Re: [PATCH 4/5] dax: use sb_issue_zerout instead of calling dax_clear_sectors

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Thu, Mar 24, 2016 at 05:17:29PM -0600, Vishal Verma wrote:
> @@ -72,16 +72,7 @@ xfs_zero_extent(
>       struct xfs_mount *mp = ip->i_mount;
>       xfs_daddr_t     sector = xfs_fsb_to_db(ip, start_fsb);
>       sector_t        block = XFS_BB_TO_FSBT(mp, sector);
> -     ssize_t         size = XFS_FSB_TO_B(mp, count_fsb);
>  
> -     if (IS_DAX(VFS_I(ip)))
> -             return dax_clear_sectors(xfs_find_bdev_for_inode(VFS_I(ip)),
> -                             sector, size);
> -
> -     /*
> -      * let the block layer decide on the fastest method of
> -      * implementing the zeroing.
> -      */
>       return sb_issue_zeroout(mp->m_super, block, count_fsb, GFP_NOFS);

While not new: using sb_issue_zeroout in XFS is wrong as it doesn't
account for the RT device.  We need the xfs_find_bdev_for_inode and
call blkdev_issue_zeroout directly with the bdev it returned.