Re: [PATCH 4/4] xfs: precalculate default inode attribute offset

["Darrick J. Wong" <djwong@kernel.org>]

On Tue, Mar 30, 2021 at 04:30:59PM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Default attr fork offset is based on inode size, so is a fixed
> geometry parameter of the inode. Move it to the xfs_ino_geometry
> structure and stop calculating it on every call to
> xfs_default_attroffset().
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/libxfs/xfs_bmap.c   | 21 ++++++++++-----------
>  fs/xfs/libxfs/xfs_bmap.h   |  1 +
>  fs/xfs/libxfs/xfs_shared.h |  4 ++++
>  fs/xfs/xfs_mount.c         | 14 +++++++++++++-
>  4 files changed, 28 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index 16c8730c140f..7930f11e4c54 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -94,6 +94,15 @@ xfs_bmap_compute_maxlevels(
>  	mp->m_bm_maxlevels[whichfork] = level;
>  }
>  
> +unsigned int
> +xfs_bmap_compute_attr_offset(
> +	struct xfs_mount	*mp)
> +{
> +	if (mp->m_sb.sb_inodesize == 256)
> +		return XFS_LITINO(mp) - XFS_BMDR_SPACE_CALC(MINABTPTRS);
> +	return XFS_BMDR_SPACE_CALC(6 * MINABTPTRS);
> +}
> +
>  STATIC int				/* error */
>  xfs_bmbt_lookup_eq(
>  	struct xfs_btree_cur	*cur,
> @@ -192,19 +201,9 @@ uint
>  xfs_default_attroffset(
>  	struct xfs_inode	*ip)
>  {
> -	struct xfs_mount	*mp = ip->i_mount;
> -	uint			offset;
> -
>  	if (ip->i_df.if_format == XFS_DINODE_FMT_DEV)
>  		return roundup(sizeof(xfs_dev_t), 8);
> -
> -	if (mp->m_sb.sb_inodesize == 256)
> -		offset = XFS_LITINO(mp) - XFS_BMDR_SPACE_CALC(MINABTPTRS);
> -	else
> -		offset = XFS_BMDR_SPACE_CALC(6 * MINABTPTRS);
> -
> -	ASSERT(offset < XFS_LITINO(mp));
> -	return offset;
> +	return M_IGEO(ip->i_mount)->attr_fork_offset;
>  }
>  
>  /*
> diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
> index 6747e97a7949..a49df4092c30 100644
> --- a/fs/xfs/libxfs/xfs_bmap.h
> +++ b/fs/xfs/libxfs/xfs_bmap.h
> @@ -185,6 +185,7 @@ static inline bool xfs_bmap_is_written_extent(struct xfs_bmbt_irec *irec)
>  
>  void	xfs_trim_extent(struct xfs_bmbt_irec *irec, xfs_fileoff_t bno,
>  		xfs_filblks_t len);
> +unsigned int xfs_bmap_compute_attr_offset(struct xfs_mount *mp);
>  int	xfs_bmap_add_attrfork(struct xfs_inode *ip, int size, int rsvd);
>  int	xfs_bmap_set_attrforkoff(struct xfs_inode *ip, int size, int *version);
>  void	xfs_bmap_local_to_extents_empty(struct xfs_trans *tp,
> diff --git a/fs/xfs/libxfs/xfs_shared.h b/fs/xfs/libxfs/xfs_shared.h
> index 8c61a461bf7b..782fdd08f759 100644
> --- a/fs/xfs/libxfs/xfs_shared.h
> +++ b/fs/xfs/libxfs/xfs_shared.h
> @@ -176,8 +176,12 @@ struct xfs_ino_geometry {
>  
>  	unsigned int	agino_log;	/* #bits for agino in inum */
>  
> +	/* precomputed default inode attribute fork offset */
> +	unsigned int	attr_fork_offset;
> +
>  	/* precomputed value for di_flags2 */
>  	uint64_t	new_diflags2;
> +
>  };
>  
>  #endif /* __XFS_SHARED_H__ */
> diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
> index 1c97b155a8ee..cb1e2c4702c3 100644
> --- a/fs/xfs/xfs_mount.c
> +++ b/fs/xfs/xfs_mount.c
> @@ -675,6 +675,18 @@ xfs_unmount_flush_inodes(
>  	xfs_health_unmount(mp);
>  }
>  
> +static void
> +xfs_mount_setup_inode_geom(
> +	struct xfs_mount	*mp)
> +{
> +	struct xfs_ino_geometry *igeo = M_IGEO(mp);
> +
> +	igeo->attr_fork_offset = xfs_bmap_compute_attr_offset(mp);
> +	ASSERT(igeo->attr_fork_offset < XFS_LITINO(mp));

Why not put these statements at the bottom of xfs_ialloc_setup_geometry
and avoid creating an extra function?

--D

> +
> +	xfs_ialloc_setup_geometry(mp);
> +}
> +
>  /*
>   * This function does the following on an initial mount of a file system:
>   *	- reads the superblock from disk and init the mount struct
> @@ -758,7 +770,7 @@ xfs_mountfs(
>  	xfs_alloc_compute_maxlevels(mp);
>  	xfs_bmap_compute_maxlevels(mp, XFS_DATA_FORK);
>  	xfs_bmap_compute_maxlevels(mp, XFS_ATTR_FORK);
> -	xfs_ialloc_setup_geometry(mp);
> +	xfs_mount_setup_inode_geom(mp);
>  	xfs_rmapbt_compute_maxlevels(mp);
>  	xfs_refcountbt_compute_maxlevels(mp);
>  
> -- 
> 2.31.0
>