Re: [PATCH 1/3] xfs: Introduce xfs_iext_max() helper

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Mon, Aug 31, 2020 at 06:30:08PM +0530, Chandan Babu R wrote:
> xfs_iext_max() returns the maximum number of extents possible for either
> data fork or attribute fork. This helper will be extended further in a
> future commit when maximum extent counts associated with data/attribute
> forks are increased.
> 
> No functional changes have been made.

Hmm....

> Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
> ---
>  fs/xfs/libxfs/xfs_bmap.c       |  9 ++++-----
>  fs/xfs/libxfs/xfs_inode_buf.c  |  8 +++-----
>  fs/xfs/libxfs/xfs_inode_fork.h | 10 ++++++++++
>  3 files changed, 17 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
> index dcc8eeecd571..16b983b8977d 100644
> --- a/fs/xfs/libxfs/xfs_bmap.c
> +++ b/fs/xfs/libxfs/xfs_bmap.c
> @@ -74,13 +74,12 @@ xfs_bmap_compute_maxlevels(
>  	 * for both ATTR1 and ATTR2 we have to assume the worst case scenario
>  	 * of a minimum size available.
>  	 */
> -	if (whichfork == XFS_DATA_FORK) {
> -		maxleafents = MAXEXTNUM;
> +	maxleafents = xfs_iext_max(&mp->m_sb, whichfork);
> +	if (whichfork == XFS_DATA_FORK)
>  		sz = XFS_BMDR_SPACE_CALC(MINDBTPTRS);
> -	} else {
> -		maxleafents = MAXAEXTNUM;
> +	else
>  		sz = XFS_BMDR_SPACE_CALC(MINABTPTRS);
> -	}
> +
>  	maxrootrecs = xfs_bmdr_maxrecs(sz, 0);
>  	minleafrecs = mp->m_bmap_dmnr[0];
>  	minnoderecs = mp->m_bmap_dmnr[1];
> diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
> index 8d5dd08eab75..5dcd71bfab2e 100644
> --- a/fs/xfs/libxfs/xfs_inode_buf.c
> +++ b/fs/xfs/libxfs/xfs_inode_buf.c
> @@ -369,6 +369,7 @@ xfs_dinode_verify_fork(
>  	int			whichfork)
>  {
>  	uint32_t		di_nextents = XFS_DFORK_NEXTENTS(dip, whichfork);
> +	xfs_extnum_t		max_extents;
>  
>  	switch (XFS_DFORK_FORMAT(dip, whichfork)) {
>  	case XFS_DINODE_FMT_LOCAL:
> @@ -390,12 +391,9 @@ xfs_dinode_verify_fork(
>  			return __this_address;
>  		break;
>  	case XFS_DINODE_FMT_BTREE:
> -		if (whichfork == XFS_ATTR_FORK) {
> -			if (di_nextents > MAXAEXTNUM)
> -				return __this_address;
> -		} else if (di_nextents > MAXEXTNUM) {
> +		max_extents = xfs_iext_max(&mp->m_sb, whichfork);
> +		if (di_nextents > max_extents)
>  			return __this_address;
> -		}
>  		break;
>  	default:
>  		return __this_address;
> diff --git a/fs/xfs/libxfs/xfs_inode_fork.h b/fs/xfs/libxfs/xfs_inode_fork.h
> index 4219b01f1034..75e07078967e 100644
> --- a/fs/xfs/libxfs/xfs_inode_fork.h
> +++ b/fs/xfs/libxfs/xfs_inode_fork.h
> @@ -153,6 +153,16 @@ static inline int8_t xfs_ifork_format(struct xfs_ifork *ifp)
>  	return ifp->if_format;
>  }
>  
> +static inline xfs_extnum_t xfs_iext_max(struct xfs_sb *sbp, int whichfork)
> +{
> +	ASSERT(whichfork == XFS_DATA_FORK || whichfork == XFS_ATTR_FORK);
> +
> +	if (whichfork == XFS_DATA_FORK)
> +		return MAXEXTNUM;
> +	else
> +		return MAXAEXTNUM;

...I kinda wish you /had/ made the functional change to make this return
MAXEXTNUM for cow forks, even if none of the callers actually care. :)

--D

> +}
> +
>  struct xfs_ifork *xfs_iext_state_to_fork(struct xfs_inode *ip, int state);
>  
>  int		xfs_iformat_data_fork(struct xfs_inode *, struct xfs_dinode *);
> -- 
> 2.28.0
>