Re: [PATCH] iomap: turn iomap_want_unshare_iter into an inline function

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

On Tue, Oct 15, 2024 at 06:13:50AM +0200, Christoph Hellwig wrote:
> iomap_want_unshare_iter currently sits in fs/iomap/buffered-io.c, which
> depends on CONFIG_BLOCK.  It is also in used in fs/dax.c whіch has no
> such dependency.  Given that it is a trivial check turn it into an inline
> in include/linux/iomap.h to fix the DAX && !BLOCK build.
> 
> Fixes: 6ef6a0e821d3 ("iomap: share iomap_unshare_iter predicate code with fsdax")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Heh, whoops.  I forgot (a) that DAX && !BLOCK is a thing; and that
FS_DAX != DAX and was puzzling over this report yesterday.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/iomap/buffered-io.c | 17 -----------------
>  include/linux/iomap.h  | 19 +++++++++++++++++++
>  2 files changed, 19 insertions(+), 17 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 604f786be4bc54..ef0b68bccbb612 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1270,23 +1270,6 @@ void iomap_write_delalloc_release(struct inode *inode, loff_t start_byte,
>  }
>  EXPORT_SYMBOL_GPL(iomap_write_delalloc_release);
>  
> -bool iomap_want_unshare_iter(const struct iomap_iter *iter)
> -{
> -	/*
> -	 * Don't bother with blocks that are not shared to start with; or
> -	 * mappings that cannot be shared, such as inline data, delalloc
> -	 * reservations, holes or unwritten extents.
> -	 *
> -	 * Note that we use srcmap directly instead of iomap_iter_srcmap as
> -	 * unsharing requires providing a separate source map, and the presence
> -	 * of one is a good indicator that unsharing is needed, unlike
> -	 * IOMAP_F_SHARED which can be set for any data that goes into the COW
> -	 * fork for XFS.
> -	 */
> -	return (iter->iomap.flags & IOMAP_F_SHARED) &&
> -		iter->srcmap.type == IOMAP_MAPPED;
> -}
> -
>  static loff_t iomap_unshare_iter(struct iomap_iter *iter)
>  {
>  	struct iomap *iomap = &iter->iomap;
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index e04c060e8fe185..664c5f2f0aaa2d 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -270,6 +270,25 @@ static inline loff_t iomap_last_written_block(struct inode *inode, loff_t pos,
>  	return round_up(pos + written, i_blocksize(inode));
>  }
>  
> +/*
> + * Check if the range needs to be unshared for a FALLOC_FL_UNSHARE_RANGE
> + * operation.
> + *
> + * Don't bother with blocks that are not shared to start with; or mappings that
> + * cannot be shared, such as inline data, delalloc reservations, holes or
> + * unwritten extents.
> + *
> + * Note that we use srcmap directly instead of iomap_iter_srcmap as unsharing
> + * requires providing a separate source map, and the presence of one is a good
> + * indicator that unsharing is needed, unlike IOMAP_F_SHARED which can be set
> + * for any data that goes into the COW fork for XFS.
> + */
> +static inline bool iomap_want_unshare_iter(const struct iomap_iter *iter)
> +{
> +	return (iter->iomap.flags & IOMAP_F_SHARED) &&
> +		iter->srcmap.type == IOMAP_MAPPED;
> +}
> +
>  ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from,
>  		const struct iomap_ops *ops, void *private);
>  int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops);
> -- 
> 2.45.2
> 
>