splice.c revision 436885758c1b859392b80c616c338f9cfe9a9dfb 
1/*
2 * splice engine
3 *
4 * IO engine that transfers data by doing splices to/from pipes and
5 * the files.
6 *
7 */
8#include <stdio.h>
9#include <stdlib.h>
10#include <unistd.h>
11#include <errno.h>
12#include <assert.h>
13#include <sys/poll.h>
14
15#include "../fio.h"
16
17#ifdef FIO_HAVE_SPLICE
18
19struct spliceio_data {
20	int pipe[2];
21	int vmsplice_to_user;
22};
23
24/*
25 * vmsplice didn't use to support splicing to user space, this is the old
26 * variant of getting that job done. Doesn't make a lot of sense, but it
27 * uses splices to move data from the source into a pipe.
28 */
29static int fio_splice_read_old(struct thread_data *td, struct io_u *io_u)
30{
31	struct spliceio_data *sd = td->io_ops->data;
32	struct fio_file *f = io_u->file;
33	int ret, ret2, buflen;
34	off_t offset;
35	void *p;
36
37	offset = io_u->offset;
38	buflen = io_u->xfer_buflen;
39	p = io_u->xfer_buf;
40	while (buflen) {
41		int this_len = buflen;
42
43		if (this_len > SPLICE_DEF_SIZE)
44			this_len = SPLICE_DEF_SIZE;
45
46		ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len, SPLICE_F_MORE);
47		if (ret < 0) {
48			if (errno == ENODATA || errno == EAGAIN)
49				continue;
50
51			return -errno;
52		}
53
54		buflen -= ret;
55
56		while (ret) {
57			ret2 = read(sd->pipe[0], p, ret);
58			if (ret2 < 0)
59				return -errno;
60
61			ret -= ret2;
62			p += ret2;
63		}
64	}
65
66	return io_u->xfer_buflen;
67}
68
69/*
70 * We can now vmsplice into userspace, so do the transfer by splicing into
71 * a pipe and vmsplicing that into userspace.
72 */
73static int fio_splice_read(struct thread_data *td, struct io_u *io_u)
74{
75	struct spliceio_data *sd = td->io_ops->data;
76	struct fio_file *f = io_u->file;
77	struct iovec iov;
78	int ret, buflen;
79	off_t offset;
80	void *p;
81
82	offset = io_u->offset;
83	buflen = io_u->xfer_buflen;
84	p = io_u->xfer_buf;
85	while (buflen) {
86		int this_len = buflen;
87
88		if (this_len > SPLICE_DEF_SIZE)
89			this_len = SPLICE_DEF_SIZE;
90
91		ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len, SPLICE_F_MORE);
92		if (ret < 0) {
93			if (errno == ENODATA || errno == EAGAIN)
94				continue;
95
96			return -errno;
97		}
98
99		buflen -= ret;
100		iov.iov_base = p;
101		iov.iov_len = ret;
102		p += ret;
103
104		while (iov.iov_len) {
105			ret = vmsplice(sd->pipe[0], &iov, 1, SPLICE_F_MOVE);
106			if (ret < 0)
107				return -errno;
108			else if (!ret)
109				return -ENODATA;
110
111			iov.iov_len -= ret;
112			iov.iov_base += ret;
113		}
114	}
115
116	return io_u->xfer_buflen;
117}
118
119/*
120 * For splice writing, we can vmsplice our data buffer directly into a
121 * pipe and then splice that to a file.
122 */
123static int fio_splice_write(struct thread_data *td, struct io_u *io_u)
124{
125	struct spliceio_data *sd = td->io_ops->data;
126	struct iovec iov = {
127		.iov_base = io_u->xfer_buf,
128		.iov_len = io_u->xfer_buflen,
129	};
130	struct pollfd pfd = { .fd = sd->pipe[1], .events = POLLOUT, };
131	struct fio_file *f = io_u->file;
132	off_t off = io_u->offset;
133	int ret, ret2;
134
135	while (iov.iov_len) {
136		if (poll(&pfd, 1, -1) < 0)
137			return errno;
138
139		ret = vmsplice(sd->pipe[1], &iov, 1, SPLICE_F_NONBLOCK);
140		if (ret < 0)
141			return -errno;
142
143		iov.iov_len -= ret;
144		iov.iov_base += ret;
145
146		while (ret) {
147			ret2 = splice(sd->pipe[0], NULL, f->fd, &off, ret, 0);
148			if (ret2 < 0)
149				return -errno;
150
151			ret -= ret2;
152		}
153	}
154
155	return io_u->xfer_buflen;
156}
157
158static int fio_spliceio_queue(struct thread_data *td, struct io_u *io_u)
159{
160	struct spliceio_data *sd = td->io_ops->data;
161	int ret;
162
163	if (io_u->ddir == DDIR_READ) {
164		if (sd->vmsplice_to_user) {
165			ret = fio_splice_read(td, io_u);
166			/*
167			 * This kernel doesn't support vmsplice to user
168			 * space. Reset the vmsplice_to_user flag, so that
169			 * we retry below and don't hit this path again.
170			 */
171			if (ret == -EBADF)
172				sd->vmsplice_to_user = 0;
173		}
174		if (!sd->vmsplice_to_user)
175			ret = fio_splice_read_old(td, io_u);
176	} else if (io_u->ddir == DDIR_WRITE)
177		ret = fio_splice_write(td, io_u);
178	else
179		ret = fsync(io_u->file->fd);
180
181	if (ret != (int) io_u->xfer_buflen) {
182		if (ret >= 0) {
183			io_u->resid = io_u->xfer_buflen - ret;
184			io_u->error = 0;
185			return FIO_Q_COMPLETED;
186		} else
187			io_u->error = errno;
188	}
189
190	if (io_u->error)
191		td_verror(td, io_u->error, "xfer");
192
193	return FIO_Q_COMPLETED;
194}
195
196static void fio_spliceio_cleanup(struct thread_data *td)
197{
198	struct spliceio_data *sd = td->io_ops->data;
199
200	if (sd) {
201		close(sd->pipe[0]);
202		close(sd->pipe[1]);
203		free(sd);
204		td->io_ops->data = NULL;
205	}
206}
207
208static int fio_spliceio_init(struct thread_data *td)
209{
210	struct spliceio_data *sd = malloc(sizeof(*sd));
211
212	if (pipe(sd->pipe) < 0) {
213		td_verror(td, errno, "pipe");
214		free(sd);
215		return 1;
216	}
217
218	/*
219	 * Assume this work, we'll reset this if it doesn't
220	 */
221	sd->vmsplice_to_user = 1;
222
223	td->io_ops->data = sd;
224	return 0;
225}
226
227static struct ioengine_ops ioengine = {
228	.name		= "splice",
229	.version	= FIO_IOOPS_VERSION,
230	.init		= fio_spliceio_init,
231	.queue		= fio_spliceio_queue,
232	.cleanup	= fio_spliceio_cleanup,
233	.open_file	= generic_open_file,
234	.close_file	= generic_close_file,
235	.flags		= FIO_SYNCIO,
236};
237
238#else /* FIO_HAVE_SPLICE */
239
240/*
241 * When we have a proper configure system in place, we simply wont build
242 * and install this io engine. For now install a crippled version that
243 * just complains and fails to load.
244 */
245static int fio_spliceio_init(struct thread_data fio_unused *td)
246{
247	fprintf(stderr, "fio: splice not available\n");
248	return 1;
249}
250
251static struct ioengine_ops ioengine = {
252	.name		= "splice",
253	.version	= FIO_IOOPS_VERSION,
254	.init		= fio_spliceio_init,
255};
256
257#endif
258
259static void fio_init fio_spliceio_register(void)
260{
261	register_ioengine(&ioengine);
262}
263
264static void fio_exit fio_spliceio_unregister(void)
265{
266	unregister_ioengine(&ioengine);
267}
268