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To: Ming Lin <mlin@kernel.org>
From: "Martin K. Petersen" <martin.petersen@oracle.com>
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Date: Mon, 10 Aug 2015 22:00:44 -0400
In-Reply-To: <1439230696.26458.6.camel@ssi> (Ming Lin's message of "Mon, 10
	Aug 2015 11:18:16 -0700")
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Cc: Mike Snitzer <snitzer@redhat.com>, Ming Lei <ming.lei@canonical.com>,
	device-mapper development <dm-devel@redhat.com>,
	Christoph Hellwig <hch@lst.de>, Alasdair Kergon <agk@redhat.com>,
	Lars Ellenberg <drbd-dev@lists.linbit.com>,
	Philip Kelleher <pjk1939@linux.vnet.ibm.com>,
	Christoph Hellwig <hch@infradead.org>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Nitin Gupta <ngupta@vflare.org>, Ming Lin <ming.l@ssi.samsung.com>,
	Oleg Drokin <oleg.drokin@intel.com>,
	Al Viro <viro@zeniv.linux.org.uk>, Jens Axboe <axboe@kernel.dk>,
	axboe@fb.com, Andreas Dilger <andreas.dilger@intel.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Geoff Levand <geoff@infradead.org>, Jiri Kosina <jkosina@suse.cz>,
	lkml <linux-kernel@vger.kernel.org>, Jim Paris <jim@jtan.com>,
	Minchan Kim <minchan@kernel.org>, Joe Thornber <ejt@redhat.com>,
	Dongsu Park <dpark@posteo.net>, drbd-user@lists.linbit.com
Subject: Re: [Drbd-dev] [PATCH v5 01/11] block: make generic_make_request
	handle arbitrarily sized bios
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>>>>> "Ming" == Ming Lin <mlin@kernel.org> writes:

Ming> Did you mean still use (UINT_MAX >> 9) in blkdev_issue_discard()?

Ming> But that doesn't work for dm-thinp. See Kent's suggestion to use
Ming> 1<<31.

I'm not sure why things are not working for dm-thinp. Presumably Kent's
code would split the discard at a granularity boundary so why would that
cause problems for dm?

In looking at this I just found out that we'll corrupt data on certain
SCSI configs with the granularity enforcement in place. I'll have to
conjure up a fix for that...

-- 
Martin K. Petersen	Oracle Linux Engineering