[RFC PATCH] mark buffer_head mapping preallocate area as new during write_begin with delayed allocation

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

We need to mark the  buffer_head mapping prealloc space
as new during write_begin. Otherwise we don't zero out the
page cache content properly for a partial write. This will
cause file corruption with preallocation.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

---
 fs/ext4/inode.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c6bd6ce..c7251ec 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2323,6 +2323,8 @@ static int ext4_da_get_block_prep(struct inode *inode, sector_t iblock,
 		set_buffer_delay(bh_result);
 	} else if (ret > 0) {
 		bh_result->b_size = (ret << inode->i_blkbits);
+		if (buffer_unwritten(bh_result))
+			set_buffer_new(bh_result);
 		ret = 0;
 	}
 
-- 
tg: (51bec03..) preallocate_corruption (depends on: ext4_lock_group_conversion)