From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Mason Subject: Re: [rfc][patch 2/2] buffer, btrfs: fix page_mkwrite error cases Date: Tue, 03 Mar 2009 09:47:52 -0500 Message-ID: <1236091672.782.7.camel@think.oraclecorp.com> References: <20090303103838.GC17042@wotan.suse.de> <20090303104114.GD17042@wotan.suse.de> <1236090363.782.6.camel@think.oraclecorp.com> <20090303144146.GA18142@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Linux Memory Management List , linux-fsdevel@vger.kernel.org To: Nick Piggin Return-path: In-Reply-To: <20090303144146.GA18142@wotan.suse.de> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Tue, 2009-03-03 at 15:41 +0100, Nick Piggin wrote: > On Tue, Mar 03, 2009 at 09:26:03AM -0500, Chris Mason wrote: > > On Tue, 2009-03-03 at 11:41 +0100, Nick Piggin wrote: > > > page_mkwrite is called with neither the page lock nor the ptl held. This > > > means a page can be concurrently truncated or invalidated out from underneath > > > it. Callers are supposed to prevent truncate races themselves, however > > > previously the only thing they can do in case they hit one is to raise a > > > SIGBUS. A sigbus is wrong for the case that the page has been invalidated > > > or truncated within i_size (eg. hole punched). Callers may also have to > > > perform memory allocations in this path, where again, SIGBUS would be wrong. > > > > > > The previous patch made it possible to properly specify errors. Convert > > > the generic buffer.c code and btrfs to return sane error values > > > (in the case of page removed from pagecache, VM_FAULT_NOPAGE will cause the > > > fault handler to exit without doing anything, and the fault will be retried > > > properly). > > > > > > > Thanks Nick. I think the btrfs patch needs an extra } to compile, but > > it looks fine. > > OK... btrfs is obviously untested :) I just got to btrfs and realised > that probably most of the non-trivial ones will want fs maintainers to > take a look. I *think* the following errors should mostly be right: > > !page->mapping ==> VM_FAULT_NOPAGE (just cause the VM to retry the fault) > -ENOMEM ==> VM_FAULT_OOM > any other error ==> VM_FAULT_SIGBUS > It's no problem, the patch made things more clear than it was before. You can add an sob for me once it compiles ;) -chris -- 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