From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 11 Jan 2001 10:43:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 11 Jan 2001 10:43:35 -0500 Received: from roc-24-95-203-215.rochester.rr.com ([24.95.203.215]:44038 "EHLO d185fcbd7.rochester.rr.com") by vger.kernel.org with ESMTP id ; Thu, 11 Jan 2001 10:43:25 -0500 Date: Thu, 11 Jan 2001 10:43:04 -0500 From: Chris Mason To: Marcelo Tosatti cc: linux-kernel@vger.kernel.org Subject: Re: Possible deadlock with ->writepaged version of flush_dirty_buffers() and 2.4.0 Message-ID: <517420000.979227784@tiny> In-Reply-To: X-Mailer: Mulberry/2.0.6b1 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, January 10, 2001 05:56:09 PM -0200 Marcelo Tosatti wrote: > > Hi Chris, > > It seems there is a possible deadlock condition with your patch which > changes flush_dirty_buffers() to use ->writepage (something which we > _definately_ want for 2.5). Take a look: > Yes, good catch. > > mark_buffer_dirty->balance_dirty->wakeup_bdflush->flush_dirty_buffers-> > writepage->block_write_full_page->__block_write_full_page->get_block-> > ext2_get_block->ext2_alloc_branch-> > > ext2_alloc_block->ext2_new_block->lock_super > or > getblk()->lock_super > > > I dont see any reason why this deadlock could'nt happen in practice now. > It won't happen until someone other than fs/buffer.c starts marking ext2 pages dirty. The normal file write path will make sure that any dirty buffers are mapped, so the ext2_get_block code is never run. > If I'm right, it will pretty nasty to fix this. One possible solution is > to _never_ call mark_buffer_dirty() with the superblock lock held (ext2 > has a lot of places likes this right now) > This is probably the best solution, since it is a good idea regardless of my patch. -chris - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/