Add UBLK_F_AUTO_BUF_REG for supporting to register buffer automatically
to local io_uring context with provided buffer index.
Add UAPI structure `struct ublk_auto_buf_reg` for holding user parameter
to register request buffer automatically, one 'flags' field is defined, and
there is still 32bit available for future extension, such as, adding one
io_ring FD field for registering buffer to external io_uring.
`struct ublk_auto_buf_reg` is populated from ublk uring_cmd's sqe->addr,
and all existing ublk commands are data-less, so it is just fine to reuse
sqe->addr for this purpose.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
drivers/block/ublk_drv.c | 54 ++++++++++++++++++++++++-----
include/uapi/linux/ublk_cmd.h | 64 +++++++++++++++++++++++++++++++++++
2 files changed, 109 insertions(+), 9 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index d0fd783c5404..0c8c18ea25bc 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -66,7 +66,8 @@
| UBLK_F_USER_COPY \
| UBLK_F_ZONED \
| UBLK_F_USER_RECOVERY_FAIL_IO \
- | UBLK_F_UPDATE_SIZE)
+ | UBLK_F_UPDATE_SIZE \
+ | UBLK_F_AUTO_BUF_REG)
#define UBLK_F_ALL_RECOVERY_FLAGS (UBLK_F_USER_RECOVERY \
| UBLK_F_USER_RECOVERY_REISSUE \
@@ -80,6 +81,9 @@
struct ublk_rq_data {
refcount_t ref;
+
+ /* for auto-unregister buffer in case of UBLK_F_AUTO_BUF_REG */
+ u16 buf_index;
};
struct ublk_uring_cmd_pdu {
@@ -101,6 +105,9 @@ struct ublk_uring_cmd_pdu {
* setup in ublk uring_cmd handler
*/
struct ublk_queue *ubq;
+
+ struct ublk_auto_buf_reg buf;
+
u16 tag;
};
@@ -630,7 +637,7 @@ static inline bool ublk_support_zero_copy(const struct ublk_queue *ubq)
static inline bool ublk_support_auto_buf_reg(const struct ublk_queue *ubq)
{
- return false;
+ return ubq->flags & UBLK_F_AUTO_BUF_REG;
}
static inline bool ublk_support_user_copy(const struct ublk_queue *ubq)
@@ -1178,17 +1185,20 @@ static inline void __ublk_abort_rq(struct ublk_queue *ubq,
static bool ublk_auto_buf_reg(struct request *req, struct ublk_io *io,
unsigned int issue_flags)
{
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(io->cmd);
struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
int ret;
- ret = io_buffer_register_bvec(io->cmd, req, ublk_io_release, 0,
- issue_flags);
+ ret = io_buffer_register_bvec(io->cmd, req, ublk_io_release,
+ pdu->buf.index, issue_flags);
if (ret) {
blk_mq_end_request(req, BLK_STS_IOERR);
return false;
}
/* one extra reference is dropped by ublk_io_release */
refcount_set(&data->ref, 2);
+ /* store buffer index in request payload */
+ data->buf_index = pdu->buf.index;
io->flags |= UBLK_IO_FLAG_AUTO_BUF_REG;
return true;
}
@@ -1952,6 +1962,18 @@ static inline void ublk_prep_cancel(struct io_uring_cmd *cmd,
io_uring_cmd_mark_cancelable(cmd, issue_flags);
}
+static inline bool ublk_set_auto_buf_reg(struct io_uring_cmd *cmd)
+{
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
+
+ pdu->buf = ublk_sqe_addr_to_auto_buf_reg(READ_ONCE(cmd->sqe->addr));
+
+ if (pdu->buf.reserved0 || pdu->buf.reserved1)
+ return false;
+
+ return true;
+}
+
static void ublk_io_release(void *priv)
{
struct request *rq = priv;
@@ -2041,9 +2063,13 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
return ret;
}
-static void ublk_auto_buf_unreg(struct ublk_io *io, unsigned int issue_flags)
+static void ublk_auto_buf_unreg(struct ublk_io *io, struct request *req,
+ unsigned int issue_flags)
{
- WARN_ON_ONCE(io_buffer_unregister_bvec(io->cmd, 0, issue_flags));
+ struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+
+ WARN_ON_ONCE(io_buffer_unregister_bvec(io->cmd, data->buf_index,
+ issue_flags));
io->flags &= ~UBLK_IO_FLAG_AUTO_BUF_REG;
}
@@ -2080,7 +2106,7 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
req->__sector = ub_cmd->zone_append_lba;
if (io->flags & UBLK_IO_FLAG_AUTO_BUF_REG)
- ublk_auto_buf_unreg(io, issue_flags);
+ ublk_auto_buf_unreg(io, req, issue_flags);
if (likely(!blk_should_fake_timeout(req->q)))
ublk_put_req_ref(ubq, req);
@@ -2182,6 +2208,11 @@ static int __ublk_ch_uring_cmd(struct io_uring_cmd *cmd,
default:
goto out;
}
+
+ /* we can't set data for auto_buf_reg until old data is consumed */
+ if (ublk_support_auto_buf_reg(ubq) && !ublk_set_auto_buf_reg(cmd))
+ return -EINVAL;
+
ublk_prep_cancel(cmd, issue_flags, ubq, tag);
return -EIOCBQUEUED;
@@ -2792,8 +2823,11 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
* For USER_COPY, we depends on userspace to fill request
* buffer by pwrite() to ublk char device, which can't be
* used for unprivileged device
+ *
+ * Same with zero copy or auto buffer register.
*/
- if (info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY))
+ if (info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY |
+ UBLK_F_AUTO_BUF_REG))
return -EINVAL;
}
@@ -2851,7 +2885,8 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
UBLK_F_URING_CMD_COMP_IN_TASK;
/* 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))
+ if (ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY |
+ UBLK_F_AUTO_BUF_REG))
ub->dev_info.flags &= ~UBLK_F_NEED_GET_DATA;
/*
@@ -3378,6 +3413,7 @@ static int __init ublk_init(void)
BUILD_BUG_ON((u64)UBLKSRV_IO_BUF_OFFSET +
UBLKSRV_IO_BUF_TOTAL_SIZE < UBLKSRV_IO_BUF_OFFSET);
+ BUILD_BUG_ON(sizeof(struct ublk_auto_buf_reg) != 8);
init_waitqueue_head(&ublk_idr_wq);
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index be5c6c6b16e0..663187cdfa52 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -219,6 +219,29 @@
*/
#define UBLK_F_UPDATE_SIZE (1ULL << 10)
+/*
+ * request buffer is registered automatically to uring_cmd's io_uring
+ * context before delivering this io command to ublk server, meantime
+ * it is un-registered automatically when completing this io command.
+ *
+ * For using this feature:
+ *
+ * - ublk server has to create sparse buffer table
+ *
+ * - ublk server passes auto buf register data via uring_cmd's sqe->addr,
+ * `struct ublk_auto_buf_reg` is populated from sqe->addr, please see
+ * the definition of ublk_sqe_addr_to_auto_buf_reg()
+ *
+ * - pass buffer index from `ublk_auto_buf_reg.index`
+ *
+ * - pass flags from `ublk_auto_buf_reg.flags` if needed
+ *
+ * This way avoids extra cost from two uring_cmd, but also simplifies backend
+ * implementation, such as, the dependency on IO_REGISTER_IO_BUF and
+ * IO_UNREGISTER_IO_BUF becomes not necessary.
+ */
+#define UBLK_F_AUTO_BUF_REG (1ULL << 11)
+
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
@@ -339,6 +362,47 @@ static inline __u32 ublksrv_get_flags(const struct ublksrv_io_desc *iod)
return iod->op_flags >> 8;
}
+struct ublk_auto_buf_reg {
+ /* index for registering the delivered request buffer */
+ __u16 index;
+ __u16 reserved0;
+
+ /*
+ * io_ring FD can be passed via the reserve field in future for
+ * supporting to register io buffer to external io_uring
+ */
+ __u32 reserved1;
+};
+
+/*
+ * For UBLK_F_AUTO_BUF_REG, auto buffer register data is carried via
+ * uring_cmd's sqe->addr:
+ *
+ * - bit0 ~ bit15: buffer index
+ * - bit24 ~ bit31: reserved0
+ * - bit32 ~ bit63: reserved1
+ */
+static inline struct ublk_auto_buf_reg ublk_sqe_addr_to_auto_buf_reg(
+ __u64 sqe_addr)
+{
+ struct ublk_auto_buf_reg reg = {
+ .index = sqe_addr & 0xffff,
+ .reserved0 = (sqe_addr >> 16) & 0xffff,
+ .reserved1 = sqe_addr >> 32,
+ };
+
+ return reg;
+}
+
+static inline __u64
+ublk_auto_buf_reg_to_sqe_addr(const struct ublk_auto_buf_reg *buf)
+{
+ __u64 addr = buf->index | (__u64)buf->reserved0 << 16 |
+ (__u64)buf->reserved1 << 32;
+
+ return addr;
+}
+
/* issued to ublk driver via /dev/ublkcN */
struct ublksrv_io_cmd {
__u16 q_id;
--
2.47.0
