lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite for Android: free password hash cracker in your pocket
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Wed, 13 Dec 2006 07:36:29 -0600
From:	Dave Kleikamp <>
To:	"Amit K. Arora" <>
Cc:	Mingming Cao <>,,,
Subject: Re: [RFC][Patch 1/1] Persistent preallocation in ext4

On Wed, 2006-12-13 at 15:31 +0530, Amit K. Arora wrote:
> On Tue, Dec 12, 2006 at 04:20:38PM -0800, Mingming Cao wrote:
> > On Tue, 2006-12-12 at 11:53 +0530, Amit K. Arora wrote:

> > Supporting preallocation for extent based files seems fairly
> > straightforward.  I agree we should look at this first.  After get this
> > done, it probably worth re-consider whether to support preallocation for
> > non-extent based files on ext4. I could imagine user upgrade from ext3
> > to ext4, and expecting to use preallocation on those existing files....

I disagree here.  Why add the complexity for what is going to be a rare
case?  In cases where a user is going to benefit from preallocation,
she'll probably also benefit from extents, and would be better off
making a copy of the file, thus converting it to extents.

> I gave a thought on this initially. But, I was not sure how we should
> implement preallocation in a non-extent based file. Using extents we can
> mark a set of blocks as unitialized, but how will we do this for
> non-extent based files ? If we do not have a way to mark blocks
> uninitialized, when someone will try to read from a preallocated block,
> it will return junk/stale data instead of zeroes.

If anything, the block-based preallocation could initialize all of the
data to zero.  It would be slow, but it would still provide the correct
function and result in contiguous allocation.

David Kleikamp
IBM Linux Technology Center

To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to
More majordomo info at

Powered by blists - more mailing lists