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To: Mike Snitzer <snitzer@redhat.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>,
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Subject: Re: [PATCH v5 01/11] block: make generic_make_request handle arbitrarily sized bios
From: "Martin K. Petersen" <martin.petersen@oracle.com>
Organization: Oracle Corporation
References: <yq18u9liwhj.fsf@sermon.lab.mkp.net>
	<1439099990.7880.0.camel@hasee> <20150809064128.GB2436@infradead.org>
	<1439103347.7880.3.camel@hasee> <20150809070128.GA25739@infradead.org>
	<1439104707.7880.8.camel@hasee> <20150810150216.GA22719@redhat.com>
	<yq1si7rgllc.fsf@sermon.lab.mkp.net> <1439230696.26458.6.camel@ssi>
	<yq1bneeh9df.fsf@sermon.lab.mkp.net>
	<20150811024154.GA26351@redhat.com>
Date: Tue, 11 Aug 2015 13:36:39 -0400
In-Reply-To: <20150811024154.GA26351@redhat.com> (Mike Snitzer's message of
	"Mon, 10 Aug 2015 22:41:55 -0400")
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>>>>> "Mike" == Mike Snitzer <snitzer@redhat.com> writes:

Mike> DM-thinp processes discards internally before it passes them down
Mike> (if configured to do so).  If a discard is smaller than the
Mike> granularity of a thinp block (whose size is configurable) or if
Mike> the start and end of the discard's extent is misaligned (relative
Mike> to the thinp blocks mapped to the logical extent) then the discard
Mike> won't actually discard partial thinp blocks.

That's fine. You can throw away anything you don't like as long as
discard_zeroes_data=0.

But I don't understand why having an artificial cap at 2GB fixes
things. Other than making it less likely for you to receive a runt by
virtue of being aligned to a power of two.

-- 
Martin K. Petersen	Oracle Linux Engineering
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