Commit ec20aa44 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

selftests/ublk: add UBLK_F_SHMEM_ZC support for loop target 



Add loop_queue_shmem_zc_io() which handles I/O requests marked with
UBLK_IO_F_SHMEM_ZC. When the kernel sets this flag, the request data
lives in a registered shared memory buffer — decode index + offset
from iod->addr and use the server's mmap as the I/O buffer.

The dispatch check in loop_queue_tgt_rw_io() routes SHMEM_ZC requests
to this new function, bypassing the normal buffer registration path.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://patch.msgid.link/20260331153207.3635125-7-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 166b476b

tools/testing/selftests/ublk/file_backed.c

+38 −0
Original line number Diff line number Diff line
@@ -27,6 +27,40 @@ static int loop_queue_flush_io(struct ublk_thread *t, struct ublk_queue *q, 
	return 1;

}



/*

 * Shared memory zero-copy I/O: when UBLK_IO_F_SHMEM_ZC is set, the

 * request's data lives in a registered shared memory buffer. Decode

 * index + offset from iod->addr and use the server's mmap of that

 * buffer as the I/O buffer for the backing file.

 */

static int loop_queue_shmem_zc_io(struct ublk_thread *t, struct ublk_queue *q,

				  const struct ublksrv_io_desc *iod, int tag)

{

	unsigned ublk_op = ublksrv_get_op(iod);

	enum io_uring_op op = ublk_to_uring_op(iod, 0);

	__u64 file_offset = iod->start_sector << 9;

	__u32 len = iod->nr_sectors << 9;

	__u32 shmem_idx = ublk_shmem_zc_index(iod->addr);

	__u32 shmem_off = ublk_shmem_zc_offset(iod->addr);

	struct io_uring_sqe *sqe[1];

	void *addr;



	if (shmem_idx >= UBLK_BUF_MAX || !shmem_table[shmem_idx].mmap_base)

		return -EINVAL;



	addr = shmem_table[shmem_idx].mmap_base + shmem_off;



	ublk_io_alloc_sqes(t, sqe, 1);

	if (!sqe[0])

		return -ENOMEM;



	io_uring_prep_rw(op, sqe[0], ublk_get_registered_fd(q, 1),

			 addr, len, file_offset);

	io_uring_sqe_set_flags(sqe[0], IOSQE_FIXED_FILE);

	sqe[0]->user_data = build_user_data(tag, ublk_op, 0, q->q_id, 1);

	return 1;

}



static int loop_queue_tgt_rw_io(struct ublk_thread *t, struct ublk_queue *q,

				const struct ublksrv_io_desc *iod, int tag)

{
@@ -41,6 +75,10 @@ static int loop_queue_tgt_rw_io(struct ublk_thread *t, struct ublk_queue *q, 
	void *addr = io->buf_addr;

	unsigned short buf_index = ublk_io_buf_idx(t, q, tag);



	/* shared memory zero-copy path */

	if (iod->op_flags & UBLK_IO_F_SHMEM_ZC)

		return loop_queue_shmem_zc_io(t, q, iod, tag);



	if (iod->op_flags & UBLK_IO_F_INTEGRITY) {

		ublk_io_alloc_sqes(t, sqe, 1);

		/* Use second backing file for integrity data */