From 62fe99cef94a5900cac3bf15fd03ee8baad1a99c Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Fri, 19 May 2023 14:50:29 +0800 Subject: ublk: add read()/write() support for ublk char device Support pread()/pwrite() on ublk char device for reading/writing request io buffer, so data copy between io request buffer and userspace buffer can be moved to ublk server from ublk driver. Then UBLK_F_NEED_GET_DATA becomes not necessary, so ublk server can allocate buffer without one extra round uring command communication for userspace to provide buffer. IO buffer can be located by iocb->ki_pos which encodes buffer offset, io tag and queue id info, and type of iocb->ki_pos is u64, so it is big enough for holding reasonable queue depth, nr_queues and max io buffer size. Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20230519065030.351216-7-ming.lei@redhat.com Signed-off-by: Jens Axboe --- include/uapi/linux/ublk_cmd.h | 22 +++++++++++++++++++++- 1 file changed, 21 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h index 640bf687b94a..c0c1632c671e 100644 --- a/include/uapi/linux/ublk_cmd.h +++ b/include/uapi/linux/ublk_cmd.h @@ -93,9 +93,29 @@ #define UBLKSRV_CMD_BUF_OFFSET 0 #define UBLKSRV_IO_BUF_OFFSET 0x80000000 -/* tag bit is 12bit, so at most 4096 IOs for each queue */ +/* tag bit is 16bit, so far limit at most 4096 IOs for each queue */ #define UBLK_MAX_QUEUE_DEPTH 4096 +/* single IO buffer max size is 32MB */ +#define UBLK_IO_BUF_OFF 0 +#define UBLK_IO_BUF_BITS 25 +#define UBLK_IO_BUF_BITS_MASK ((1ULL << UBLK_IO_BUF_BITS) - 1) + +/* so at most 64K IOs for each queue */ +#define UBLK_TAG_OFF UBLK_IO_BUF_BITS +#define UBLK_TAG_BITS 16 +#define UBLK_TAG_BITS_MASK ((1ULL << UBLK_TAG_BITS) - 1) + +/* max 4096 queues */ +#define UBLK_QID_OFF (UBLK_TAG_OFF + UBLK_TAG_BITS) +#define UBLK_QID_BITS 12 +#define UBLK_QID_BITS_MASK ((1ULL << UBLK_QID_BITS) - 1) + +#define UBLK_MAX_NR_QUEUES (1U << UBLK_QID_BITS) + +#define UBLKSRV_IO_BUF_TOTAL_BITS (UBLK_QID_OFF + UBLK_QID_BITS) +#define UBLKSRV_IO_BUF_TOTAL_SIZE (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS) + /* * zero copy requires 4k block size, and can remap ublk driver's io * request into ublksrv's vm space -- cgit v1.3.1