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

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Message-ID: <20061130072058.GA18004@wotan.suse.de>
Date:	Thu, 30 Nov 2006 08:20:58 +0100
From:	Nick Piggin <npiggin@...e.de>
To:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, linux-fsdevel@...r.kernel.org
Subject: [patch 1/3] mm: pagecache write deadlocks zerolength fix


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

Signed-off-by: Nick Piggin <npiggin@...e.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;
-
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