Re: [PATCH 1/2] iomap: don't bother unsharing delalloc extents

[Brian Foster <bfoster@redhat.com>]

On Wed, Oct 02, 2024 at 08:00:40AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
> 
> If unshare encounters a delalloc reservation in the srcmap, that means
> that the file range isn't shared because delalloc reservations cannot be
> reflinked.  Therefore, don't try to unshare them.
> 
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
>  fs/iomap/buffered-io.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 11ea747228aee..c1c559e0cc07c 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1321,7 +1321,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
>  		return length;
>  
>  	/*
> -	 * Don't bother with holes or unwritten extents.
> +	 * Don't bother with 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
> @@ -1330,6 +1330,7 @@ static loff_t iomap_unshare_iter(struct iomap_iter *iter)
>  	 * fork for XFS.
>  	 */
>  	if (iter->srcmap.type == IOMAP_HOLE ||
> +	    iter->srcmap.type == IOMAP_DELALLOC ||
>  	    iter->srcmap.type == IOMAP_UNWRITTEN)
>  		return length;
>  
> 

IIUC in the case of shared blocks srcmap always refers to the data fork
(so delalloc in the COW fork is not an issue). If so:

Reviewed-by: Brian Foster <bfoster@redhat.com>