linux-ext4 - Re: [PATCH 1/2] Add discard/nodiscard mount option for ext3

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Date:	Mon, 12 Jul 2010 18:15:23 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Lukas Czerner <lczerner@...hat.com>
cc:	Ric Wheeler <rwheeler@...hat.com>, Jan Kara <jack@...e.cz>,
	linux-ext4@...r.kernel.org, jmoyer@...hat.com, eshishki@...hat.com,
	sandeen@...hat.com
Subject: Re: [PATCH 1/2] Add discard/nodiscard mount option for ext3

On Mon, 12 Jul 2010, Lukas Czerner wrote:

> On Mon, 12 Jul 2010, Ric Wheeler wrote:
> 
> > On 07/12/2010 11:19 AM, Jan Kara wrote:
> > > > Those mount option has the same meaning as in ext4 file system. It
> > > > provide a way to enable/disable file system's trim support. The trim
> > > > support is off by default, thus nodiscard option is not actually
> > > > necessary.
> > >    I kind of miss why ext3 should have a 'discard' mount option. When
> > > user calls DISCARD ioctl on the filesystem, then he probably wants
> > > discard to be performed.
> > > 
> > > 								Honza
> > > 
> > 
> > Sorry I misunderstood your original question.
> > 
> > One reason that you might want to have a "discard" option is to allow a system
> > admin to mount without barriers to protect flaky hardware (we have had some
> > mixed results for example). As you say, the user probably wants to have the
> > ioctl do the discard and should be reasonable for doing it only on solid
> > devices,
> 
> The question is what in does on device other than SSD. I know it does
> not harm the deivce, but is there some kernel logic preventing the trim
> command to be send to device that does not support it ? I hope so.
> 

Yes, there is a check whether device support trim in blkdev_issue_discard
code.

-Lukas

> 
> > 
> > Regards,
> > 
> > Ric
> > 
> 

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