From: Theodore Ts'o <tytso@mit.edu>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: linux-ext4 <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH] ext4: Prevent massive fs corruption if verifying the block bitmap fails
Date: Wed, 17 Jul 2013 15:55:03 -0400 [thread overview]
Message-ID: <20130717195503.GC26859@thunk.org> (raw)
In-Reply-To: <20130717194356.GB5790@blackbox.djwong.org>
On Wed, Jul 17, 2013 at 12:43:56PM -0700, Darrick J. Wong wrote:
> I also wrote a script that fills a fs, maliciously marks all the fs metadata
> blocks as free, and writes more files to the fs, with the result that you
> corrupt the metadata. I wonder if it's feasible to modify mballoc to check
> that it's not handing out well known metadata locations to files?
We have that --- it's the block_validity mount option. I use it
regularly for testing. It's off by default because it does take a bit
more CPU time for every single block allocation and deallocation. It
would be useful if someone who had access to fast PCIe-attached flash
tried to measure the CPU utilization of a metadata-intensive workload
(such as fs_mark) with and without block_validity. If the overhead is
negligible, we could enable this by default, and remove the mount
option.
- Ted
next prev parent reply other threads:[~2013-07-17 19:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-17 2:02 [PATCH] ext4: Prevent massive fs corruption if verifying the block bitmap fails Darrick J. Wong
2013-07-17 3:08 ` Theodore Ts'o
2013-07-17 7:09 ` Darrick J. Wong
2013-07-17 13:19 ` Theodore Ts'o
2013-07-17 19:43 ` Darrick J. Wong
2013-07-17 19:55 ` Theodore Ts'o [this message]
2013-07-18 0:13 ` Darrick J. Wong
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