linux-ext4 - Re: Quick EXT4 discard question

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Date:	Sat, 23 Apr 2011 09:23:34 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Keith Mannthey <kmannth@...ibm.com>
CC:	Lukas Czerner <lczerner@...hat.com>, Tao Ma <tm@....ma>,
	linux-ext4@...r.kernel.org
Subject: Re: Quick EXT4 discard question

On 4/22/11 11:08 AM, Keith Mannthey wrote:
> On Fri, 2011-04-22 at 09:44 +0200, Lukas Czerner wrote:

...

>> Actually you can query that with hdparm -I /path/to/the/device and you
>> should see something like
>>
>> *   Data Set Management TRIM supported
>>
>> in the output.
> 
> I see 
> 
> *	Data Set Management TRIM supported
> ...
> *	Deterministic read after TRIM
> 
> set on my devices. 
> 
> Thanks,
>   Keith 

So the way you get your message is:

                        ret = ext4_issue_discard(sb, entry->group,
                                        entry->start_blk, entry->count);
                        if (unlikely(ret == -EOPNOTSUPP)) {
                                ext4_warning(sb, "discard not supported, "
                                                 "disabling");
                                clear_opt(sb, DISCARD);
                        }

which returns the error message from the calls below it:

ext4_issue_discard
	sb_issue_discard
		blkdev_issue_discard

and EOPNOTSUPP is pretty clear... I wonder if it could be that a discard request
on a particular boundary is causing it to be rejected?

-Eric
		
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