[patch 1/3] mm: pagecache write deadlocks zerolength fix

[Nick Piggin <npiggin@suse.de>]

writev with a zero-length segment is a noop, and we shouldn't return EFAULT.

Signed-off-by: Nick Piggin <npiggin@suse.de>

Index: linux-2.6/include/linux/pagemap.h
===================================================================
--- linux-2.6.orig/include/linux/pagemap.h
+++ linux-2.6/include/linux/pagemap.h
@@ -198,6 +198,9 @@ static inline int fault_in_pages_writeab
 {
 	int ret;
 
+	if (unlikely(size == 0))
+		return 0;
+
 	/*
 	 * Writing zeroes into userspace here is OK, because we know that if
 	 * the zero gets there, we'll be overwriting it.
@@ -222,6 +225,9 @@ static inline int fault_in_pages_readabl
 	volatile char c;
 	int ret;
 
+	if (unlikely(size == 0))
+		return 0;
+
 	ret = __get_user(c, uaddr);
 	if (ret == 0) {
 		const char __user *end = uaddr + size - 1;