From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [patch 8/8] fs: add i_op->sync_inode Date: Fri, 7 Jan 2011 02:29:34 -0500 Message-ID: <20110107072934.GA2849@infradead.org> References: <20101218015117.759480620@kernel.dk> <20101229151246.GA22033@infradead.org> <20110104062725.GD3402@amd> <20110104065736.GA8013@infradead.org> <20110104080323.GC4090@amd> <20110104092501.GB2760@infradead.org> <20110104094922.GA4812@amd> <20110106204510.GA2872@infradead.org> <20110107044734.GA4552@amd> <20110107072430.GA32308@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton To: Nick Piggin Return-path: Content-Disposition: inline In-Reply-To: <20110107072430.GA32308@infradead.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Fri, Jan 07, 2011 at 02:24:30AM -0500, Christoph Hellwig wrote: > On Fri, Jan 07, 2011 at 03:47:34PM +1100, Nick Piggin wrote: > > No, you misunderstand 1. I am saying they should be treated as > > WB_SYNC_NONE. > > > > In fact 2 would cause much more IO, because dirty writeout would > > never clean them so it will just keep writing them out. I don't > > know how 2 could be feasible. > > WB_SYNC_NONE means ->write_inode behaves non-blocking. That is > we do not block on memory allocations, and we do not take locks > blocking. Most journaling filesystems currently take the easy > way out an make it a no-op due to that, but take a look at XFS > how complicated it is to avoid the blocking if you want a non-noop > implementation. Btw, there's an easy way how we could get this right, in fact the write_inode in XFS is already trying to do it, it's just the caller not copying with it: - if we can't get locks for a non-blocking ->write_inode we return EAGAIN, and the callers sets the dirty bits again.