linux-ext4 - Re: [PATCH] mke2fs: use lazy inode init on some discard-able devices

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Message-Id: <D416033E-58F9-46F8-B8B0-546C949CB6BE@mit.edu>
Date:	Mon, 23 Aug 2010 06:49:22 -0400
From:	Theodore Tso <tytso@....EDU>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] mke2fs: use lazy inode init on some discard-able devices

On Aug 20, 2010, at 5:41 PM, Eric Sandeen wrote:

> If a device supports discard -and- returns 0s for discarded blocks,
> then we can skip the inode table initialization -and- the inode table
> zeroing at mkfs time, and skip the lazy init as well since they are
> already zeroed out.
> 
> Signed-off-by: Eric Sandeen <sandeen@...hat.com>

This needs to be configurable in /etc/mke2fs.conf.  Without naming
the manufacturer, I'm aware of at least one device which claims 
that discard works, and will even return zeros --- but after a
power cycle, if the block has not been reallocated, will once again
return the old, pre-discard values that had been stored in that block.

In other words, the discard is not power-cycle persistent...

-- Ted

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