smb: client: let destroy_mr_list() call ib_dereg_mr() before ib_dma_unmap_sg()

This is more consistent as we call ib_dma_unmap_sg() only
when the memory is no longer registered.

This is the same pattern as calling ib_dma_unmap_sg() after
IB_WR_LOCAL_INV.

Fixes: c739858 ("CIFS: SMBD: Implement RDMA memory registration")
Cc: Steve French <smfrench@gmail.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Long Li <longli@microsoft.com>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: linux-cifs@vger.kernel.org
Cc: samba-technical@lists.samba.org
Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: metze-samba

fs/smb/client/smbdirect.c

@@ -2365,9 +2365,10 @@ static void destroy_mr_list(struct smbdirect_socket *sc)
 	spin_unlock_irqrestore(&sc->mr_io.all.lock, flags);
 
 	list_for_each_entry_safe(mr, tmp, &all_list, list) {
+		if (mr->mr)
+			ib_dereg_mr(mr->mr);
 		if (mr->sgt.nents)
 			ib_dma_unmap_sg(sc->ib.dev, mr->sgt.sgl, mr->sgt.nents, mr->dir);
-		ib_dereg_mr(mr->mr);
 		kfree(mr->sgt.sgl);
 		list_del(&mr->list);
 		kfree(mr);