Re: [PATCH 09/11] ext4: Rip out DAX handling from direct IO path

[Ross Zwisler <ross.zwisler@linux.intel.com>]

On Tue, Nov 08, 2016 at 12:08:15PM +0100, Jan Kara wrote:
> Reads and writes for DAX inodes should no longer end up in direct IO
> code. Rip out the support and add a warning.
> 
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/ext4/inode.c | 49 +++++++++++++++----------------------------------
>  1 file changed, 15 insertions(+), 34 deletions(-)
> 
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 4d71c7bc3524..72886e3bf0d3 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3594,19 +3594,7 @@ static ssize_t ext4_direct_IO_write(struct kiocb *iocb, struct iov_iter *iter)
>  	iocb->private = NULL;
>  	if (overwrite)
>  		get_block_func = ext4_dio_get_block_overwrite;
> -	else if (IS_DAX(inode)) {
> -		/*
> -		 * We can avoid zeroing for aligned DAX writes beyond EOF. Other
> -		 * writes need zeroing either because they can race with page
> -		 * faults or because they use partial blocks.
> -		 */
> -		if (round_down(offset, 1<<inode->i_blkbits) >= inode->i_size &&
> -		    ext4_aligned_io(inode, offset, count))
> -			get_block_func = ext4_dio_get_block;
> -		else
> -			get_block_func = ext4_dax_get_block;

This was the last use of ext4_dax_get_block(), so that function can safely be
removed.  I can do that in a separate patch, if you don't want to pull it into
this set.

Otherwise this looks correct to me.

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>