From mboxrd@z Thu Jan 1 00:00:00 1970 From: Blaisorblade Subject: Re: [patch 4/6] mm: merge populate and nopage into fault (fixes nonlinear) Date: Sat, 17 Mar 2007 13:17:00 +0100 References: <20070221023735.6306.83373.sendpatchset@linux.site> <200703130001.13467.blaisorblade@yahoo.it> <20070313011904.GA2746@wotan.suse.de> In-Reply-To: <20070313011904.GA2746@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200703171317.01074.blaisorblade@yahoo.it> Sender: owner-linux-mm@kvack.org Return-Path: To: Nick Piggin Cc: Bill Irwin , Ingo Molnar , Andrew Morton , Linux Memory Management , Linux Kernel , Benjamin Herrenschmidt List-ID: On Tuesday 13 March 2007 02:19, Nick Piggin wrote: > On Tue, Mar 13, 2007 at 12:01:13AM +0100, Blaisorblade wrote: > > On Wednesday 07 March 2007 11:02, Nick Piggin wrote: > > > > Yeah, tmpfs/shm segs are what I was thinking about. If UML can live > > > > with that as well, then I think it might be a good option. > > > > > > Oh, hmm.... if you can truncate these things then you still need to > > > force unmap so you still need i_mmap_nonlinear. > > > > Well, we don't need truncate(), but MADV_REMOVE for memory hotunplug, > > which is way similar I guess. > > > > About the restriction to tmpfs, I have just discovered > > '[PATCH] mm: tracking shared dirty pages' (commit > > d08b3851da41d0ee60851f2c75b118e1f7a5fc89), which already partially > > conflicts with remap_file_pages for file-based mmaps (and that's fully > > fine, for now). > > > > Even if UML does not need it, till now if there is a VMA protection and a > > page hasn't been remapped with remap_file_pages, the VMA protection is > > used (just because it makes sense). > > > > However, it is only used when the PTE is first created - we can never > > change protections on a VMA - so it vma_wants_writenotify() is true (on > > all file-based and on no shmfs based mapping, right?), and we > > write-protect the VMA, it will always be write-protected. > > Yes, I believe that is the case, however I wonder if that is going to be > a problem for you to distinguish between write faults for clean writable > ptes, and write faults for readonly ptes? I wouldn't be able to distinguish them, but am I going to get write faults for clean ptes when vma_wants_writenotify() is false (as seems to be for tmpfs)? I guess not. For tmpfs pages, clean writable PTEs are mapped as writable so they won't give any problem, since vma_wants_writenotify() is false for tmpfs. Correct? > > Also, I'm curious. Since my patches are already changing > > remap_file_pages() code, should they be absolutely merged after yours? > > Is there a big clash? I don't think I did a great deal to fremap.c (mainly > just removing stuff)... Hopefully, we just both modify sys_remap_file_pages(), I'll see soon. -- Inform me of my mistakes, so I can add them to my list! Paolo Giarrusso, aka Blaisorblade http://www.user-mode-linux.org/~blaisorblade Chiacchiera con i tuoi amici in tempo reale! http://it.yahoo.com/mail_it/foot/*http://it.messenger.yahoo.com -- 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