splice.c revision b5af82930ccfd7dda6a1b11794efb452eb76d8dc 
1/*
2 * splice io engine
3 *
4 */
5#include <stdio.h>
6#include <stdlib.h>
7#include <unistd.h>
8#include <errno.h>
9#include <assert.h>
10#include <sys/poll.h>
11
12#include "../fio.h"
13#include "../os.h"
14
15#ifdef FIO_HAVE_SPLICE
16
17struct spliceio_data {
18	int pipe[2];
19};
20
21/*
22 * For splice reading, we unfortunately cannot (yet) vmsplice the other way.
23 * So just splice the data from the file into the pipe, and use regular
24 * read to fill the buffer. Doesn't make a lot of sense, but...
25 */
26static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
27{
28	struct spliceio_data *sd = td->io_ops->data;
29	struct fio_file *f = io_u->file;
30	int ret, ret2, buflen;
31	off_t offset;
32	void *p;
33
34	offset = io_u->offset;
35	buflen = io_u->xfer_buflen;
36	p = io_u->xfer_buf;
37	while (buflen) {
38		int this_len = buflen;
39
40		if (this_len > SPLICE_DEF_SIZE)
41			this_len = SPLICE_DEF_SIZE;
42
43		ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len, SPLICE_F_MORE);
44		if (ret < 0) {
45			if (errno == ENODATA || errno == EAGAIN)
46				continue;
47
48			return errno;
49		}
50
51		buflen -= ret;
52
53		while (ret) {
54			ret2 = read(sd->pipe[0], p, ret);
55			if (ret2 < 0)
56				return errno;
57
58			ret -= ret2;
59			p += ret2;
60		}
61	}
62
63	return io_u->xfer_buflen;
64}
65
66/*
67 * For splice writing, we can vmsplice our data buffer directly into a
68 * pipe and then splice that to a file.
69 */
70static int fio_splice_write(struct thread_data *td, struct io_u *io_u)
71{
72	struct spliceio_data *sd = td->io_ops->data;
73	struct iovec iov[1] = {
74		{
75			.iov_base = io_u->xfer_buf,
76			.iov_len = io_u->xfer_buflen,
77		}
78	};
79	struct pollfd pfd = { .fd = sd->pipe[1], .events = POLLOUT, };
80	struct fio_file *f = io_u->file;
81	off_t off = io_u->offset;
82	int ret, ret2;
83
84	while (iov[0].iov_len) {
85		if (poll(&pfd, 1, -1) < 0)
86			return errno;
87
88		ret = vmsplice(sd->pipe[1], iov, 1, SPLICE_F_NONBLOCK);
89		if (ret < 0)
90			return errno;
91
92		iov[0].iov_len -= ret;
93		iov[0].iov_base += ret;
94
95		while (ret) {
96			ret2 = splice(sd->pipe[0], NULL, f->fd, &off, ret, 0);
97			if (ret2 < 0)
98				return errno;
99
100			ret -= ret2;
101		}
102	}
103
104	return io_u->xfer_buflen;
105}
106
107static int fio_spliceio_queue(struct thread_data *td, struct io_u *io_u)
108{
109	int ret;
110
111	if (io_u->ddir == DDIR_READ)
112		ret = fio_splice_read(td, io_u);
113	else if (io_u->ddir == DDIR_WRITE)
114		ret = fio_splice_write(td, io_u);
115	else
116		ret = fsync(io_u->file->fd);
117
118	if (ret != (int) io_u->xfer_buflen) {
119		if (ret >= 0) {
120			io_u->resid = io_u->xfer_buflen - ret;
121			io_u->error = 0;
122			return FIO_Q_COMPLETED;
123		} else
124			io_u->error = errno;
125	}
126
127	if (io_u->error)
128		td_verror(td, io_u->error, "xfer");
129
130	return FIO_Q_COMPLETED;
131}
132
133static void fio_spliceio_cleanup(struct thread_data *td)
134{
135	struct spliceio_data *sd = td->io_ops->data;
136
137	if (sd) {
138		close(sd->pipe[0]);
139		close(sd->pipe[1]);
140		free(sd);
141		td->io_ops->data = NULL;
142	}
143}
144
145static int fio_spliceio_init(struct thread_data *td)
146{
147	struct spliceio_data *sd = malloc(sizeof(*sd));
148
149	if (pipe(sd->pipe) < 0) {
150		td_verror(td, errno, "pipe");
151		free(sd);
152		return 1;
153	}
154
155	td->io_ops->data = sd;
156	return 0;
157}
158
159static struct ioengine_ops ioengine = {
160	.name		= "splice",
161	.version	= FIO_IOOPS_VERSION,
162	.init		= fio_spliceio_init,
163	.queue		= fio_spliceio_queue,
164	.cleanup	= fio_spliceio_cleanup,
165	.open_file	= generic_open_file,
166	.close_file	= generic_close_file,
167	.flags		= FIO_SYNCIO,
168};
169
170#else /* FIO_HAVE_SPLICE */
171
172/*
173 * When we have a proper configure system in place, we simply wont build
174 * and install this io engine. For now install a crippled version that
175 * just complains and fails to load.
176 */
177static int fio_spliceio_init(struct thread_data fio_unused *td)
178{
179	fprintf(stderr, "fio: splice not available\n");
180	return 1;
181}
182
183static struct ioengine_ops ioengine = {
184	.name		= "splice",
185	.version	= FIO_IOOPS_VERSION,
186	.init		= fio_spliceio_init,
187};
188
189#endif
190
191static void fio_init fio_spliceio_register(void)
192{
193	register_ioengine(&ioengine);
194}
195
196static void fio_exit fio_spliceio_unregister(void)
197{
198	unregister_ioengine(&ioengine);
199}
200