Re: [PATCH] xfs: add FALLOC_FL_WRITE_ZEROES to XFS code base

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

On Tue, Oct 21, 2025 at 04:17:44PM +0200, Lukas Herbolt wrote:
> Add support for FALLOC_FL_WRITE_ZEROES if the underlying device enable
> the unmap write zeroes operation.
> 
> Signed-off-by: Lukas Herbolt <lukas@herbolt.com>
> ---
>  fs/xfs/xfs_bmap_util.c |  6 +++---
>  fs/xfs/xfs_bmap_util.h |  4 ++--
>  fs/xfs/xfs_file.c      | 25 ++++++++++++++++++-------
>  3 files changed, 23 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 06ca11731e430..fd43c9db79a8d 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -645,6 +645,7 @@ xfs_free_eofblocks(
>  int
>  xfs_alloc_file_space(
>  	struct xfs_inode	*ip,
> +	uint32_t		flags,		/* XFS_BMAPI_... */
>  	xfs_off_t		offset,
>  	xfs_off_t		len)
>  {
> @@ -747,9 +748,8 @@ xfs_alloc_file_space(
>  		 * startoffset_fsb so that one of the following allocations
>  		 * will eventually reach the requested range.
>  		 */
> -		error = xfs_bmapi_write(tp, ip, startoffset_fsb,
> -				allocatesize_fsb, XFS_BMAPI_PREALLOC, 0, imapp,
> -				&nimaps);
> 		error = xfs_bmapi_write(tp, ip, startoffset_fsb, allocatesize_fsb,
> +				flags, 0, imapp, &nimaps);
>  		if (error) {
>  			if (error != -ENOSR)
>  				goto error;
> diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
> index c477b33616304..67770830eb245 100644
> --- a/fs/xfs/xfs_bmap_util.h
> +++ b/fs/xfs/xfs_bmap_util.h
> @@ -55,8 +55,8 @@ int	xfs_bmap_last_extent(struct xfs_trans *tp, struct xfs_inode *ip,
>  			     int *is_empty);
>  
>  /* preallocation and hole punch interface */
> -int	xfs_alloc_file_space(struct xfs_inode *ip, xfs_off_t offset,
> -		xfs_off_t len);
> +int	xfs_alloc_file_space(struct xfs_inode *ip, uint32_t flags,
> +		xfs_off_t offset, xfs_off_t len);
>  int	xfs_free_file_space(struct xfs_inode *ip, xfs_off_t offset,
>  		xfs_off_t len, struct xfs_zone_alloc_ctx *ac);
>  int	xfs_collapse_file_space(struct xfs_inode *, xfs_off_t offset,
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index f96fbf5c54c99..b7e8cda62bb73 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1255,29 +1255,37 @@ xfs_falloc_insert_range(
>  static int
>  xfs_falloc_zero_range(
>  	struct file		*file,
> -	int			mode,
> +	int				mode,
>  	loff_t			offset,
>  	loff_t			len,
>  	struct xfs_zone_alloc_ctx *ac)
>  {
>  	struct inode		*inode = file_inode(file);
> +	struct xfs_inode	*ip = XFS_I(inode);
>  	unsigned int		blksize = i_blocksize(inode);
>  	loff_t			new_size = 0;
>  	int			error;
>  
> -	trace_xfs_zero_file_space(XFS_I(inode));
> +	trace_xfs_zero_file_space(ip);
>  
>  	error = xfs_falloc_newsize(file, mode, offset, len, &new_size);
>  	if (error)
>  		return error;
>  
> -	error = xfs_free_file_space(XFS_I(inode), offset, len, ac);
> +	error = xfs_free_file_space(ip, offset, len, ac);
>  	if (error)
>  		return error;
>  
>  	len = round_up(offset + len, blksize) - round_down(offset, blksize);
>  	offset = round_down(offset, blksize);
> -	error = xfs_alloc_file_space(XFS_I(inode), offset, len);
> +	if (mode & FALLOC_FL_WRITE_ZEROES) {
> +		if (!bdev_write_zeroes_unmap_sectors(xfs_inode_buftarg(ip)->bt_bdev))
> +			return -EOPNOTSUPP;
> +		xfs_alloc_file_space(ip, XFS_BMAPI_ZERO, offset, len);

Don't we need to check the return value of xfs_alloc_file_space?

--D

> +	} else {
> +		error = xfs_alloc_file_space(ip, XFS_BMAPI_PREALLOC,
> +				offset, len);
> +	}
>  	if (error)
>  		return error;
>  	return xfs_falloc_setsize(file, new_size);
> @@ -1302,7 +1310,8 @@ xfs_falloc_unshare_range(
>  	if (error)
>  		return error;
>  
> -	error = xfs_alloc_file_space(XFS_I(inode), offset, len);
> +	error = xfs_alloc_file_space(XFS_I(inode), XFS_BMAPI_PREALLOC,
> +			offset, len);
>  	if (error)
>  		return error;
>  	return xfs_falloc_setsize(file, new_size);
> @@ -1330,7 +1339,8 @@ xfs_falloc_allocate_range(
>  	if (error)
>  		return error;
>  
> -	error = xfs_alloc_file_space(XFS_I(inode), offset, len);
> +	error = xfs_alloc_file_space(XFS_I(inode), XFS_BMAPI_PREALLOC,
> +			offset, len);
>  	if (error)
>  		return error;
>  	return xfs_falloc_setsize(file, new_size);
> @@ -1340,7 +1350,7 @@ xfs_falloc_allocate_range(
>  		(FALLOC_FL_ALLOCATE_RANGE | FALLOC_FL_KEEP_SIZE |	\
>  		 FALLOC_FL_PUNCH_HOLE |	FALLOC_FL_COLLAPSE_RANGE |	\
>  		 FALLOC_FL_ZERO_RANGE |	FALLOC_FL_INSERT_RANGE |	\
> -		 FALLOC_FL_UNSHARE_RANGE)
> +		 FALLOC_FL_UNSHARE_RANGE | FALLOC_FL_WRITE_ZEROES)
>  
>  STATIC long
>  __xfs_file_fallocate(
> @@ -1383,6 +1393,7 @@ __xfs_file_fallocate(
>  	case FALLOC_FL_INSERT_RANGE:
>  		error = xfs_falloc_insert_range(file, offset, len);
>  		break;
> +	case FALLOC_FL_WRITE_ZEROES:
>  	case FALLOC_FL_ZERO_RANGE:
>  		error = xfs_falloc_zero_range(file, mode, offset, len, ac);
>  		break;
> -- 
> 2.51.0
>