On Thu, 14 Feb 2008 22:49:04 -0800 Christoph Lameter <[EMAIL PROTECTED]> wrote:
> These special additional callbacks are required because XPmem (and likely > other mechanisms) do use their own rmap (multiple processes on a series > of remote Linux instances may be accessing the memory of a process). > F.e. XPmem may have to send out notifications to remote Linux instances > and receive confirmation before a page can be freed. > > So we handle this like an additional Linux reverse map that is walked after > the existing rmaps have been walked. We leave the walking to the driver that > is then able to use something else than a spinlock to walk its reverse > maps. So we can actually call the driver without holding spinlocks while > we hold the Pagelock. > > However, we cannot determine the mm_struct that a page belongs to at > that point. The mm_struct can only be determined from the rmaps by the > device driver. > > We add another pageflag (PageExternalRmap) that is set if a page has > been remotely mapped (f.e. by a process from another Linux instance). > We can then only perform the callbacks for pages that are actually in > remote use. > > Rmap notifiers need an extra page bit and are only available > on 64 bit platforms. This functionality is not available on 32 bit! > > A notifier that uses the reverse maps callbacks does not need to provide > the invalidate_page() method that is called when locks are held. > hrm. > +#define mmu_rmap_notifier(function, args...) \ > + do { \ > + struct mmu_rmap_notifier *__mrn; \ > + struct hlist_node *__n; \ > + \ > + rcu_read_lock(); \ > + hlist_for_each_entry_rcu(__mrn, __n, \ > + &mmu_rmap_notifier_list, hlist) \ > + if (__mrn->ops->function) \ > + __mrn->ops->function(__mrn, args); \ > + rcu_read_unlock(); \ > + } while (0); > + buggy macro: use locals. > +#define mmu_rmap_notifier(function, args...) \ > + do { \ > + if (0) { \ > + struct mmu_rmap_notifier *__mrn; \ > + \ > + __mrn = (struct mmu_rmap_notifier *)(0x00ff); \ > + __mrn->ops->function(__mrn, args); \ > + } \ > + } while (0); > + Same observation as in the other patch. > =================================================================== > --- linux-2.6.orig/mm/mmu_notifier.c 2008-02-14 21:17:51.000000000 -0800 > +++ linux-2.6/mm/mmu_notifier.c 2008-02-14 21:21:04.000000000 -0800 > @@ -74,3 +74,37 @@ void mmu_notifier_unregister(struct mmu_ > } > EXPORT_SYMBOL_GPL(mmu_notifier_unregister); > > +#ifdef CONFIG_64BIT > +static DEFINE_SPINLOCK(mmu_notifier_list_lock); > +HLIST_HEAD(mmu_rmap_notifier_list); > + > +void mmu_rmap_notifier_register(struct mmu_rmap_notifier *mrn) > +{ > + spin_lock(&mmu_notifier_list_lock); > + hlist_add_head_rcu(&mrn->hlist, &mmu_rmap_notifier_list); > + spin_unlock(&mmu_notifier_list_lock); > +} > +EXPORT_SYMBOL(mmu_rmap_notifier_register); > + > +void mmu_rmap_notifier_unregister(struct mmu_rmap_notifier *mrn) > +{ > + spin_lock(&mmu_notifier_list_lock); > + hlist_del_rcu(&mrn->hlist); > + spin_unlock(&mmu_notifier_list_lock); > +} > +EXPORT_SYMBOL(mmu_rmap_notifier_unregister); > > +/* > + * Export a page. > + * > + * Pagelock must be held. > + * Must be called before a page is put on an external rmap. > + */ > +void mmu_rmap_export_page(struct page *page) > +{ > + BUG_ON(!PageLocked(page)); > + SetPageExternalRmap(page); > +} > +EXPORT_SYMBOL(mmu_rmap_export_page); The other patch used EXPORT_SYMBOL_GPL. -- 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/