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.
Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
drivers/block/ublk_drv.c | 59 +++++++++++++++++++++++++-------
include/uapi/linux/ublk_cmd.h | 64 +++++++++++++++++++++++++++++++++++
2 files changed, 111 insertions(+), 12 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 87de455bec46..f2a57e633823 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 \
@@ -146,7 +147,16 @@ struct ublk_uring_cmd_pdu {
struct ublk_io {
/* userspace buffer address from io cmd */
- __u64 addr;
+ union {
+ __u64 addr;
+
+ /*
+ * Shared space with `addr`, see comment on
+ * `struct ublksrv_io_cmd` for the reason why it is safe to
+ * reuse '->addr' space
+ */
+ struct ublk_auto_buf_reg buf;
+ };
unsigned int flags;
int res;
@@ -631,7 +641,7 @@ 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)
@@ -1176,16 +1186,31 @@ static inline void __ublk_abort_rq(struct ublk_queue *ubq,
blk_mq_end_request(rq, BLK_STS_IOERR);
}
+static void ublk_auto_buf_reg_fallback(struct request *req, struct ublk_io *io,
+ unsigned int issue_flags)
+{
+ const struct ublk_queue *ubq = req->mq_hctx->driver_data;
+ struct ublksrv_io_desc *iod = ublk_get_iod(ubq, req->tag);
+ struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+
+ iod->op_flags |= UBLK_IO_F_NEED_REG_BUF;
+ refcount_set(&data->ref, 1);
+ ublk_complete_io_cmd(io, req, UBLK_IO_RES_OK, issue_flags);
+}
+
static bool ublk_auto_buf_reg(struct request *req, struct ublk_io *io,
unsigned int issue_flags)
{
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,
+ io->buf.index, issue_flags);
if (ret) {
- blk_mq_end_request(req, BLK_STS_IOERR);
+ if (io->buf.flags & UBLK_AUTO_BUF_REG_FALLBACK)
+ ublk_auto_buf_reg_fallback(req, io, issue_flags);
+ else
+ blk_mq_end_request(req, BLK_STS_IOERR);
return false;
}
/* one extra reference is dropped by ublk_io_release */
@@ -2028,7 +2053,7 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
*/
if (!buf_addr && !ublk_need_get_data(ubq))
goto out;
- } else if (buf_addr) {
+ } else if (buf_addr && !ublk_support_auto_buf_reg(ubq)) {
/* User copy requires addr to be unset */
ret = -EINVAL;
goto out;
@@ -2044,7 +2069,7 @@ static int ublk_fetch(struct io_uring_cmd *cmd, struct ublk_queue *ubq,
static void ublk_auto_buf_unreg(struct ublk_io *io, struct io_uring_cmd *cmd,
struct request *req, unsigned int issue_flags)
{
- WARN_ON_ONCE(io_buffer_unregister_bvec(cmd, 0, issue_flags));
+ WARN_ON_ONCE(io_buffer_unregister_bvec(cmd, io->buf.index, issue_flags));
io->flags &= ~UBLK_IO_FLAG_AUTO_BUF_REG;
}
@@ -2063,7 +2088,8 @@ static int ublk_commit_and_fetch(const struct ublk_queue *ubq,
if (!ub_cmd->addr && (!ublk_need_get_data(ubq) ||
req_op(req) == REQ_OP_READ))
return -EINVAL;
- } else if (req_op(req) != REQ_OP_ZONE_APPEND && ub_cmd->addr) {
+ } else if ((req_op(req) != REQ_OP_ZONE_APPEND &&
+ !ublk_support_auto_buf_reg(ubq)) && ub_cmd->addr) {
/*
* User copy requires addr to be unset when command is
* not zone append
@@ -2807,8 +2833,11 @@ 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;
}
@@ -2866,17 +2895,22 @@ 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;
/*
* 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
+ *
+ * UBLK_F_AUTO_BUF_REG can't be enabled for zoned because it need
+ * the space for getting ring_fd and buffer index.
*/
if (ublk_dev_is_zoned(ub) &&
(!IS_ENABLED(CONFIG_BLK_DEV_ZONED) || !(ub->dev_info.flags &
- (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY)))) {
+ (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY)) ||
+ (ub->dev_info.flags & UBLK_F_AUTO_BUF_REG))) {
ret = -EINVAL;
goto out_free_dev_number;
}
@@ -3393,6 +3427,7 @@ 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) > sizeof(__u64));
init_waitqueue_head(&ublk_idr_wq);
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index be5c6c6b16e0..a77b0cd7af48 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -219,6 +219,27 @@
*/
#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
+ *
+ * - pass buffer index from `ublksrv_io_cmd.buf.index`
+ *
+ * - pass flags from `ublksrv_io_cmd.buf.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.
+ *
+ * This feature isn't available for UBLK_F_ZONED
+ */
+#define UBLK_F_AUTO_BUF_REG (1ULL << 11)
+
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
@@ -305,6 +326,17 @@ struct ublksrv_ctrl_dev_info {
#define UBLK_IO_F_FUA (1U << 13)
#define UBLK_IO_F_NOUNMAP (1U << 15)
#define UBLK_IO_F_SWAP (1U << 16)
+/*
+ * For UBLK_F_AUTO_BUF_REG & UBLK_AUTO_BUF_REG_FALLBACK only.
+ *
+ * This flag is set if auto buffer register is failed & ublk server passes
+ * UBLK_AUTO_BUF_REG_FALLBACK, and ublk server need to register buffer
+ * manually for handling the delivered IO command if this flag is observed
+ *
+ * ublk server has to check this flag if UBLK_AUTO_BUF_REG_FALLBACK is
+ * passed in.
+ */
+#define UBLK_IO_F_NEED_REG_BUF (1U << 17)
/*
* io cmd is described by this structure, and stored in share memory, indexed
@@ -339,6 +371,30 @@ static inline __u32 ublksrv_get_flags(const struct ublksrv_io_desc *iod)
return iod->op_flags >> 8;
}
+/*
+ * If this flag is set, fallback by completing the uring_cmd and setting
+ * `UBLK_IO_F_NEED_REG_BUF` in case of auto-buf-register failure;
+ * otherwise the client ublk request is failed silently
+ *
+ * If ublk server passes this flag, it has to check if UBLK_IO_F_NEED_REG_BUF
+ * is set in `ublksrv_io_desc.op_flags`. If UBLK_IO_F_NEED_REG_BUF is set,
+ * ublk server needs to register io buffer manually for handling IO command.
+ */
+#define UBLK_AUTO_BUF_REG_FALLBACK (1 << 0)
+
+struct ublk_auto_buf_reg {
+ /* index for registering the delivered request buffer */
+ __u16 index;
+ __u8 flags;
+ __u8 _pad;
+
+ /*
+ * io_ring FD can be passed via the reserve field in future for
+ * supporting to register io buffer to external io_uring
+ */
+ __u32 reserved;
+};
+
/* issued to ublk driver via /dev/ublkcN */
struct ublksrv_io_cmd {
__u16 q_id;
@@ -363,6 +419,14 @@ struct ublksrv_io_cmd {
*/
__u64 addr;
__u64 zone_append_lba;
+
+ /*
+ * for AUTO_BUF_REG feature, F_ZONED can't be supported,
+ * meantime ->addr is available for zero copy because
+ * AUTO_BUF_REG is zero copy too & needn't user backed
+ * buffer.
+ */
+ struct ublk_auto_buf_reg auto_buf;
};
};
--
2.47.0
