Re: [PATCH 4/5] xfs: consolidate attribute value copying

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

On Thu, Aug 29, 2019 at 09:35:04PM +1000, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> The same code is used to copy do the attribute copying in three
> different places. Consolidate them into a single function in
> preparation from on-demand buffer allocation.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>

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

--D

> ---
>  fs/xfs/libxfs/xfs_attr_leaf.c | 88 +++++++++++++++++++----------------
>  1 file changed, 49 insertions(+), 39 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> index 8085c4f0e5a0..f6a595e76343 100644
> --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> @@ -393,6 +393,44 @@ xfs_attr_namesp_match(int arg_flags, int ondisk_flags)
>  	return XFS_ATTR_NSP_ONDISK(ondisk_flags) == XFS_ATTR_NSP_ARGS_TO_ONDISK(arg_flags);
>  }
>  
> +static int
> +xfs_attr_copy_value(
> +	struct xfs_da_args	*args,
> +	unsigned char		*value,
> +	int			valuelen)
> +{
> +	/*
> +	 * No copy if all we have to do is get the length
> +	 */
> +	if (args->flags & ATTR_KERNOVAL) {
> +		args->valuelen = valuelen;
> +		return 0;
> +	}
> +
> +	/*
> +	 * No copy if the length of the existing buffer is too small
> +	 */
> +	if (args->valuelen < valuelen) {
> +		args->valuelen = valuelen;
> +		return -ERANGE;
> +	}
> +	args->valuelen = valuelen;
> +
> +	/* remote block xattr requires IO for copy-in */
> +	if (args->rmtblkno)
> +		return xfs_attr_rmtval_get(args);
> +
> +	/*
> +	 * This is to prevent a GCC warning because the remote xattr case
> +	 * doesn't have a value to pass in. In that case, we never reach here,
> +	 * but GCC can't work that out and so throws a "passing NULL to
> +	 * memcpy" warning.
> +	 */
> +	if (!value)
> +		return -EINVAL;
> +	memcpy(args->value, value, valuelen);
> +	return 0;
> +}
>  
>  /*========================================================================
>   * External routines when attribute fork size < XFS_LITINO(mp).
> @@ -727,11 +765,12 @@ xfs_attr_shortform_lookup(xfs_da_args_t *args)
>   * exist or we can't retrieve the value.
>   */
>  int
> -xfs_attr_shortform_getvalue(xfs_da_args_t *args)
> +xfs_attr_shortform_getvalue(
> +	struct xfs_da_args	*args)
>  {
> -	xfs_attr_shortform_t *sf;
> -	xfs_attr_sf_entry_t *sfe;
> -	int i;
> +	struct xfs_attr_shortform *sf;
> +	struct xfs_attr_sf_entry *sfe;
> +	int			i;
>  
>  	ASSERT(args->dp->i_afp->if_flags == XFS_IFINLINE);
>  	sf = (xfs_attr_shortform_t *)args->dp->i_afp->if_u1.if_data;
> @@ -744,18 +783,8 @@ xfs_attr_shortform_getvalue(xfs_da_args_t *args)
>  			continue;
>  		if (!xfs_attr_namesp_match(args->flags, sfe->flags))
>  			continue;
> -		if (args->flags & ATTR_KERNOVAL) {
> -			args->valuelen = sfe->valuelen;
> -			return 0;
> -		}
> -		if (args->valuelen < sfe->valuelen) {
> -			args->valuelen = sfe->valuelen;
> -			return -ERANGE;
> -		}
> -		args->valuelen = sfe->valuelen;
> -		memcpy(args->value, &sfe->nameval[args->namelen],
> -						    args->valuelen);
> -		return 0;
> +		return xfs_attr_copy_value(args, &sfe->nameval[args->namelen],
> +						sfe->valuelen);
>  	}
>  	return -ENOATTR;
>  }
> @@ -2368,7 +2397,6 @@ xfs_attr3_leaf_getvalue(
>  	struct xfs_attr_leaf_entry *entry;
>  	struct xfs_attr_leaf_name_local *name_loc;
>  	struct xfs_attr_leaf_name_remote *name_rmt;
> -	int			valuelen;
>  
>  	leaf = bp->b_addr;
>  	xfs_attr3_leaf_hdr_from_disk(args->geo, &ichdr, leaf);
> @@ -2380,18 +2408,9 @@ xfs_attr3_leaf_getvalue(
>  		name_loc = xfs_attr3_leaf_name_local(leaf, args->index);
>  		ASSERT(name_loc->namelen == args->namelen);
>  		ASSERT(memcmp(args->name, name_loc->nameval, args->namelen) == 0);
> -		valuelen = be16_to_cpu(name_loc->valuelen);
> -		if (args->flags & ATTR_KERNOVAL) {
> -			args->valuelen = valuelen;
> -			return 0;
> -		}
> -		if (args->valuelen < valuelen) {
> -			args->valuelen = valuelen;
> -			return -ERANGE;
> -		}
> -		args->valuelen = valuelen;
> -		memcpy(args->value, &name_loc->nameval[args->namelen], valuelen);
> -		return 0;
> +		return xfs_attr_copy_value(args,
> +					&name_loc->nameval[args->namelen],
> +					be16_to_cpu(name_loc->valuelen));
>  	}
>  
>  	name_rmt = xfs_attr3_leaf_name_remote(leaf, args->index);
> @@ -2401,16 +2420,7 @@ xfs_attr3_leaf_getvalue(
>  	args->rmtblkno = be32_to_cpu(name_rmt->valueblk);
>  	args->rmtblkcnt = xfs_attr3_rmt_blocks(args->dp->i_mount,
>  					       args->rmtvaluelen);
> -	if (args->flags & ATTR_KERNOVAL) {
> -		args->valuelen = args->rmtvaluelen;
> -		return 0;
> -	}
> -	if (args->valuelen < args->rmtvaluelen) {
> -		args->valuelen = args->rmtvaluelen;
> -		return -ERANGE;
> -	}
> -	args->valuelen = args->rmtvaluelen;
> -	return xfs_attr_rmtval_get(args);
> +	return xfs_attr_copy_value(args, NULL, args->rmtvaluelen);
>  }
>  
>  /*========================================================================
> -- 
> 2.23.0.rc1
>