3 files changed, 18 insertions, 8 deletions

diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index 3822b4f49c84..7bd7c45b53ef 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -305,6 +305,9 @@ static int num_force_kipmid;
 #ifdef CONFIG_PCI
 static int pci_registered;
 #endif
+#ifdef CONFIG_ACPI
+static int pnp_registered;
+#endif
 #ifdef CONFIG_PPC_OF
 static int of_registered;
 #endif
@@ -2126,7 +2129,7 @@ static int __devinit ipmi_pnp_probe(struct pnp_dev *dev,
 {
         struct acpi_device *acpi_dev;
         struct smi_info *info;
-        struct resource *res;
+        struct resource *res, *res_second;
         acpi_handle handle;
         acpi_status status;
         unsigned long long tmp;
@@ -2182,13 +2185,13 @@ static int __devinit ipmi_pnp_probe(struct pnp_dev *dev,
         info->io.addr_data = res->start;
 
         info->io.regspacing = DEFAULT_REGSPACING;
-        res = pnp_get_resource(dev,
+        res_second = pnp_get_resource(dev,
                                (info->io.addr_type == IPMI_IO_ADDR_SPACE) ?
                                         IORESOURCE_IO : IORESOURCE_MEM,
                                1);
-        if (res) {
-                if (res->start > info->io.addr_data)
-                        info->io.regspacing = res->start - info->io.addr_data;
+        if (res_second) {
+                if (res_second->start > info->io.addr_data)
+                        info->io.regspacing = res_second->start - info->io.addr_data;
         }
         info->io.regsize = DEFAULT_REGSPACING;
         info->io.regshift = 0;
@@ -3359,6 +3362,7 @@ static __devinit int init_ipmi_si(void)
 
 #ifdef CONFIG_ACPI
         pnp_register_driver(&ipmi_pnp_driver);
+        pnp_registered = 1;
 #endif
 
 #ifdef CONFIG_DMI
@@ -3526,7 +3530,8 @@ static __exit void cleanup_ipmi_si(void)
                 pci_unregister_driver(&ipmi_pci_driver);
 #endif
 #ifdef CONFIG_ACPI
-        pnp_unregister_driver(&ipmi_pnp_driver);
+        if (pnp_registered)
+                pnp_unregister_driver(&ipmi_pnp_driver);
 #endif
 
 #ifdef CONFIG_PPC_OF
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index a398ecdbd758..1f528fad3516 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -788,10 +788,11 @@ static const struct file_operations zero_fops = {
 /*
  * capabilities for /dev/zero
  * - permits private mappings, "copies" are taken of the source of zeros
+ * - no writeback happens
  */
 static struct backing_dev_info zero_bdi = {
         .name           = "char/mem",
-        .capabilities   = BDI_CAP_MAP_COPY,
+        .capabilities   = BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK,
 };
 
 static const struct file_operations full_fops = {
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 942a9826bd23..c810481a5bc2 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -596,6 +596,10 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
         ssize_t ret;
         bool nonblock;
 
+        /* Userspace could be out to fool us */
+        if (!count)
+                return 0;
+
         port = filp->private_data;
 
         nonblock = filp->f_flags & O_NONBLOCK;
@@ -642,7 +646,7 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
         poll_wait(filp, &port->waitqueue, wait);
 
         ret = 0;
-        if (port->inbuf)
+        if (!will_read_block(port))
                 ret |= POLLIN | POLLRDNORM;
         if (!will_write_block(port))
                 ret |= POLLOUT;