tools/testing/selftests/ublk/file_backed.c

Source file repositories/reference/linux-study-clean/tools/testing/selftests/ublk/file_backed.c

File Facts

System
Linux kernel
Corpus path
tools/testing/selftests/ublk/file_backed.c
Extension
.c
Size
8104 bytes
Lines
283
Domain
Support Tooling And Documentation
Bucket
tools
Inferred role
Support Tooling And Documentation: implementation source
Status
source implementation candidate

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0

#include "kublk.h"

static enum io_uring_op ublk_to_uring_op(const struct ublksrv_io_desc *iod, int zc)
{
	unsigned ublk_op = ublksrv_get_op(iod);

	if (ublk_op == UBLK_IO_OP_READ)
		return zc ? IORING_OP_READ_FIXED : IORING_OP_READ;
	else if (ublk_op == UBLK_IO_OP_WRITE)
		return zc ? IORING_OP_WRITE_FIXED : IORING_OP_WRITE;
	ublk_assert(0);
}

static int loop_queue_flush_io(struct ublk_thread *t, struct ublk_queue *q,
			       const struct ublksrv_io_desc *iod, int tag)
{
	unsigned ublk_op = ublksrv_get_op(iod);
	struct io_uring_sqe *sqe[1];

	ublk_io_alloc_sqes(t, sqe, 1);
	io_uring_prep_fsync(sqe[0], ublk_get_registered_fd(q, 1) /*fds[1]*/, IORING_FSYNC_DATASYNC);
	io_uring_sqe_set_flags(sqe[0], IOSQE_FIXED_FILE);
	/* bit63 marks us as tgt io */
	sqe[0]->user_data = build_user_data(tag, ublk_op, 0, q->q_id, 1);
	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)
{
	unsigned ublk_op = ublksrv_get_op(iod);
	unsigned zc = ublk_queue_use_zc(q);
	unsigned auto_zc = ublk_queue_use_auto_zc(q);
	enum io_uring_op op = ublk_to_uring_op(iod, zc | auto_zc);
	struct ublk_io *io = ublk_get_io(q, tag);
	__u64 offset = iod->start_sector << 9;
	__u32 len = iod->nr_sectors << 9;
	struct io_uring_sqe *sqe[3];
	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 */
		io_uring_prep_rw(op, sqe[0], ublk_get_registered_fd(q, 2),
				 io->integrity_buf,
				 ublk_integrity_len(q, len),
				 ublk_integrity_len(q, offset));
		sqe[0]->flags = IOSQE_FIXED_FILE;
		/* tgt_data = 1 indicates integrity I/O */

Annotation

Implementation Notes