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From: "Martin K. Petersen" <mkp@mkp.net>
To: Christoph Hellwig <hch@infradead.org>
Cc: Dmitry Monakhov <dmonakhov@openvz.org>,
	linux-kernel@vger.kernel.org, jens.axboe@oracle.com
Subject: Re: [PATCH 1/4] block: implement compatible DISCARD support
Date: Thu, 11 Feb 2010 09:40:05 -0500	[thread overview]
Message-ID: <yq1eikrzvi2.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <20100211122154.GA12417@infradead.org> (Christoph Hellwig's message of "Thu, 11 Feb 2010 07:21:54 -0500")

>>>>> "Christoph" == Christoph Hellwig <hch@infradead.org> writes:
>> 5) It use allocated_page instead of ZERO_PAGE.

Christoph> That's incorrect - both the scsi WRITE SAME and ATA UNMAP
Christoph> implementations write to the payload.  I have some plans to
Christoph> change that an get rid of the payload entirely, but I need to
Christoph> get back to the discard work and look at it in more detail.

I've been away for a couple of weeks (got back yesterday).  Just a heads
up that I've been working on block layer support for WRITE SAME as well
as a discard revamp the last little while.  I'll try to post those
patches today or tomorrow.

Just to give you an idea: I distinguish between discarding, clearing,
and filling a block range.

blkdev_issue_clear() is used for explicitly zeroing a region.  If the
target supports RZAT/TPRZ, discard will be used instead of zero filling.

blkdev_issue_discard() is for trimming without caring about what's left
in the blocks.  And blkdev_issue_fill() can be used to do a write same
pass on a range (for bulk initializing RAID blocks, for instance).

-- 
Martin K. Petersen	Oracle Linux Engineering


      parent reply	other threads:[~2010-02-11 15:10 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-02-11 10:53 Dmitry Monakhov
2010-02-11 10:57 ` [PATCH 2/4] block: support compat discard mode by default Dmitry Monakhov
2010-02-11 11:25   ` Dmitry Monakhov
2010-02-11 12:22   ` Christoph Hellwig
2010-02-11 10:59 ` [PATCH 3/4] ext4: convert extent zeroout to generic function Dmitry Monakhov
2010-02-11 10:59   ` Dmitry Monakhov
2010-02-11 11:01 ` [PATCH 4/4] btrfs: add discard_compat support Dmitry Monakhov
2010-02-11 11:15   ` Dmitry Monakhov
2010-02-11 12:21 ` [PATCH 1/4] block: implement compatible DISCARD support Christoph Hellwig
2010-02-11 12:59   ` Dmitry Monakhov
2010-02-11 13:09     ` Christoph Hellwig
2010-02-11 13:45       ` Dmitry Monakhov
2010-02-11 14:06         ` Christoph Hellwig
2010-02-11 14:40   ` Martin K. Petersen [this message]

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