Commit 53f427e7 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

ublk: support UBLK_AUTO_BUF_REG_FALLBACK 



For UBLK_F_AUTO_BUF_REG, buffer is registered to uring_cmd context
automatically with the provided buffer index. User may provide one wrong
buffer index, or the specified buffer is registered by application already.

Add UBLK_AUTO_BUF_REG_FALLBACK for supporting to auto buffer registering
fallback by completing the uring_cmd and telling ublk server the
register failure via UBLK_AUTO_BUF_REG_FALLBACK, then ublk server still
can register the buffer from userspace.

So we can provide reliable way for supporting auto buffer register.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250520045455.515691-5-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 99c1e4eb

drivers/block/ublk_drv.c

+16 −0
Original line number Diff line number Diff line
@@ -1182,6 +1182,16 @@ 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)

{

	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);

}



static bool ublk_auto_buf_reg(struct request *req, struct ublk_io *io,

			      unsigned int issue_flags)

{
@@ -1192,6 +1202,10 @@ static bool ublk_auto_buf_reg(struct request *req, struct ublk_io *io, 
	ret = io_buffer_register_bvec(io->cmd, req, ublk_io_release,

				      pdu->buf.index, issue_flags);

	if (ret) {

		if (pdu->buf.flags & UBLK_AUTO_BUF_REG_FALLBACK) {

			ublk_auto_buf_reg_fallback(req, io);

			return true;

		}

		blk_mq_end_request(req, BLK_STS_IOERR);

		return false;

	}
@@ -1971,6 +1985,8 @@ static inline int ublk_set_auto_buf_reg(struct io_uring_cmd *cmd) 
	if (pdu->buf.reserved0 || pdu->buf.reserved1)

		return -EINVAL;



	if (pdu->buf.flags & ~UBLK_AUTO_BUF_REG_F_MASK)

		return -EINVAL;

	return 0;

}

include/uapi/linux/ublk_cmd.h

+36 −3
Original line number Diff line number Diff line
@@ -236,9 +236,16 @@ 
 *

 * - all reserved fields in `ublk_auto_buf_reg` need to be zeroed

 *

 * - 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.

 *

 * If wrong data or flags are provided, both IO_FETCH_REQ and

 * IO_COMMIT_AND_FETCH_REQ are failed, for the latter, the ublk IO request

 * won't be completed until new IO_COMMIT_AND_FETCH_REQ command is issued

 * successfully

 */

#define UBLK_F_AUTO_BUF_REG 	(1ULL << 11)
@@ -328,6 +335,17 @@ 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
@@ -362,10 +380,23 @@ 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)

#define UBLK_AUTO_BUF_REG_F_MASK 	UBLK_AUTO_BUF_REG_FALLBACK



struct ublk_auto_buf_reg {

	/* index for registering the delivered request buffer */

	__u16  index;

	__u16   reserved0;

	__u8   flags;

	__u8   reserved0;



	/*

	 * io_ring FD can be passed via the reserve field in future for
@@ -379,6 +410,7 @@ struct ublk_auto_buf_reg { 
 * uring_cmd's sqe->addr:

 *

 * 	- bit0 ~ bit15: buffer index

 * 	- bit16 ~ bit23: flags

 * 	- bit24 ~ bit31: reserved0

 * 	- bit32 ~ bit63: reserved1

 */
@@ -387,7 +419,8 @@ static inline struct ublk_auto_buf_reg ublk_sqe_addr_to_auto_buf_reg( 
{

	struct ublk_auto_buf_reg reg = {

		.index = sqe_addr & 0xffff,

		.reserved0 = (sqe_addr >> 16) & 0xffff,

		.flags = (sqe_addr >> 16) & 0xff,

		.reserved0 = (sqe_addr >> 24) & 0xff,

		.reserved1 = sqe_addr >> 32,

	};
@@ -397,7 +430,7 @@ static inline struct ublk_auto_buf_reg ublk_sqe_addr_to_auto_buf_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 addr = buf->index | (__u64)buf->flags << 16 | (__u64)buf->reserved0 << 24 |

		(__u64)buf->reserved1 << 32;



	return addr;