Re: [PATCH 4/6] xfs: refactor __xfs_filemap_fault

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

On Wed, Jun 19, 2024 at 01:53:54PM +0200, Christoph Hellwig wrote:
> Split the write fault and DAX fault handling into separate helpers
> so that the main fault handler is easier to follow.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/xfs/xfs_file.c | 71 ++++++++++++++++++++++++++++++-----------------
>  1 file changed, 45 insertions(+), 26 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 8aab2f66fe016f..51e50afd935895 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1252,7 +1252,7 @@ xfs_file_llseek(
>  }
>  
>  static inline vm_fault_t
> -xfs_dax_fault(
> +xfs_dax_fault_locked(
>  	struct vm_fault		*vmf,
>  	unsigned int		order,
>  	bool			write_fault)
> @@ -1273,6 +1273,45 @@ xfs_dax_fault(
>  	return ret;
>  }
>  
> +static vm_fault_t
> +xfs_dax_fault(

Oh, hey, you /did/ split the dax handling into two helpers.

Would you mind renaming this xfs_dax_read_fault since this doesn't
handle write faults?

With that changed,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> +	struct vm_fault		*vmf,
> +	unsigned int		order)
> +{
> +	struct xfs_inode	*ip = XFS_I(file_inode(vmf->vma->vm_file));
> +	unsigned int		lock_mode;
> +	vm_fault_t		ret;
> +
> +	lock_mode = xfs_ilock_for_write_fault(ip);
> +	ret = xfs_dax_fault_locked(vmf, order, false);
> +	xfs_iunlock(ip, lock_mode);
> +
> +	return ret;
> +}
> +
> +static vm_fault_t
> +xfs_write_fault(
> +	struct vm_fault		*vmf,
> +	unsigned int		order)
> +{
> +	struct inode		*inode = file_inode(vmf->vma->vm_file);
> +	unsigned int		lock_mode;
> +	vm_fault_t		ret;
> +
> +	sb_start_pagefault(inode->i_sb);
> +	file_update_time(vmf->vma->vm_file);
> +
> +	lock_mode = xfs_ilock_for_write_fault(XFS_I(inode));
> +	if (IS_DAX(inode))
> +		ret = xfs_dax_fault_locked(vmf, order, true);
> +	else
> +		ret = iomap_page_mkwrite(vmf, &xfs_page_mkwrite_iomap_ops);
> +	xfs_iunlock(XFS_I(inode), lock_mode);
> +
> +	sb_end_pagefault(inode->i_sb);
> +	return ret;
> +}
> +
>  /*
>   * Locking for serialisation of IO during page faults. This results in a lock
>   * ordering of:
> @@ -1290,34 +1329,14 @@ __xfs_filemap_fault(
>  	bool			write_fault)
>  {
>  	struct inode		*inode = file_inode(vmf->vma->vm_file);
> -	struct xfs_inode	*ip = XFS_I(inode);
> -	vm_fault_t		ret;
> -	unsigned int		lock_mode = 0;
>  
> -	trace_xfs_filemap_fault(ip, order, write_fault);
> -
> -	if (write_fault) {
> -		sb_start_pagefault(inode->i_sb);
> -		file_update_time(vmf->vma->vm_file);
> -	}
> -
> -	if (IS_DAX(inode) || write_fault)
> -		lock_mode = xfs_ilock_for_write_fault(XFS_I(inode));
> -
> -	if (IS_DAX(inode)) {
> -		ret = xfs_dax_fault(vmf, order, write_fault);
> -	} else if (write_fault) {
> -		ret = iomap_page_mkwrite(vmf, &xfs_page_mkwrite_iomap_ops);
> -	} else {
> -		ret = filemap_fault(vmf);
> -	}
> -
> -	if (lock_mode)
> -		xfs_iunlock(XFS_I(inode), lock_mode);
> +	trace_xfs_filemap_fault(XFS_I(inode), order, write_fault);
>  
>  	if (write_fault)
> -		sb_end_pagefault(inode->i_sb);
> -	return ret;
> +		return xfs_write_fault(vmf, order);
> +	if (IS_DAX(inode))
> +		return xfs_dax_fault(vmf, order);
> +	return filemap_fault(vmf);
>  }
>  
>  static inline bool
> -- 
> 2.43.0
> 
>