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Date: Sat, 8 Aug 2015 23:41:28 -0700
From: Christoph Hellwig <hch@infradead.org>
To: Ming Lin <mlin@kernel.org>
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Cc: Mike Snitzer <snitzer@redhat.com>, Ming Lei <ming.lei@canonical.com>,
	device-mapper development <dm-devel@redhat.com>,
	Joshua Morris <josh.h.morris@us.ibm.com>, Alasdair Kergon <agk@redhat.com>,
	Lars Ellenberg <drbd-dev@lists.linbit.com>,
	Philip Kelleher <pjk1939@linux.vnet.ibm.com>,
	Christoph Hellwig <hch@lst.de>, 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>,
	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>, Dongsu Park <dpark@posteo.net>,
	drbd-user@lists.linbit.com
Subject: Re: [Drbd-dev] [dm-devel] [PATCH v5 01/11] block: make
 generic_make_request handle arbitrarily sized bios
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On Sat, Aug 08, 2015 at 10:59:50PM -0700, Ming Lin wrote:
> +/*
> + * Ensure that max discard sectors doesn't overflow bi_size and hopefully
> + * it is of the proper granularity as long as the granularity is a power
> + * of two.
> + */
> +#define MAX_DISCARD_SECTORS ((1U << 31) >> 9)

Thisn't isn't MAX_DISCARD_SECTORS, it's MAX_BIO_SECTORS.  If we ever
to something like Kent's multipage biovecs we'll actually need it for
regular read/write bios in addition to discard and write same.

Except for that the patch looks reasonable to me.