From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Tue, 30 Jan 2007 15:21:19 -0800 From: Andrew Morton Subject: Re: [patch 0/9] buffered write deadlock fix Message-Id: <20070130152119.e0a18e58.akpm@osdl.org> In-Reply-To: <20070130125558.ae9119b0.akpm@osdl.org> References: <20070129081905.23584.97878.sendpatchset@linux.site> <20070130125558.ae9119b0.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin , Hugh Dickins , Linux Kernel , Linux Filesystems , Linux Memory Management List-ID: On Tue, 30 Jan 2007 12:55:58 -0800 Andrew Morton wrote: > y'know, four or five years back I fixed this bug by doing > > current->locked_page = page; > > in the write() code, and then teaching the pagefault code to avoid locking > the same page. Patch below. > > But then evil mean Hugh pointed out that the patch is still vulnerable to > ab/ba deadlocking so I dropped it. And he was right, of course. Task A holds file a's i_mutex and takes a fault against file b's page. Task B holds file b's i_mutex and takes a fault against file a's page. Drat. I wonder if there's a sane way of preventing that. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org