smb: client: call ib_dma_unmap_sg if mr->sgt.nents is not 0

This seems to be the more reliable way to check if we need to
call ib_dma_unmap_sg().

Fixes: c739858 ("CIFS: SMBD: Implement RDMA memory registration")
Cc: Steve French <[email protected]>
Cc: Tom Talpey <[email protected]>
Cc: Long Li <[email protected]>
Cc: Namjae Jeon <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Stefan Metzmacher <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: metze-samba

fs/smb/client/smbdirect.c

@@ -2365,9 +2365,8 @@ 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->state == SMBDIRECT_MR_INVALIDATED)
-			ib_dma_unmap_sg(sc->ib.dev, mr->sgt.sgl,
-				mr->sgt.nents, mr->dir);
+		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);
@@ -2589,6 +2588,7 @@ struct smbdirect_mr_io *smbd_register_mr(struct smbd_connection *info,
 	ib_dma_unmap_sg(sc->ib.dev, mr->sgt.sgl, mr->sgt.nents, mr->dir);
 
 dma_map_error:
+	mr->sgt.nents = 0;
 	mr->state = SMBDIRECT_MR_ERROR;
 	if (atomic_dec_and_test(&sc->mr_io.used.count))
 		wake_up(&sc->mr_io.cleanup.wait_queue);
@@ -2651,8 +2651,12 @@ void smbd_deregister_mr(struct smbdirect_mr_io *mr)
 		 */
 		mr->state = SMBDIRECT_MR_INVALIDATED;
 
-	if (mr->state == SMBDIRECT_MR_INVALIDATED) {
+	if (mr->sgt.nents) {
 		ib_dma_unmap_sg(sc->ib.dev, mr->sgt.sgl, mr->sgt.nents, mr->dir);
+		mr->sgt.nents = 0;
+	}
+
+	if (mr->state == SMBDIRECT_MR_INVALIDATED) {
 		mr->state = SMBDIRECT_MR_READY;
 		if (atomic_inc_return(&sc->mr_io.ready.count) == 1)
 			wake_up(&sc->mr_io.ready.wait_queue);