From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40534) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bDPiB-0000Ub-FF for qemu-devel@nongnu.org; Thu, 16 Jun 2016 01:19:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bDPi9-0000F0-Iq for qemu-devel@nongnu.org; Thu, 16 Jun 2016 01:19:26 -0400 Date: Thu, 16 Jun 2016 13:19:13 +0800 From: Fam Zheng Message-ID: <20160616051913.GH12178@ad.usersys.redhat.com> References: <1465939839-30097-1-git-send-email-eblake@redhat.com> <1465939839-30097-7-git-send-email-eblake@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1465939839-30097-7-git-send-email-eblake@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 06/17] iscsi: Advertise realistic limits to block layer List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, kwolf@redhat.com, qemu-block@nongnu.org, Peter Lieven , Max Reitz , Ronnie Sahlberg , Paolo Bonzini On Tue, 06/14 15:30, Eric Blake wrote: > The function sector_limits_lun2qemu() returns a value in units of > the block layer's 512-byte sector, and can be as large as > 0x40000000, which is much larger than the block layer's inherent > limit of BDRV_REQUEST_MAX_SECTORS. The block layer already > handles '0' as a synonym to the inherent limit, and it is nicer > to return this value than it is to calculate an arbitrary > maximum, for two reasons: we want to ensure that the block layer > continues to special-case '0' as 'no limit beyond the inherent > limits'; and we want to be able to someday expand the block > layer to allow 64-bit limits, where auditing for uses of > BDRV_REQUEST_MAX_SECTORS will help us make sure we aren't > artificially constraining iscsi to old block layer limits. > > Signed-off-by: Eric Blake Reviewed-by: Fam Zheng