From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 1/2] bdi: mark the bdi flusher busy when being forked Date: Mon, 11 Apr 2011 14:34:12 -0400 Message-ID: <20110411183412.GC32346@infradead.org> References: <1302157196-1988-1-git-send-email-david@fromorbit.com> <1302157196-1988-2-git-send-email-david@fromorbit.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: xfs@oss.sgi.com, linux-fsdevel@vger.kernel.org To: Dave Chinner Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:36719 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755192Ab1DKSeN (ORCPT ); Mon, 11 Apr 2011 14:34:13 -0400 Content-Disposition: inline In-Reply-To: <1302157196-1988-2-git-send-email-david@fromorbit.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, Apr 07, 2011 at 04:19:55PM +1000, Dave Chinner wrote: > From: Dave Chinner > > Recetn attempts to use writeback_inode_sb_nr_if_idle() in XFs from > memory reclaim context have caused deadlocks because memory reclaim > call be called from a failed allocation during forking a flusher > thread. The shrinker then attempts to trigger writeback and the bdi > is considered idle because writeback is not in progress yet and then > deadlocks because bdi_queue_work() blocks waiting for the > BDI_Pending bit to clear which will never happen because it needs > the fork to complete. > > To avoid this deadlock, consider writeback to be in progress if the > flusher thread is being created. This prevents reclaim from blocking > waiting for it be forked and hence avoids the deadlock. Looks good, Reviewed-by: Christoph Hellwig