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 from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
