[PATCH 2/3] ext4: Clear the unwritten buffer_head flag properly

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

ext4_get_blocks_wrap does a block lookup requesting to
allocate new blocks. A lookup of blocks in prealloc area
result in setting the unwritten flag in buffer_head. So
a write to an unwritten extent will cause the buffer_head
to have unwritten and mapped flag set. Clear hte unwritten
buffer_head flag before requesting to allocate blocks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 fs/ext4/inode.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c3cd00f..f6d7e9b 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1149,6 +1149,7 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
 	int retval;
 
 	clear_buffer_mapped(bh);
+	clear_buffer_unwritten(bh);
 
 	/*
 	 * Try to see if we can get  the block without requesting
@@ -1179,6 +1180,12 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
 		return retval;
 
 	/*
+	 * The above get_blocks can cause the buffer to be
+	 * marked unwritten. So clear the same.
+	 */
+	clear_buffer_unwritten(bh);
+
+	/*
 	 * New blocks allocate and/or writing to uninitialized extent
 	 * will possibly result in updating i_data, so we take
 	 * the write lock of i_data_sem, and call get_blocks()
-- 
1.6.3.rc4