ublk: decouple zero copy from user copy

UBLK_F_USER_COPY and UBLK_F_SUPPORT_ZERO_COPY are two different
features, and shouldn't be coupled together.

Commit 1f6540e2aabb ("ublk: zc register/unregister bvec") enables
user copy automatically in case of UBLK_F_SUPPORT_ZERO_COPY, this way
isn't correct.

So decouple zero copy from user copy, and use independent helper to
check each one.

Fixes: 1f6540e2aabb ("ublk: zc register/unregister bvec")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250429022941.1718671-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 40f971a66d3eb2dbf90bc1e87e6b63a5bd4144c5..0a3a3c64316d7e32f1a130ab2b19b999194796a0 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -205,11 +205,6 @@ static inline struct request *__ublk_check_and_get_req(struct ublk_device *ub,
 static inline unsigned int ublk_req_build_flags(struct request *req);
 static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq,
                                                   int tag);
-static inline bool ublk_dev_is_user_copy(const struct ublk_device *ub)
-{
-       return ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY);
-}
-
 static inline bool ublk_dev_is_zoned(const struct ublk_device *ub)
 {
        return ub->dev_info.flags & UBLK_F_ZONED;
@@ -609,14 +604,19 @@ static void ublk_apply_params(struct ublk_device *ub)
                ublk_dev_param_zoned_apply(ub);
 }
 
+static inline bool ublk_support_zero_copy(const struct ublk_queue *ubq)
+{
+       return ubq->flags & UBLK_F_SUPPORT_ZERO_COPY;
+}
+
 static inline bool ublk_support_user_copy(const struct ublk_queue *ubq)
 {
-       return ubq->flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY);
+       return ubq->flags & UBLK_F_USER_COPY;
 }
 
 static inline bool ublk_need_map_io(const struct ublk_queue *ubq)
 {
-       return !ublk_support_user_copy(ubq);
+       return !ublk_support_user_copy(ubq) && !ublk_support_zero_copy(ubq);
 }
 
 static inline bool ublk_need_req_ref(const struct ublk_queue *ubq)
@@ -624,8 +624,11 @@ static inline bool ublk_need_req_ref(const struct ublk_queue *ubq)
        /*
         * read()/write() is involved in user copy, so request reference
         * has to be grabbed
+        *
+        * for zero copy, request buffer need to be registered to io_uring
+        * buffer table, so reference is needed
         */
-       return ublk_support_user_copy(ubq);
+       return ublk_support_user_copy(ubq) || ublk_support_zero_copy(ubq);
 }
 
 static inline void ublk_init_req_ref(const struct ublk_queue *ubq,
@@ -2245,6 +2248,9 @@ static struct request *ublk_check_and_get_req(struct kiocb *iocb,
        if (!ubq)
                return ERR_PTR(-EINVAL);
 
+       if (!ublk_support_user_copy(ubq))
+               return ERR_PTR(-EACCES);
+
        if (tag >= ubq->q_depth)
                return ERR_PTR(-EINVAL);
 
@@ -2783,13 +2789,18 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
        ub->dev_info.flags |= UBLK_F_CMD_IOCTL_ENCODE |
                UBLK_F_URING_CMD_COMP_IN_TASK;
 
-       /* GET_DATA isn't needed any more with USER_COPY */
-       if (ublk_dev_is_user_copy(ub))
+       /* GET_DATA isn't needed any more with USER_COPY or ZERO COPY */
+       if (ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY))
                ub->dev_info.flags &= ~UBLK_F_NEED_GET_DATA;
 
-       /* Zoned storage support requires user copy feature */
+       /*
+        * Zoned storage support requires reuse `ublksrv_io_cmd->addr` for
+        * returning write_append_lba, which is only allowed in case of
+        * user copy or zero copy
+        */
        if (ublk_dev_is_zoned(ub) &&
-           (!IS_ENABLED(CONFIG_BLK_DEV_ZONED) || !ublk_dev_is_user_copy(ub))) {
+           (!IS_ENABLED(CONFIG_BLK_DEV_ZONED) || !(ub->dev_info.flags &
+            (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY)))) {
                ret = -EINVAL;
                goto out_free_dev_number;
        }