Fix smb_extract_iter_to_rdma() to use pre-decrement, not post-decrement, so
that it cleans up the correct slots.

Fixes: e5fbdde43017 ("cifs: Add a function to build an RDMA SGE list from an iterator")
Closes: https://sashiko.dev/#/patchset/20260326104544.509518-1-dhowells%40redhat.com
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Stefan Metzmacher <metze@samba.org>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Tom Talpey <tom@talpey.com>
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
---
 fs/smb/client/smbdirect.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/smb/client/smbdirect.c b/fs/smb/client/smbdirect.c
index 7d5f66bdbb30..4978755c035c 100644
--- a/fs/smb/client/smbdirect.c
+++ b/fs/smb/client/smbdirect.c
@@ -3394,7 +3394,7 @@ static ssize_t smb_extract_iter_to_rdma(struct iov_iter *iter, size_t len,
 
 	if (ret < 0) {
 		while (rdma->nr_sge > before) {
-			struct ib_sge *sge = &rdma->sge[rdma->nr_sge--];
+			struct ib_sge *sge = &rdma->sge[--rdma->nr_sge];
 
 			ib_dma_unmap_single(rdma->device, sge->addr, sge->length,
 					    rdma->direction);