From 0df76f5ecc4bb65fcc5a63399900acec672b9fbd Mon Sep 17 00:00:00 2001
From: Chris Mason <chris.mason@oracle.com>
Date: Mon, 7 Mar 2011 11:10:24 -0500
Subject: [PATCH] --- yaml --- r: 234090 b: refs/heads/master c:
 31339acd07b4ba687906702085127895a56eb920 h: refs/heads/master v: v3

---
 [refs]                |  2 +-
 trunk/fs/btrfs/file.c | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index 3a05bfc17da5..c3d09b791aad 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: b1bf862e9dad431175a1174379476299dbfdc017
+refs/heads/master: 31339acd07b4ba687906702085127895a56eb920
diff --git a/trunk/fs/btrfs/file.c b/trunk/fs/btrfs/file.c
index 13664b315fe2..ab22ca4f237f 100644
--- a/trunk/fs/btrfs/file.c
+++ b/trunk/fs/btrfs/file.c
@@ -69,6 +69,19 @@ static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
 
 		/* Flush processor's dcache for this page */
 		flush_dcache_page(page);
+
+		/*
+		 * if we get a partial write, we can end up with
+		 * partially up to date pages.  These add
+		 * a lot of complexity, so make sure they don't
+		 * happen by forcing this copy to be retried.
+		 *
+		 * The rest of the btrfs_file_write code will fall
+		 * back to page at a time copies after we return 0.
+		 */
+		if (!PageUptodate(page) && copied < count)
+			copied = 0;
+
 		iov_iter_advance(i, copied);
 		write_bytes -= copied;
 		total_copied += copied;