  11:02 -0500, Eric Sandeen wrote:
>> This patch limits such allocations to < 232, and adds
>> WARN_ONs (maybe should be BUG_ONs) if we do get blocks
>> larger than that.
> 
> Given that this may corrupt the filesystem (e.g. block
> 2^32 turning into block 0 and overwriting the superblock)
> I think a BUG_ON() is probably more appropriate.  This
> should only happen with software bugs, so it is more
> appropriate than ext4_error() I think.

Ok, fine by me.  I can send an update.

Any suggestions on the naming issues?  (what's the official name for a
"not-extent-based-file?")

I ran it a lot through a mkfs/mount/fsstress/unmount/fsck cycle, and all
seemed well.  mkfs was without extents, so I was thinking we were in
good shape.

However, Ric just ran a massive fs_mark test on a 60T filesystem that he
created with "mke2fs" (no extents and no journal - accidentally) and we
got no corruption even without this patch.

I need to see if a filesystem w/o the extents feature (at all, vs. some
old-format files on an extents fs) never even tries to allocate past
2^32; I didn't think so, but now not so sure.

I probably need to do more testing ...

-Eric
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