diff --git a/ChangeLog b/ChangeLog
index 71e236906a4..c00de77a9a5 100755
--- a/ChangeLog
+++ b/ChangeLog
@@ -10882,9 +10882,11 @@
 	* networking:  Correct return value from psock_tcp_accept().  From
 	  SaeHie Park (2015-08-25).
 	* drivers/mtd/st25fl1.c: Add a driver for ST25L1*K QuadSPI parts
-	  (2015-08-15).
+	  (2015-08-25).
 	* include/nuttx/spi/qspi.h:  Develop a new interface for QSPI, at
 	  least the way that QSPI is implemented on the SAMV71.  Originally
 	  planned to use the SPI interface, but it is just now compatible
-	  with the SAMV71 QSPI hardware (2015-08-15).
+	  with the SAMV71 QSPI hardware (2015-08-25).
+	* drivers/rwbuffer.c: Fix some logic errors.  From Dmitry Nikolaev
+	  via Juha Niskanen (2015-08-26).
 
diff --git a/arch b/arch
index 463d5c9af87..5336c646386 160000
--- a/arch
+++ b/arch
@@ -1 +1 @@
-Subproject commit 463d5c9af87cb0e749f7400ae1a1dfe0d56517fc
+Subproject commit 5336c646386607424e3426fb488d73241abb5f08
diff --git a/drivers/net/loopback.c b/drivers/net/loopback.c
index 5e2a12d1e38..83aa9836579 100644
--- a/drivers/net/loopback.c
+++ b/drivers/net/loopback.c
@@ -49,6 +49,7 @@
 #include <debug.h>
 
 #include <arpa/inet.h>
+#include <net/if.h>
 
 #include <nuttx/arch.h>
 #include <nuttx/irq.h>
@@ -532,13 +533,16 @@ int localhost_initialize(void)
   net_ipv4addr_copy(priv->lo_dev.d_draddr, g_lo_ipv4addr);
   net_ipv4addr_copy(priv->lo_dev.d_netmask, g_lo_ipv4mask);
 #endif
+
 #ifdef CONFIG_NET_IPv6
  net_ipv6addr_copy(priv->lo_dev.d_ipv6addr, g_lo_ipv6addr);
  net_ipv6addr_copy(priv->lo_dev.d_ipv6draddr, g_lo_ipv6addr);
  net_ipv6addr_copy(priv->lo_dev.d_ipv6netmask, g_ipv6_alloneaddr);
 #endif
+
   /* Put the network in the UP state */
 
+  priv->lo_dev.d_flags = IFF_UP;
   return lo_ifup(&priv->lo_dev);
 }
 
diff --git a/drivers/rwbuffer.c b/drivers/rwbuffer.c
index fd2f73c77ae..9c443df7b59 100644
--- a/drivers/rwbuffer.c
+++ b/drivers/rwbuffer.c
@@ -96,7 +96,7 @@ static void rwb_semtake(sem_t *sem)
 
   while (sem_wait(sem) != 0)
     {
-      /* The only case that an error should occr here is if
+      /* The only case that an error should occur here is if
        * the wait was awakened by a signal.
        */
 
@@ -117,8 +117,8 @@ static void rwb_semtake(sem_t *sem)
 static inline bool rwb_overlap(off_t blockstart1, size_t nblocks1,
                                off_t blockstart2, size_t nblocks2)
 {
-  off_t blockend1 = blockstart1 + nblocks1;
-  off_t blockend2 = blockstart2 + nblocks2;
+  off_t blockend1 = blockstart1 + nblocks1 - 1;
+  off_t blockend2 = blockstart2 + nblocks2 - 1;
 
   /* If the buffer 1 is wholly outside of buffer 2, return false */
 
@@ -257,7 +257,7 @@ static ssize_t rwb_writebuffer(FAR struct rwbuffer_s *rwb,
 
       /* Flush the write buffer */
 
-      ret = rwb->wrflush(rwb, rwb->wrbuffer, rwb->wrblockstart, rwb->wrnblocks);
+      ret = rwb->wrflush(rwb->dev, rwb->wrbuffer, rwb->wrblockstart, rwb->wrnblocks);
       if (ret < 0)
         {
           fdbg("ERROR: Error writing multiple from cache: %d\n", -ret);
@@ -842,7 +842,7 @@ int rwb_read(FAR struct rwbuffer_s *rwb, off_t startblock, uint32_t nblocks,
        * the user buffer.
        */
 
-      ret = rwb->rhreload(rwb->dev, startblock, nblocks, rdbuffer);
+      ret = rwb->rhreload(rwb->dev, rdbuffer, startblock, nblocks);
     }
 #endif
 
diff --git a/fs/vfs/fs_poll.c b/fs/vfs/fs_poll.c
index 10852e7d910..f13148288c8 100644
--- a/fs/vfs/fs_poll.c
+++ b/fs/vfs/fs_poll.c
@@ -49,6 +49,7 @@
 #include <nuttx/clock.h>
 #include <nuttx/fs/fs.h>
 #include <nuttx/net/net.h>
+#include <nuttx/semaphore.h>
 
 #include <arch/irq.h>
 
@@ -326,8 +327,6 @@ int file_poll(int fd, FAR struct pollfd *fds, bool setup)
 
 int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
 {
-  struct timespec abstime;
-  irqstate_t flags;
   sem_t sem;
   int count = 0;
   int ret;
diff --git a/net/netdev/netdev_register.c b/net/netdev/netdev_register.c
index 362e5a44a25..de5fa6c8f43 100644
--- a/net/netdev/netdev_register.c
+++ b/net/netdev/netdev_register.c
@@ -257,16 +257,35 @@ int netdev_register(FAR struct net_driver_s *dev, enum net_lltype_e lltype)
       dev->d_conncb = NULL;
       dev->d_devcb = NULL;
 
-      /* Get the next available device number and sssign a device name to
+      /* Get the next available device number and assign a device name to
        * the interface
        */
 
       save = net_lock();
+
 #ifdef CONFIG_NET_MULTILINK
-      devnum = find_devnum(devfmt);
+#  ifdef CONFIG_NET_LOOPBACK
+      /* The local loopback device is a special case:  There can be only one
+       * local loopback device so it is unnumbered.
+       */
+
+      if (lltype == NET_LL_LOOPBACK)
+        {
+          devnum = 0;
+        }
+      else
+#  endif
+        {
+          devnum = find_devnum(devfmt);
+        }
 #else
+      /* There is only a single link type.  Finding the next network device
+       * number is simple.
+       */
+
       devnum = g_next_devnum++;
 #endif
+
 #ifdef CONFIG_NET_USER_DEVFMT
       if (*dev->d_ifname)
         {
diff --git a/net/tcp/tcp_appsend.c b/net/tcp/tcp_appsend.c
index 4f110f848a9..ab799d975a9 100644
--- a/net/tcp/tcp_appsend.c
+++ b/net/tcp/tcp_appsend.c
@@ -172,7 +172,7 @@ void tcp_appsend(FAR struct net_driver_s *dev, FAR struct tcp_conn_s *conn,
   else
     {
 #ifdef CONFIG_NET_TCP_WRITE_BUFFERS
-      DEBUGASSERT(dev->d_sndlen >= 0 && dev->d_sndlen <= conn->mss);
+      DEBUGASSERT(dev->d_sndlen <= conn->mss);
 #else
       /* If d_sndlen > 0, the application has data to be sent. */