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/*
 * device DAX engine
 *
 * IO engine that reads/writes from files by doing memcpy to/from
 * a memory mapped region of DAX enabled device.
 *
 * Copyright (C) 2016 Intel Corp
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License,
 * version 2 as published by the Free Software Foundation..
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 */

/*
 * device dax engine
 * IO engine that access a DAX device directly for read and write data
 *
 * To use:
 *   ioengine=dev-dax
 *
 *   Other relevant settings:
 *     iodepth=1
 *     direct=0	   REQUIRED
 *     filename=/dev/daxN.N
 *     bs=2m
 *
 *     direct should be left to 0. Using dev-dax implies that memory access
 *     is direct. However, dev-dax does not support O_DIRECT flag by design
 *     since it is not necessary.
 *
 *     bs should adhere to the device dax alignment at minimally.
 *
 * libpmem.so
 *   By default, the dev-dax engine will let the system find the libpmem.so
 *   that it uses. You can use an alternative libpmem by setting the
 *   FIO_PMEM_LIB environment variable to the full path to the desired
 *   libpmem.so.
 */

#include <stdio.h>
#include <limits.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <libgen.h>
#include <libpmem.h>

#include "../fio.h"
#include "../verify.h"

/*
 * Limits us to 1GiB of mapped files in total to model after
 * mmap engine behavior
 */
#define MMAP_TOTAL_SZ	(1 * 1024 * 1024 * 1024UL)

struct fio_devdax_data {
	void *devdax_ptr;
	size_t devdax_sz;
	off_t devdax_off;
};

static int fio_devdax_file(struct thread_data *td, struct fio_file *f,
			   size_t length, off_t off)
{
	struct fio_devdax_data *fdd = FILE_ENG_DATA(f);
	int flags = 0;

	if (td_rw(td))
		flags = PROT_READ | PROT_WRITE;
	else if (td_write(td)) {
		flags = PROT_WRITE;

		if (td->o.verify != VERIFY_NONE)
			flags |= PROT_READ;
	} else
		flags = PROT_READ;

	fdd->devdax_ptr = mmap(NULL, length, flags, MAP_SHARED, f->fd, off);
	if (fdd->devdax_ptr == MAP_FAILED) {
		fdd->devdax_ptr = NULL;
		td_verror(td, errno, "mmap");
	}

	if (td->error && fdd->devdax_ptr)
		munmap(fdd->devdax_ptr, length);

	return td->error;
}

/*
 * Just mmap an appropriate portion, we cannot mmap the full extent
 */
static int fio_devdax_prep_limited(struct thread_data *td, struct io_u *io_u)
{
	struct fio_file *f = io_u->file;
	struct fio_devdax_data *fdd = FILE_ENG_DATA(f);

	if (io_u->buflen > f->real_file_size) {
		log_err("dev-dax: bs too big for dev-dax engine\n");
		return EIO;
	}

	fdd->devdax_sz = min(MMAP_TOTAL_SZ, f->real_file_size);
	if (fdd->devdax_sz > f->io_size)
		fdd->devdax_sz = f->io_size;

	fdd->devdax_off = io_u->offset;

	return fio_devdax_file(td, f, fdd->devdax_sz, fdd->devdax_off);
}

/*
 * Attempt to mmap the entire file
 */
static int fio_devdax_prep_full(struct thread_data *td, struct io_u *io_u)
{
	struct fio_file *f = io_u->file;
	struct fio_devdax_data *fdd = FILE_ENG_DATA(f);
	int ret;

	if (fio_file_partial_mmap(f))
		return EINVAL;

	if (io_u->offset != (size_t) io_u->offset ||
	    f->io_size != (size_t) f->io_size) {
		fio_file_set_partial_mmap(f);
		return EINVAL;
	}

	fdd->devdax_sz = f->io_size;
	fdd->devdax_off = 0;

	ret = fio_devdax_file(td, f, fdd->devdax_sz, fdd->devdax_off);
	if (ret)
		fio_file_set_partial_mmap(f);

	return ret;
}

static int fio_devdax_prep(struct thread_data *td, struct io_u *io_u)
{
	struct fio_file *f = io_u->file;
	struct fio_devdax_data *fdd = FILE_ENG_DATA(f);
	int ret;

	/*
	 * It fits within existing mapping, use it
	 */
	if (io_u->offset >= fdd->devdax_off &&
	    io_u->offset + io_u->buflen <= fdd->devdax_off + fdd->devdax_sz)
		goto done;

	/*
	 * unmap any existing mapping
	 */
	if (fdd->devdax_ptr) {
		if (munmap(fdd->devdax_ptr, fdd->devdax_sz) < 0)
			return errno;
		fdd->devdax_ptr = NULL;
	}

	if (fio_devdax_prep_full(td, io_u)) {
		td_clear_error(td);
		ret = fio_devdax_prep_limited(td, io_u);
		if (ret)
			return ret;
	}

done:
	io_u->mmap_data = fdd->devdax_ptr + io_u->offset - fdd->devdax_off -
				f->file_offset;
	return 0;
}

static enum fio_q_status fio_devdax_queue(struct thread_data *td,
					  struct io_u *io_u)
{
	fio_ro_check(td, io_u);
	io_u->error = 0;

	switch (io_u->ddir) {
	case DDIR_READ:
		memcpy(io_u->xfer_buf, io_u->mmap_data, io_u->xfer_buflen);
		break;
	case DDIR_WRITE:
		pmem_memcpy_persist(io_u->mmap_data, io_u->xfer_buf,
				    io_u->xfer_buflen);
		break;
	case DDIR_SYNC:
	case DDIR_DATASYNC:
	case DDIR_SYNC_FILE_RANGE:
		break;
	default:
		io_u->error = EINVAL;
		break;
	}

	return FIO_Q_COMPLETED;
}

static int fio_devdax_init(struct thread_data *td)
{
	struct thread_options *o = &td->o;

	if ((o->rw_min_bs & page_mask) &&
	    (o->fsync_blocks || o->fdatasync_blocks)) {
		log_err("dev-dax: mmap options dictate a minimum block size of %llu bytes\n",
			(unsigned long long) page_size);
		return 1;
	}

	return 0;
}

static int fio_devdax_open_file(struct thread_data *td, struct fio_file *f)
{
	struct fio_devdax_data *fdd;
	int ret;

	ret = generic_open_file(td, f);
	if (ret)
		return ret;

	fdd = calloc(1, sizeof(*fdd));
	if (!fdd) {
		int fio_unused __ret;
		__ret = generic_close_file(td, f);
		return 1;
	}

	FILE_SET_ENG_DATA(f, fdd);

	return 0;
}

static int fio_devdax_close_file(struct thread_data *td, struct fio_file *f)
{
	struct fio_devdax_data *fdd = FILE_ENG_DATA(f);

	FILE_SET_ENG_DATA(f, NULL);
	free(fdd);
	fio_file_clear_partial_mmap(f);

	return generic_close_file(td, f);
}

static int
fio_devdax_get_file_size(struct thread_data *td, struct fio_file *f)
{
	char spath[PATH_MAX];
	char npath[PATH_MAX];
	char *rpath, *basename;
	FILE *sfile;
	uint64_t size;
	struct stat st;
	int rc;

	if (fio_file_size_known(f))
		return 0;

	if (f->filetype != FIO_TYPE_CHAR)
		return -EINVAL;

	rc = stat(f->file_name, &st);
	if (rc < 0) {
		log_err("%s: failed to stat file %s (%s)\n",
			td->o.name, f->file_name, strerror(errno));
		return -errno;
	}

	snprintf(spath, PATH_MAX, "/sys/dev/char/%d:%d/subsystem",
		 major(st.st_rdev), minor(st.st_rdev));

	rpath = realpath(spath, npath);
	if (!rpath) {
		log_err("%s: realpath on %s failed (%s)\n",
			td->o.name, spath, strerror(errno));
		return -errno;
	}

	/* check if DAX device */
	basename = strrchr(rpath, '/');
	if (!basename || strcmp("dax", basename+1)) {
		log_err("%s: %s not a DAX device!\n",
			td->o.name, f->file_name);
	}

	snprintf(spath, PATH_MAX, "/sys/dev/char/%d:%d/size",
		 major(st.st_rdev), minor(st.st_rdev));

	sfile = fopen(spath, "r");
	if (!sfile) {
		log_err("%s: fopen on %s failed (%s)\n",
			td->o.name, spath, strerror(errno));
		return 1;
	}

	rc = fscanf(sfile, "%lu", &size);
	if (rc < 0) {
		log_err("%s: fscanf on %s failed (%s)\n",
			td->o.name, spath, strerror(errno));
		fclose(sfile);
		return 1;
	}

	f->real_file_size = size;

	fclose(sfile);

	if (f->file_offset > f->real_file_size) {
		log_err("%s: offset extends end (%llu > %llu)\n", td->o.name,
					(unsigned long long) f->file_offset,
					(unsigned long long) f->real_file_size);
		return 1;
	}

	fio_file_set_size_known(f);
	return 0;
}

FIO_STATIC struct ioengine_ops ioengine = {
	.name		= "dev-dax",
	.version	= FIO_IOOPS_VERSION,
	.init		= fio_devdax_init,
	.prep		= fio_devdax_prep,
	.queue		= fio_devdax_queue,
	.open_file	= fio_devdax_open_file,
	.close_file	= fio_devdax_close_file,
	.get_file_size	= fio_devdax_get_file_size,
	.flags		= FIO_SYNCIO | FIO_DISKLESSIO | FIO_NOEXTEND | FIO_NODISKUTIL,
};

static void fio_init fio_devdax_register(void)
{
	register_ioengine(&ioengine);
}

static void fio_exit fio_devdax_unregister(void)
{
	unregister_ioengine(&ioengine);
}