On Wed, Apr 01, 2026 at 09:18:17PM +0200, Laurent Vivier wrote:
> Add a helper to set a range of bytes across an IO vector to a given
> value, similar to memset() but operating over scatter-gather buffers.
> It skips to the given offset and fills across iovec entries up to the
> requested length.
> 
> Signed-off-by: Laurent Vivier <lvivier@redhat.com>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  iov.c | 27 +++++++++++++++++++++++++++
>  iov.h |  2 ++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/iov.c b/iov.c
> index ae0743931d18..0188acdf5eba 100644
> --- a/iov.c
> +++ b/iov.c
> @@ -170,6 +170,33 @@ size_t iov_truncate(struct iovec *iov, size_t iov_cnt, size_t size)
>  	return i;
>  }
>  
> +/**
> + * iov_memset() - Set bytes of an IO vector to a given value
> + * @iov:	IO vector
> + * @iov_cnt:	Number of elements in @iov
> + * @offset:	Byte offset in the iovec at which to start
> + * @c:		Byte value to fill with
> + * @length:	Number of bytes to set
> + * 		Will write less than @length bytes if it runs out of space in
> + * 		the iov
> + */
> +/* cppcheck-suppress unusedFunction */
> +void iov_memset(const struct iovec *iov, size_t iov_cnt, size_t offset, int c,
> +		size_t length)
> +{
> +	size_t i;
> +
> +	i = iov_skip_bytes(iov, iov_cnt, offset, &offset);
> +
> +	for ( ; i < iov_cnt && length; i++) {
> +		size_t n = MIN(iov[i].iov_len - offset, length);
> +
> +		memset((char *)iov[i].iov_base + offset, c, n);
> +		offset = 0;
> +		length -= n;
> +	}
> +}
> +
>  /**
>   * iov_tail_prune() - Remove any unneeded buffers from an IOV tail
>   * @tail:	IO vector tail (modified)
> diff --git a/iov.h b/iov.h
> index b4e50b0fca5a..d295d05b3bab 100644
> --- a/iov.h
> +++ b/iov.h
> @@ -30,6 +30,8 @@ size_t iov_to_buf(const struct iovec *iov, size_t iov_cnt,
>  		  size_t offset, void *buf, size_t bytes);
>  size_t iov_size(const struct iovec *iov, size_t iov_cnt);
>  size_t iov_truncate(struct iovec *iov, size_t iov_cnt, size_t size);
> +void iov_memset(const struct iovec *iov, size_t iov_cnt, size_t offset, int c,
> +		size_t length);
>  
>  /*
>   * DOC: Theory of Operation, struct iov_tail
> -- 
> 2.53.0
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson