Merge tag 'for-linus-5.5b-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull more xen updates from Juergen Gross:

 - a patch to fix a build warning

 - a cleanup of no longer needed code in the Xen event handling

 - a small series for the Xen grant driver avoiding high order
   allocations and replacing an insane global limit by a per-call one

 - a small series fixing Xen frontend/backend module referencing

* tag 'for-linus-5.5b-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen-blkback: allow module to be cleanly unloaded
  xen/xenbus: reference count registered modules
  xen/gntdev: switch from kcalloc() to kvcalloc()
  xen/gntdev: replace global limit of mapped pages by limit per call
  xen/gntdev: remove redundant non-zero check on ret
  xen/events: remove event handling recursion detection

5 files changed, 44 insertions, 62 deletions

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 6c8843968a52..499eff7d3f65 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -1213,31 +1213,21 @@ void xen_send_IPI_one(unsigned int cpu, enum ipi_vector vector)
 	notify_remote_via_irq(irq);
 }
 
-static DEFINE_PER_CPU(unsigned, xed_nesting_count);
-
 static void __xen_evtchn_do_upcall(void)
 {
 	struct vcpu_info *vcpu_info = __this_cpu_read(xen_vcpu);
-	int cpu = get_cpu();
-	unsigned count;
+	int cpu = smp_processor_id();
 
 	do {
 		vcpu_info->evtchn_upcall_pending = 0;
 
-		if (__this_cpu_inc_return(xed_nesting_count) - 1)
-			goto out;
-
 		xen_evtchn_handle_events(cpu);
 
 		BUG_ON(!irqs_disabled());
 
-		count = __this_cpu_read(xed_nesting_count);
-		__this_cpu_write(xed_nesting_count, 0);
-	} while (count != 1 || vcpu_info->evtchn_upcall_pending);
-
-out:
+		virt_rmb(); /* Hypervisor can set upcall pending. */
 
-	put_cpu();
+	} while (vcpu_info->evtchn_upcall_pending);
 }
 
 void xen_evtchn_do_upcall(struct pt_regs *regs)
diff --git a/drivers/xen/gntdev-common.h b/drivers/xen/gntdev-common.h
index 91e44c04f787..9a3960ecff6c 100644
--- a/drivers/xen/gntdev-common.h
+++ b/drivers/xen/gntdev-common.h
@@ -81,7 +81,7 @@ void gntdev_add_map(struct gntdev_priv *priv, struct gntdev_grant_map *add);
 
 void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map);
 
-bool gntdev_account_mapped_pages(int count);
+bool gntdev_test_page_count(unsigned int count);
 
 int gntdev_map_grant_pages(struct gntdev_grant_map *map);
 
diff --git a/drivers/xen/gntdev-dmabuf.c b/drivers/xen/gntdev-dmabuf.c
index 2c4f324f8626..63f0857bf62d 100644
--- a/drivers/xen/gntdev-dmabuf.c
+++ b/drivers/xen/gntdev-dmabuf.c
@@ -446,7 +446,7 @@ dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags,
 {
 	struct gntdev_grant_map *map;
 
-	if (unlikely(count <= 0))
+	if (unlikely(gntdev_test_page_count(count)))
 		return ERR_PTR(-EINVAL);
 
 	if ((dmabuf_flags & GNTDEV_DMA_FLAG_WC) &&
@@ -459,11 +459,6 @@ dmabuf_exp_alloc_backing_storage(struct gntdev_priv *priv, int dmabuf_flags,
 	if (!map)
 		return ERR_PTR(-ENOMEM);
 
-	if (unlikely(gntdev_account_mapped_pages(count))) {
-		pr_debug("can't map %d pages: over limit\n", count);
-		gntdev_put_map(NULL, map);
-		return ERR_PTR(-ENOMEM);
-	}
 	return map;
 }
 
@@ -771,7 +766,7 @@ long gntdev_ioctl_dmabuf_exp_from_refs(struct gntdev_priv *priv, int use_ptemod,
 	if (copy_from_user(&op, u, sizeof(op)) != 0)
 		return -EFAULT;
 
-	if (unlikely(op.count <= 0))
+	if (unlikely(gntdev_test_page_count(op.count)))
 		return -EINVAL;
 
 	refs = kcalloc(op.count, sizeof(*refs), GFP_KERNEL);
@@ -818,7 +813,7 @@ long gntdev_ioctl_dmabuf_imp_to_refs(struct gntdev_priv *priv,
 	if (copy_from_user(&op, u, sizeof(op)) != 0)
 		return -EFAULT;
 
-	if (unlikely(op.count <= 0))
+	if (unlikely(gntdev_test_page_count(op.count)))
 		return -EINVAL;
 
 	gntdev_dmabuf = dmabuf_imp_to_refs(priv->dmabuf_priv,
diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index a04ddf2a68af..4fc83e3f5ad3 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -55,12 +55,10 @@ MODULE_AUTHOR("Derek G. Murray <Derek.Murray@cl.cam.ac.uk>, "
 	      "Gerd Hoffmann <kraxel@redhat.com>");
 MODULE_DESCRIPTION("User-space granted page access driver");
 
-static int limit = 1024*1024;
-module_param(limit, int, 0644);
-MODULE_PARM_DESC(limit, "Maximum number of grants that may be mapped by "
-		"the gntdev device");
-
-static atomic_t pages_mapped = ATOMIC_INIT(0);
+static unsigned int limit = 64*1024;
+module_param(limit, uint, 0644);
+MODULE_PARM_DESC(limit,
+	"Maximum number of grants that may be mapped by one mapping request");
 
 static int use_ptemod;
 
@@ -71,9 +69,9 @@ static struct miscdevice gntdev_miscdev;
 
 /* ------------------------------------------------------------------ */
 
-bool gntdev_account_mapped_pages(int count)
+bool gntdev_test_page_count(unsigned int count)
 {
-	return atomic_add_return(count, &pages_mapped) > limit;
+	return !count || count > limit;
 }
 
 static void gntdev_print_maps(struct gntdev_priv *priv,
@@ -114,14 +112,14 @@ static void gntdev_free_map(struct gntdev_grant_map *map)
 		gnttab_free_pages(map->count, map->pages);
 
 #ifdef CONFIG_XEN_GRANT_DMA_ALLOC
-	kfree(map->frames);
+	kvfree(map->frames);
 #endif
-	kfree(map->pages);
-	kfree(map->grants);
-	kfree(map->map_ops);
-	kfree(map->unmap_ops);
-	kfree(map->kmap_ops);
-	kfree(map->kunmap_ops);
+	kvfree(map->pages);
+	kvfree(map->grants);
+	kvfree(map->map_ops);
+	kvfree(map->unmap_ops);
+	kvfree(map->kmap_ops);
+	kvfree(map->kunmap_ops);
 	kfree(map);
 }
 
@@ -135,12 +133,13 @@ struct gntdev_grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count,
 	if (NULL == add)
 		return NULL;
 
-	add->grants    = kcalloc(count, sizeof(add->grants[0]), GFP_KERNEL);
-	add->map_ops   = kcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
-	add->unmap_ops = kcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
-	add->kmap_ops  = kcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
-	add->kunmap_ops = kcalloc(count, sizeof(add->kunmap_ops[0]), GFP_KERNEL);
-	add->pages     = kcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
+	add->grants    = kvcalloc(count, sizeof(add->grants[0]), GFP_KERNEL);
+	add->map_ops   = kvcalloc(count, sizeof(add->map_ops[0]), GFP_KERNEL);
+	add->unmap_ops = kvcalloc(count, sizeof(add->unmap_ops[0]), GFP_KERNEL);
+	add->kmap_ops  = kvcalloc(count, sizeof(add->kmap_ops[0]), GFP_KERNEL);
+	add->kunmap_ops = kvcalloc(count,
+				   sizeof(add->kunmap_ops[0]), GFP_KERNEL);
+	add->pages     = kvcalloc(count, sizeof(add->pages[0]), GFP_KERNEL);
 	if (NULL == add->grants    ||
 	    NULL == add->map_ops   ||
 	    NULL == add->unmap_ops ||
@@ -159,8 +158,8 @@ struct gntdev_grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count,
 	if (dma_flags & (GNTDEV_DMA_FLAG_WC | GNTDEV_DMA_FLAG_COHERENT)) {
 		struct gnttab_dma_alloc_args args;
 
-		add->frames = kcalloc(count, sizeof(add->frames[0]),
-				      GFP_KERNEL);
+		add->frames = kvcalloc(count, sizeof(add->frames[0]),
+				       GFP_KERNEL);
 		if (!add->frames)
 			goto err;
 
@@ -241,8 +240,6 @@ void gntdev_put_map(struct gntdev_priv *priv, struct gntdev_grant_map *map)
 	if (!refcount_dec_and_test(&map->users))
 		return;
 
-	atomic_sub(map->count, &pages_mapped);
-
 	if (map->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
 		notify_remote_via_evtchn(map->notify.event);
 		evtchn_put(map->notify.event);
@@ -506,7 +503,6 @@ static const struct mmu_interval_notifier_ops gntdev_mmu_ops = {
 static int gntdev_open(struct inode *inode, struct file *flip)
 {
 	struct gntdev_priv *priv;
-	int ret = 0;
 
 	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 	if (!priv)
@@ -518,16 +514,12 @@ static int gntdev_open(struct inode *inode, struct file *flip)
 #ifdef CONFIG_XEN_GNTDEV_DMABUF
 	priv->dmabuf_priv = gntdev_dmabuf_init(flip);
 	if (IS_ERR(priv->dmabuf_priv)) {
-		ret = PTR_ERR(priv->dmabuf_priv);
-		kfree(priv);
-		return ret;
-	}
-#endif
+		int ret = PTR_ERR(priv->dmabuf_priv);
 
-	if (ret) {
 		kfree(priv);
 		return ret;
 	}
+#endif
 
 	flip->private_data = priv;
 #ifdef CONFIG_XEN_GRANT_DMA_ALLOC
@@ -573,7 +565,7 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
 	if (copy_from_user(&op, u, sizeof(op)) != 0)
 		return -EFAULT;
 	pr_debug("priv %p, add %d\n", priv, op.count);
-	if (unlikely(op.count <= 0))
+	if (unlikely(gntdev_test_page_count(op.count)))
 		return -EINVAL;
 
 	err = -ENOMEM;
@@ -581,12 +573,6 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv,
 	if (!map)
 		return err;
 
-	if (unlikely(gntdev_account_mapped_pages(op.count))) {
-		pr_debug("can't map: over limit\n");
-		gntdev_put_map(NULL, map);
-		return err;
-	}
-
 	if (copy_from_user(map->grants, &u->refs,
 			   sizeof(map->grants[0]) * op.count) != 0) {
 		gntdev_put_map(NULL, map);
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index 5b471889d723..c21be6e9d38a 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -232,9 +232,16 @@ int xenbus_dev_probe(struct device *_dev)
 		return err;
 	}
 
+	if (!try_module_get(drv->driver.owner)) {
+		dev_warn(&dev->dev, "failed to acquire module reference on '%s'\n",
+			 drv->driver.name);
+		err = -ESRCH;
+		goto fail;
+	}
+
 	err = drv->probe(dev, id);
 	if (err)
-		goto fail;
+		goto fail_put;
 
 	err = watch_otherend(dev);
 	if (err) {
@@ -244,6 +251,8 @@ int xenbus_dev_probe(struct device *_dev)
 	}
 
 	return 0;
+fail_put:
+	module_put(drv->driver.owner);
 fail:
 	xenbus_dev_error(dev, err, "xenbus_dev_probe on %s", dev->nodename);
 	xenbus_switch_state(dev, XenbusStateClosed);
@@ -263,6 +272,8 @@ int xenbus_dev_remove(struct device *_dev)
 	if (drv->remove)
 		drv->remove(dev);
 
+	module_put(drv->driver.owner);
+
 	free_otherend_details(dev);
 
 	xenbus_switch_state(dev, XenbusStateClosed);