linux-kernel - Re: [PATCH 1/4] block: Allow drivers to implement BLKDISCARD and add BLKSECDISCARD

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Date:	Fri, 11 Jun 2010 16:52:11 +0900
From:	Kyungmin Park <kmpark@...radead.org>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Adrian Hunter <adrian.hunter@...ia.com>,
	Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] block: Allow drivers to implement BLKDISCARD and add 
	BLKSECDISCARD

On Thu, Jun 10, 2010 at 5:19 PM, Christoph Hellwig <hch@...radead.org> wrote:
> On Fri, Jun 04, 2010 at 12:13:16AM +0300, Adrian Hunter wrote:
>> SD/MMC cards provide an erase operation that is too inefficient to
>> allow file systems to use it, however it is still useful for
>> userspace tools because it is still 10 - 100 times faster than
>> writing zeroes.  Allow the MMC block driver to provide its own
>> BLKDISCARD implementation for this purpose.

I heard if we give trim command without proper align, it writes some
data to align its data.
then user data can be corrupt.
The main problem is we don't know exact used block at filesystem. so
user can corrupt their data easily.

And as you know each manufacturers use their own superpage and align.

>
> That's no good reason.  Almost all current SSD TRIM implementations
> have the same issue, that's why filesustems require the -o discard
> option to enabled it.  In addition I've not actually seen any numbers
> from you on a current kernel.

I hope to see the performance results. In my test, no improvement.

Thank you,
Kyungmin Park

>
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