From: Andrew Morton Subject: Re: [patch] fs: fix deadlocks in writeback_if_idle Date: Thu, 25 Nov 2010 12:30:01 -0800 Message-ID: <20101125123001.9bc75815.akpm@linux-foundation.org> References: <20101123100239.GA4232@amd> <1290515274-sup-3895@think> <20101124144740.bffb2716.akpm@linux-foundation.org> <4CEE2F5E.4070608@panasas.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Chris Mason , Nick Piggin , linux-fsdevel , Al Viro , linux-ext4 , linux-btrfs , Jan Kara , Eric Sandeen , "Theodore Ts'o" To: Boaz Harrosh Return-path: In-Reply-To: <4CEE2F5E.4070608@panasas.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Thu, 25 Nov 2010 11:41:50 +0200 Boaz Harrosh wrote: > On 11/25/2010 12:47 AM, Andrew Morton wrote: > > On Tue, 23 Nov 2010 07:34:07 -0500 > > Chris Mason wrote: > > > >> For btrfs there's only one bdi per SB, but for most everyone else a disk > >> with a bunch of partitions is going to have multiple filesystems on the > >> same bdi. > > > > um, please explain why that wasn't idiotic? The BDI is a > > representation of a backing device and it's *supposed* to provide > > visibility into what's happening against other partitions on the same > > device. Creating a BDI per SB (it didn't even occur to me to think > > that a filesystem was even able to do this) breaks that. > > > > In btrfs an SB my span multiple partitions. How else can it be solved? Associate a number of bdi's with the superblock. If necessary, convert core kernel to operate on groups of BDI's. Which shouldn't be too hard given that core kernel already does this, for MD. ie: something which faithfully models what is actually going on, rather than simply bending reality.