[PATCH 17/26] cifs: Support ITER_BVECQ in smb_extract_iter_to_rdma()

[Stefan Metzmacher]

Hi David,

this conflicts with my patches in ksmbd-for-next
where we have this as smbdirect_map_sges_from_iter
and shared between client and server.

Can you rebase on ksmbd-for-next?

Thanks!
metze

Am 26.03.26 um 11:45 schrieb David Howells:
> Add support for ITER_BVECQ to smb_extract_iter_to_rdma().
> 
> Signed-off-by: David Howells <dhowells at redhat.com>
> cc: Paulo Alcantara <pc at manguebit.org>
> cc: Matthew Wilcox <willy at infradead.org>
> cc: Christoph Hellwig <hch at infradead.org>
> cc: Steve French <sfrench at samba.org>
> cc: Shyam Prasad N <sprasad at microsoft.com>
> cc: Tom Talpey <tom at talpey.com>
> cc: linux-cifs at vger.kernel.org
> cc: netfs at lists.linux.dev
> cc: linux-fsdevel at vger.kernel.org
> ---
>   fs/smb/client/smbdirect.c | 60 +++++++++++++++++++++++++++++++++++++++
>   1 file changed, 60 insertions(+)
> 
> diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c
> index c79304012b08..f8a6be83db98 100644
> --- a/fs/smb/client/smbdirect.c
> +++ b/fs/smb/client/smbdirect.c
> @@ -3298,6 +3298,63 @@ static ssize_t smb_extract_folioq_to_rdma(struct iov_iter *iter,
>   	return ret;
>   }
>   
> +/*
> + * Extract memory fragments from a BVECQ-class iterator and add them to an RDMA
> + * list.  The folios are not pinned.
> + */
> +static ssize_t smb_extract_bvecq_to_rdma(struct iov_iter *iter,
> +					 struct smb_extract_to_rdma *rdma,
> +					 ssize_t maxsize)
> +{
> +	const struct bvecq *bq = iter->bvecq;
> +	unsigned int slot = iter->bvecq_slot;
> +	ssize_t ret = 0;
> +	size_t offset = iter->iov_offset;
> +
> +	if (slot >= bq->nr_slots) {
> +		bq = bq->next;
> +		if (WARN_ON_ONCE(!bq))
> +			return -EIO;
> +		slot = 0;
> +	}
> +
> +	do {
> +		struct bio_vec *bv = &bq->bv[slot];
> +		struct page *page = bv->bv_page;
> +		size_t bsize = bv->bv_len;
> +
> +		if (offset < bsize) {
> +			size_t part = umin(maxsize, bsize - offset);
> +
> +			if (!smb_set_sge(rdma, page, bv->bv_offset + offset, part))
> +				return -EIO;
> +
> +			offset += part;
> +			ret += part;
> +			maxsize -= part;
> +		}
> +
> +		if (offset >= bsize) {
> +			offset = 0;
> +			slot++;
> +			if (slot >= bq->nr_slots) {
> +				if (!bq->next) {
> +					WARN_ON_ONCE(ret < iter->count);
> +					break;
> +				}
> +				bq = bq->next;
> +				slot = 0;
> +			}
> +		}
> +	} while (rdma->nr_sge < rdma->max_sge && maxsize > 0);
> +
> +	iter->bvecq = bq;
> +	iter->bvecq_slot = slot;
> +	iter->iov_offset = offset;
> +	iter->count -= ret;
> +	return ret;
> +}
> +
>   /*
>    * Extract page fragments from up to the given amount of the source iterator
>    * and build up an RDMA list that refers to all of those bits.  The RDMA list
> @@ -3325,6 +3382,9 @@ static ssize_t smb_extract_iter_to_rdma(struct iov_iter *iter, size_t len,
>   	case ITER_FOLIOQ:
>   		ret = smb_extract_folioq_to_rdma(iter, rdma, len);
>   		break;
> +	case ITER_BVECQ:
> +		ret = smb_extract_bvecq_to_rdma(iter, rdma, len);
> +		break;
>   	default:
>   		WARN_ON_ONCE(1);
>   		return -EIO;
>