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Date:	Sat, 23 Apr 2011 09:23:34 -0500
From:	Eric Sandeen <>
To:	Keith Mannthey <>
CC:	Lukas Czerner <>, Tao Ma <>,
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, "
                                clear_opt(sb, DISCARD);

which returns the error message from the calls below it:


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?

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