[PATCH 03/10] btrfs: dax: read zeros from holes

[Goldwyn Rodrigues]

From: Goldwyn Rodrigues <rgold...@suse.com>

Signed-off-by: Goldwyn Rodrigues <rgold...@suse.com>
---
 fs/btrfs/dax.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/dax.c b/fs/btrfs/dax.c
index d614bf73bf8e..5a297674adec 100644
--- a/fs/btrfs/dax.c
+++ b/fs/btrfs/dax.c
@@ -54,7 +54,12 @@ ssize_t btrfs_file_dax_read(struct kiocb *iocb, struct 
iov_iter *to)
 
                 BUG_ON(em->flags & EXTENT_FLAG_FS_MAPPING);
 
-                ret = em_dax_rw(inode, em, pos, len, to);
+               if (em->block_start == EXTENT_MAP_HOLE) {
+                       u64 zero_len = min(em->len - (em->start - pos), len);
+                       ret = iov_iter_zero(zero_len, to);
+               } else {
+                       ret = em_dax_rw(inode, em, pos, len, to);
+               }
                 if (ret < 0)
                         goto out;
                 pos += ret;
-- 
2.16.4