Re: [PATCH v9 14/24] xfs: Add helpers xfs_attr_is_shortform and xfs_attr_set_shortform

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

On Thu, Apr 30, 2020 at 03:50:06PM -0700, Allison Collins wrote:
> In this patch, we hoist code from xfs_attr_set_args into two new helpers
> xfs_attr_is_shortform and xfs_attr_set_shortform.  These two will help
> to simplify xfs_attr_set_args when we get into delayed attrs later.
> 
> Signed-off-by: Allison Collins <allison.henderson@oracle.com>
> Reviewed-by: Brian Foster <bfoster@redhat.com>
> Reviewed-by: Chandan Rajendra <chandanrlinux@gmail.com>

Looks ok to me,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/libxfs/xfs_attr.c | 107 +++++++++++++++++++++++++++++++----------------
>  1 file changed, 72 insertions(+), 35 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> index af47566..d112910 100644
> --- a/fs/xfs/libxfs/xfs_attr.c
> +++ b/fs/xfs/libxfs/xfs_attr.c
> @@ -204,6 +204,66 @@ xfs_attr_try_sf_addname(
>  }
>  
>  /*
> + * Check to see if the attr should be upgraded from non-existent or shortform to
> + * single-leaf-block attribute list.
> + */
> +static inline bool
> +xfs_attr_is_shortform(
> +	struct xfs_inode    *ip)
> +{
> +	return ip->i_d.di_aformat == XFS_DINODE_FMT_LOCAL ||
> +	       (ip->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
> +	        ip->i_d.di_anextents == 0);
> +}
> +
> +/*
> + * Attempts to set an attr in shortform, or converts short form to leaf form if
> + * there is not enough room.  If the attr is set, the transaction is committed
> + * and set to NULL.
> + */
> +STATIC int
> +xfs_attr_set_shortform(
> +	struct xfs_da_args	*args,
> +	struct xfs_buf		**leaf_bp)
> +{
> +	struct xfs_inode	*dp = args->dp;
> +	int			error, error2 = 0;
> +
> +	/*
> +	 * Try to add the attr to the attribute list in the inode.
> +	 */
> +	error = xfs_attr_try_sf_addname(dp, args);
> +	if (error != -ENOSPC) {
> +		error2 = xfs_trans_commit(args->trans);
> +		args->trans = NULL;
> +		return error ? error : error2;
> +	}
> +	/*
> +	 * It won't fit in the shortform, transform to a leaf block.  GROT:
> +	 * another possible req'mt for a double-split btree op.
> +	 */
> +	error = xfs_attr_shortform_to_leaf(args, leaf_bp);
> +	if (error)
> +		return error;
> +
> +	/*
> +	 * Prevent the leaf buffer from being unlocked so that a concurrent AIL
> +	 * push cannot grab the half-baked leaf buffer and run into problems
> +	 * with the write verifier. Once we're done rolling the transaction we
> +	 * can release the hold and add the attr to the leaf.
> +	 */
> +	xfs_trans_bhold(args->trans, *leaf_bp);
> +	error = xfs_defer_finish(&args->trans);
> +	xfs_trans_bhold_release(args->trans, *leaf_bp);
> +	if (error) {
> +		xfs_trans_brelse(args->trans, *leaf_bp);
> +		return error;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
>   * Set the attribute specified in @args.
>   */
>  int
> @@ -212,48 +272,25 @@ xfs_attr_set_args(
>  {
>  	struct xfs_inode	*dp = args->dp;
>  	struct xfs_buf          *leaf_bp = NULL;
> -	int			error, error2 = 0;
> +	int			error = 0;
>  
>  	/*
> -	 * If the attribute list is non-existent or a shortform list,
> -	 * upgrade it to a single-leaf-block attribute list.
> +	 * If the attribute list is already in leaf format, jump straight to
> +	 * leaf handling.  Otherwise, try to add the attribute to the shortform
> +	 * list; if there's no room then convert the list to leaf format and try
> +	 * again.
>  	 */
> -	if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL ||
> -	    (dp->i_d.di_aformat == XFS_DINODE_FMT_EXTENTS &&
> -	     dp->i_d.di_anextents == 0)) {
> +	if (xfs_attr_is_shortform(dp)) {
>  
>  		/*
> -		 * Try to add the attr to the attribute list in the inode.
> +		 * If the attr was successfully set in shortform, the
> +		 * transaction is committed and set to NULL.  Otherwise, is it
> +		 * converted from shortform to leaf, and the transaction is
> +		 * retained.
>  		 */
> -		error = xfs_attr_try_sf_addname(dp, args);
> -		if (error != -ENOSPC) {
> -			error2 = xfs_trans_commit(args->trans);
> -			args->trans = NULL;
> -			return error ? error : error2;
> -		}
> -
> -		/*
> -		 * It won't fit in the shortform, transform to a leaf block.
> -		 * GROT: another possible req'mt for a double-split btree op.
> -		 */
> -		error = xfs_attr_shortform_to_leaf(args, &leaf_bp);
> -		if (error)
> -			return error;
> -
> -		/*
> -		 * Prevent the leaf buffer from being unlocked so that a
> -		 * concurrent AIL push cannot grab the half-baked leaf
> -		 * buffer and run into problems with the write verifier.
> -		 * Once we're done rolling the transaction we can release
> -		 * the hold and add the attr to the leaf.
> -		 */
> -		xfs_trans_bhold(args->trans, leaf_bp);
> -		error = xfs_defer_finish(&args->trans);
> -		xfs_trans_bhold_release(args->trans, leaf_bp);
> -		if (error) {
> -			xfs_trans_brelse(args->trans, leaf_bp);
> +		error = xfs_attr_set_shortform(args, &leaf_bp);
> +		if (error || !args->trans)
>  			return error;
> -		}
>  	}
>  
>  	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> -- 
> 2.7.4
>