linux-ext4 - Re: ext2_block_alloc

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Date:	Tue, 23 Dec 2008 01:05:45 -0700
From:	Andreas Dilger <adilger@....com>
To:	Sandeep K Sinha <sandeepksinha@...il.com>
Cc:	Peter Teoh <htmldeveloper@...il.com>,
	Mike Snitzer <snitzer@...il.com>,
	Rohit Sharma <imreckless@...il.com>,
	Kernelnewbies <kernelnewbies@...linux.org>,
	ext4 <linux-ext4@...r.kernel.org>
Subject: Re: ext2_block_alloc_info

On Dec 23, 2008  10:07 +0530, Sandeep K Sinha wrote:
> I have a tool ready with unfolds a file system completely thrugh
> ioctl. You will just have to patch the kernel.
> And that also, its for ext2.

It would be much more generic to use the FIEMAP ioctl, which has made
it into the 2.6.28 kernel.  It will currently only dump the file data
and xattr blocks, but it is designed to be extensible to allow dumping
other kinds of inode metadata (e.g. indirect/index blocks, etc).

> But its really verbose.

There are patches to e2fsprogs to allow filefrag to call FIEMAP to dump
the file layout.  They were posted to this list a few months ago, and
are scheduled for upstream inclusion.  While they will be part of e2fsprogs,
the FIEMAP ioctl is a generic mechanism that is supported by ext2/3/4,
OCFS, and XFS, and hopefully more now that it is in the kernel.

> You can have a look for the sources @ http://code.google.com/p/fscops/
> We will be uploading the tool there soon.

While the description of "What OHSM offer" sounds really good, I couldn't
find any code or description of what is actually implemented.  Is this
a system that actually works, or is it only describing what you would like
OHSM to do?

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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