ext2: Avoid DAX zeroing to corrupt data

Currently ext2 zeroes any data blocks allocated for DAX inode however it
still returns them as BH_New. Thus DAX code zeroes them again in
dax_insert_mapping() which can possibly overwrite the data that has been
already stored to those blocks by a racing dax_io(). Avoid marking
pre-zeroed buffers as new.

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index 038d0ed5f565..9a14af3b1a69 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -745,11 +745,11 @@ static int ext2_get_blocks(struct inode *inode,
                         mutex_unlock(&ei->truncate_mutex);
                         goto cleanup;
                 }
-        }
+        } else
+                set_buffer_new(bh_result);
 
         ext2_splice_branch(inode, iblock, partial, indirect_blks, count);
         mutex_unlock(&ei->truncate_mutex);
-        set_buffer_new(bh_result);
 got_it:
         map_bh(bh_result, inode->i_sb, le32_to_cpu(chain[depth-1].key));
         if (count > blocks_to_boundary)