linux-ext4 - Re: [PATCH] mke2fs: restore verbose message for BLKDISCARD

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Message-ID: <513DE554.6020508@redhat.com>
Date:	Mon, 11 Mar 2013 09:08:20 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
CC:	Stephen Warren <swarren@...dotorg.org>,
	Lukáš Czerner 
	<lczerner@...hat.com>, Chris Ball <cjb@...top.org>,
	linux-ext4@...r.kernel.org, Stephen Warren <swarren@...dia.com>
Subject: Re: [PATCH] mke2fs: restore verbose message for BLKDISCARD

On 3/8/13 1:00 PM, Theodore Ts'o wrote:
> I hate to suggest this, but there's so many crappy devices out there
> that I'm wondering if we need to figure out some way of maintaining a
> black list of devices that don't handle discard properly.  For
> example, the Sandisk U100 advertises a max discard granularity of 512
> bytes, but I've been advised that if you don't use a discard
> granularity of 256k, aligned on 256k, you'll be very, very, sorry.

> It sounds like Stephen's device is probably an example of Yet Another
> Busted Trim implementation.  The problem is that manufacturers will be
> releasing more broken products faster than we can update a blacklist
> in the kernel.  So any blacklist would have to be maintained online on
> the web, and dynamically updated by distro installers.   :-(

Yeah I think it may be time for a blacklist.

TBH I think we should revisit discard-at-mkfs-time by default as well.

It seemed like a decent idea at the time, but now we have handy
fstrim as well as online/dynamic/realtime trim, and trim at mkfs
makes mke2fs completely un-doable in the event of fat fingers.

-Eric


> 
>     	     		 	    	   		 - Ted
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