From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Dilger Subject: Re: [PATCH 0 of 3] [RFC] I/O Hints Date: Thu, 05 Jun 2008 13:19:35 -0600 Message-ID: <20080605191935.GZ2961@webber.adilger.int> References: <20080605104042.GB20308@shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7BIT Cc: "Martin K. Petersen" , linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org To: Jamie Lokier Return-path: In-reply-to: <20080605104042.GB20308@shareable.org> Content-disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Jun 05, 2008 11:40 +0100, Jamie Lokier wrote: > >From a database perspective, I'm thinking it would be very useful to > provide similar information for large files. Database engines have > the same requirement to know stripe width etc., and filesystems > allocate large contiguous extents so it it makes sense to pass the > device characteristics up to the app, with appropriate offset. > > (Same for loopback devices.) > > This is an extreme example of different properties in different offset > ranges - it depends on file allocation. > > Is there scope to extend FIEMAP to pass this sort of information? I have ideas in that direction, but have been gun-shy about presenting them until the existing controversy dies down... I think it is actually fairly straight forward to enhance FIEMAP to allow arbitrary file layouts to be returned to an application. Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.