On 5.12.18 г. 14:28 ч., Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
> ---
> 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)
nit: I think it's better if you rename the iterator variable to "iter".
>
> 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);
Shouldn't this be em->len - (pos - em->start) since this gives the
remaining length of the extent? Isn't pos guaranteed to be >= em->start ?
> + ret = iov_iter_zero(zero_len, to);
> + } else {
> + ret = em_dax_rw(inode, em, pos, len, to);
> + }
> if (ret < 0)
> goto out;
> pos += ret;
>
