From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 9 Oct 2006 22:29:05 -0700 From: Andrew Morton Subject: Re: [patch] mm: bug in set_page_dirty_buffers Message-Id: <20061009222905.ddd270a6.akpm@osdl.org> In-Reply-To: <20061010052248.GB24600@wotan.suse.de> References: <20061009202039.b6948a93.akpm@osdl.org> <20061010033412.GH15822@wotan.suse.de> <20061009205030.e247482e.akpm@osdl.org> <20061010035851.GK15822@wotan.suse.de> <20061009211404.ad112128.akpm@osdl.org> <20061010042144.GM15822@wotan.suse.de> <20061009213806.b158ea82.akpm@osdl.org> <20061010044745.GA24600@wotan.suse.de> <20061009220127.c4721d2d.akpm@osdl.org> <20061010052248.GB24600@wotan.suse.de> 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 Cc: Linus Torvalds , Peter Zijlstra , Linux Memory Management List , Greg KH List-ID: On Tue, 10 Oct 2006 07:22:48 +0200 Nick Piggin wrote: > On Mon, Oct 09, 2006 at 10:01:27PM -0700, Andrew Morton wrote: > > On Tue, 10 Oct 2006 06:47:45 +0200 > > Nick Piggin wrote: > > > > There we can trylock all the pages and bale if any fail. > > > > > > Hmm, try_to_unmap is OK because the page is already locked. page_remove_rmap > > > isn't allowed to fail. > > > > I was talking about try_to_unmap_cluster(). > > But page_remove_rmap's many callers are still screwed. Take do_wp_page, > for example. > > > > > But where? locking the page is the preferred way to solve this stuff. > > > > (Well, locking the buffers might work, but isn't needed, and locking the > > > > page covers other stuff) > > > > > > AFAIKS, it is just fs/buffer.c that is racy. > > > > Need to review all ->set_page_dirty, ->writepage, ->invalidatepage, ->etc > > implementations before we can say that. ^^^ this > > > Why can't it use > > > mapping->private_lock or the buffer bit spinlock? > > > > block_invalidatepage() wants to do lock_buffer(). > > > > It can probably be made to work. But a sane interface is "when dinking > > with page internals, lock the page". > > I disagree because it will lead to horrible hacks because many callers > can't sleep. If anything I would much prefer an innermost-spinlock in > page->flags that specifically excludes truncate. Actually tree_lock can > do that now, provided we pin mapping in all callers to set_page_dirty > (which we should do). > > Then the locking protocol is up to fs/buffer.c. You could set a bit in > the buffer "BH_Invalidated" in truncate before clearing dirty, and test > for that bit in set_page_dirty_buffers? -- 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