From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Dike Subject: Re: [RFC][PATCH] ChunkFS: fs fission for faster fsck Date: Thu, 26 Apr 2007 12:05:04 -0400 Message-ID: <20070426160504.GA7970@c2.user-mode-linux.org> References: <17965.60841.900376.524639@gargle.gargle.HOWL> <17966.23512.363955.141489@gargle.gargle.HOWL> <17967.15531.450627.972572@gargle.gargle.HOWL> <20070425224710.GB16129@nifty> <20070426141455.GA6155@c2.user-mode-linux.org> <4630CAEC.2050909@ksu.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Valerie Henson , Nikita Danilov , David Lang , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, riel@surriel.com, zab@zabbo.net, arjan@infradead.org, suparna@in.ibm.com, brandon@ifup.org, karunasagark@gmail.com To: Amit Gud Return-path: Content-Disposition: inline In-Reply-To: <4630CAEC.2050909@ksu.edu> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Thu, Apr 26, 2007 at 10:53:16AM -0500, Amit Gud wrote: > Jeff Dike wrote: > >How about this case: > > > > Growing file starts in chunk A. > > Overflows into chunk B. > > Delete file in chunk A. > > Growing file overflows chunk B and spots new free space in > >chunk A (and nothing anywhere else) > > Overflows into chunk A > > Delete file in chunk B. > > Overflow into chunk B again. > > > >Maybe this is not realistic, but in the absence of a mechanism to pull > >data back from an overflow chunk, it seems at least a theoretical > >possibility that there could be > 1 continuation inodes per file per > >chunk. > > > > Preventive measures are taken to limit only one continuation inode per > file per chunk. This can be done easily in the chunk allocation > algorithm for disk space. Although I'm not quite sure what you mean by > "Delete file in chunk A". If you are referring to same file thats > growing, then deletion is not possible, because individual parts of any > file in any chunk cannot be deleted. No, I'm referring to a different file. The scenario is that you have a growing file in a nearly full disk with files being deleted (and thus space being freed) such that allocations for the growing file bounce back and forth between chunks. Jeff -- Work email - jdike at linux dot intel dot com