splice.c revision 67bf982340d95ca98098ea050b54b4c7adb116c0 
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#include <sys/mman.h>
15
16#include "../fio.h"
17
18struct spliceio_data {
19	int pipe[2];
20	int vmsplice_to_user;
21	int vmsplice_to_user_map;
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, mmap_len;
79	off_t offset;
80	void *p, *map;
81
82	ret = 0;
83	offset = io_u->offset;
84	mmap_len = buflen = io_u->xfer_buflen;
85
86	if (sd->vmsplice_to_user_map) {
87		map = mmap(io_u->xfer_buf, buflen, PROT_READ, MAP_PRIVATE|OS_MAP_ANON, 0, 0);
88		if (map == MAP_FAILED) {
89			td_verror(td, errno, "mmap io_u");
90			return -1;
91		}
92
93		p = map;
94	} else {
95		map = NULL;
96		p = io_u->xfer_buf;
97	}
98
99	while (buflen) {
100		int this_len = buflen;
101		int flags = 0;
102
103		if (this_len > SPLICE_DEF_SIZE) {
104			this_len = SPLICE_DEF_SIZE;
105			flags = SPLICE_F_MORE;
106		}
107
108		ret = splice(f->fd, &offset, sd->pipe[1], NULL, this_len,flags);
109		if (ret < 0) {
110			if (errno == ENODATA || errno == EAGAIN)
111				continue;
112
113			td_verror(td, errno, "splice-from-fd");
114			break;
115		}
116
117		buflen -= ret;
118		iov.iov_base = p;
119		iov.iov_len = ret;
120
121		while (iov.iov_len) {
122			ret = vmsplice(sd->pipe[0], &iov, 1, SPLICE_F_MOVE);
123			if (ret < 0) {
124				if (errno == EFAULT &&
125				    sd->vmsplice_to_user_map) {
126					sd->vmsplice_to_user_map = 0;
127					munmap(map, mmap_len);
128					map = NULL;
129					p = io_u->xfer_buf;
130					iov.iov_base = p;
131					continue;
132				}
133				if (errno == EBADF) {
134					ret = -EBADF;
135					break;
136				}
137				td_verror(td, errno, "vmsplice");
138				break;
139			} else if (!ret) {
140				td_verror(td, ENODATA, "vmsplice");
141				ret = -1;
142				break;
143			}
144
145			iov.iov_len -= ret;
146			iov.iov_base += ret;
147			p += ret;
148		}
149		if (ret < 0)
150			break;
151	}
152
153	if (sd->vmsplice_to_user_map && munmap(map, mmap_len) < 0) {
154		td_verror(td, errno, "munnap io_u");
155		return -1;
156	}
157	if (ret < 0)
158		return ret;
159
160	return io_u->xfer_buflen;
161}
162
163/*
164 * For splice writing, we can vmsplice our data buffer directly into a
165 * pipe and then splice that to a file.
166 */
167static int fio_splice_write(struct thread_data *td, struct io_u *io_u)
168{
169	struct spliceio_data *sd = td->io_ops->data;
170	struct iovec iov = {
171		.iov_base = io_u->xfer_buf,
172		.iov_len = io_u->xfer_buflen,
173	};
174	struct pollfd pfd = { .fd = sd->pipe[1], .events = POLLOUT, };
175	struct fio_file *f = io_u->file;
176	off_t off = io_u->offset;
177	int ret, ret2;
178
179	while (iov.iov_len) {
180		if (poll(&pfd, 1, -1) < 0)
181			return errno;
182
183		ret = vmsplice(sd->pipe[1], &iov, 1, SPLICE_F_NONBLOCK);
184		if (ret < 0)
185			return -errno;
186
187		iov.iov_len -= ret;
188		iov.iov_base += ret;
189
190		while (ret) {
191			ret2 = splice(sd->pipe[0], NULL, f->fd, &off, ret, 0);
192			if (ret2 < 0)
193				return -errno;
194
195			ret -= ret2;
196		}
197	}
198
199	return io_u->xfer_buflen;
200}
201
202static int fio_spliceio_queue(struct thread_data *td, struct io_u *io_u)
203{
204	struct spliceio_data *sd = td->io_ops->data;
205	int ret = 0;
206
207	fio_ro_check(td, io_u);
208
209	if (io_u->ddir == DDIR_READ) {
210		if (sd->vmsplice_to_user) {
211			ret = fio_splice_read(td, io_u);
212			/*
213			 * This kernel doesn't support vmsplice to user
214			 * space. Reset the vmsplice_to_user flag, so that
215			 * we retry below and don't hit this path again.
216			 */
217			if (ret == -EBADF)
218				sd->vmsplice_to_user = 0;
219		}
220		if (!sd->vmsplice_to_user)
221			ret = fio_splice_read_old(td, io_u);
222	} else if (io_u->ddir == DDIR_WRITE)
223		ret = fio_splice_write(td, io_u);
224	else if (io_u->ddir == DDIR_TRIM)
225		ret = do_io_u_trim(td, io_u);
226	else
227		ret = do_io_u_sync(td, io_u);
228
229	if (ret != (int) io_u->xfer_buflen) {
230		if (ret >= 0) {
231			io_u->resid = io_u->xfer_buflen - ret;
232			io_u->error = 0;
233			return FIO_Q_COMPLETED;
234		} else
235			io_u->error = errno;
236	}
237
238	if (io_u->error) {
239		td_verror(td, io_u->error, "xfer");
240		if (io_u->error == EINVAL)
241			log_err("fio: looks like splice doesn't work on this"
242					" file system\n");
243	}
244
245	return FIO_Q_COMPLETED;
246}
247
248static void fio_spliceio_cleanup(struct thread_data *td)
249{
250	struct spliceio_data *sd = td->io_ops->data;
251
252	if (sd) {
253		close(sd->pipe[0]);
254		close(sd->pipe[1]);
255		free(sd);
256	}
257}
258
259static int fio_spliceio_init(struct thread_data *td)
260{
261	struct spliceio_data *sd = malloc(sizeof(*sd));
262
263	if (pipe(sd->pipe) < 0) {
264		td_verror(td, errno, "pipe");
265		free(sd);
266		return 1;
267	}
268
269	/*
270	 * Assume this work, we'll reset this if it doesn't
271	 */
272	sd->vmsplice_to_user = 1;
273
274	/*
275	 * Works with "real" vmsplice to user, eg mapping pages directly.
276	 * Reset if we fail.
277	 */
278	sd->vmsplice_to_user_map = 1;
279
280	/*
281	 * And if vmsplice_to_user works, we definitely need aligned
282	 * buffers. Just set ->odirect to force that.
283	 */
284	if (td_read(td))
285		td->o.mem_align = 1;
286
287	td->io_ops->data = sd;
288	return 0;
289}
290
291static struct ioengine_ops ioengine = {
292	.name		= "splice",
293	.version	= FIO_IOOPS_VERSION,
294	.init		= fio_spliceio_init,
295	.queue		= fio_spliceio_queue,
296	.cleanup	= fio_spliceio_cleanup,
297	.open_file	= generic_open_file,
298	.close_file	= generic_close_file,
299	.get_file_size	= generic_get_file_size,
300	.flags		= FIO_SYNCIO | FIO_PIPEIO,
301};
302
303static void fio_init fio_spliceio_register(void)
304{
305	register_ioengine(&ioengine);
306}
307
308static void fio_exit fio_spliceio_unregister(void)
309{
310	unregister_ioengine(&ioengine);
311}
312