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9f36eaed MJ |
1 | /* SPDX-License-Identifier: GPL-2.0 |
2 | * | |
f3bc08c5 MD |
3 | * ring_buffer_splice.c |
4 | * | |
5 | * Copyright (C) 2002-2005 - Tom Zanussi <zanussi@us.ibm.com>, IBM Corp | |
6 | * Copyright (C) 1999-2005 - Karim Yaghmour <karim@opersys.com> | |
886d51a3 | 7 | * Copyright (C) 2008-2012 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
f3bc08c5 | 8 | * |
886d51a3 | 9 | * Re-using code from kernel/relay.c, which is why it is licensed under |
9f36eaed | 10 | * the GPL-2.0. |
f3bc08c5 MD |
11 | */ |
12 | ||
13 | #include <linux/module.h> | |
14 | #include <linux/fs.h> | |
989f58e8 | 15 | #include <linux/version.h> |
f3bc08c5 | 16 | |
c075712b MD |
17 | #include <wrapper/splice.h> |
18 | #include <wrapper/ringbuffer/backend.h> | |
19 | #include <wrapper/ringbuffer/frontend.h> | |
20 | #include <wrapper/ringbuffer/vfs.h> | |
f3bc08c5 MD |
21 | |
22 | #if 0 | |
23 | #define printk_dbg(fmt, args...) printk(fmt, args) | |
24 | #else | |
25 | #define printk_dbg(fmt, args...) | |
26 | #endif | |
27 | ||
d83004aa JD |
28 | loff_t vfs_lib_ring_buffer_no_llseek(struct file *file, loff_t offset, |
29 | int origin) | |
f3bc08c5 MD |
30 | { |
31 | return -ESPIPE; | |
32 | } | |
d83004aa | 33 | EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_no_llseek); |
f3bc08c5 MD |
34 | |
35 | /* | |
36 | * Release pages from the buffer so splice pipe_to_file can move them. | |
37 | * Called after the pipe has been populated with buffer pages. | |
38 | */ | |
39 | static void lib_ring_buffer_pipe_buf_release(struct pipe_inode_info *pipe, | |
40 | struct pipe_buffer *pbuf) | |
41 | { | |
42 | __free_page(pbuf->page); | |
43 | } | |
44 | ||
45 | static const struct pipe_buf_operations ring_buffer_pipe_buf_ops = { | |
812026fc | 46 | #if (LINUX_VERSION_CODE < KERNEL_VERSION(5,1,0)) |
f3bc08c5 | 47 | .can_merge = 0, |
812026fc | 48 | #endif |
989f58e8 | 49 | #if (LINUX_VERSION_CODE < KERNEL_VERSION(3,15,0)) |
f3bc08c5 MD |
50 | .map = generic_pipe_buf_map, |
51 | .unmap = generic_pipe_buf_unmap, | |
989f58e8 | 52 | #endif |
f3bc08c5 MD |
53 | .confirm = generic_pipe_buf_confirm, |
54 | .release = lib_ring_buffer_pipe_buf_release, | |
55 | .steal = generic_pipe_buf_steal, | |
56 | .get = generic_pipe_buf_get, | |
57 | }; | |
58 | ||
59 | /* | |
60 | * Page release operation after splice pipe_to_file ends. | |
61 | */ | |
62 | static void lib_ring_buffer_page_release(struct splice_pipe_desc *spd, | |
63 | unsigned int i) | |
64 | { | |
65 | __free_page(spd->pages[i]); | |
66 | } | |
67 | ||
68 | /* | |
69 | * subbuf_splice_actor - splice up to one subbuf's worth of data | |
70 | */ | |
71 | static int subbuf_splice_actor(struct file *in, | |
72 | loff_t *ppos, | |
73 | struct pipe_inode_info *pipe, | |
74 | size_t len, | |
d83004aa JD |
75 | unsigned int flags, |
76 | struct lib_ring_buffer *buf) | |
f3bc08c5 | 77 | { |
f3bc08c5 | 78 | struct channel *chan = buf->backend.chan; |
5a8fd222 | 79 | const struct lib_ring_buffer_config *config = &chan->backend.config; |
f3bc08c5 MD |
80 | unsigned int poff, subbuf_pages, nr_pages; |
81 | struct page *pages[PIPE_DEF_BUFFERS]; | |
82 | struct partial_page partial[PIPE_DEF_BUFFERS]; | |
83 | struct splice_pipe_desc spd = { | |
84 | .pages = pages, | |
85 | .nr_pages = 0, | |
86 | .partial = partial, | |
e2833bed | 87 | #if (LINUX_VERSION_CODE < KERNEL_VERSION(4,12,0)) |
f3bc08c5 | 88 | .flags = flags, |
e2833bed | 89 | #endif |
f3bc08c5 MD |
90 | .ops = &ring_buffer_pipe_buf_ops, |
91 | .spd_release = lib_ring_buffer_page_release, | |
92 | }; | |
88dfd899 | 93 | unsigned long consumed_old, roffset; |
f3bc08c5 MD |
94 | unsigned long bytes_avail; |
95 | ||
96 | /* | |
97 | * Check that a GET_SUBBUF ioctl has been done before. | |
98 | */ | |
99 | WARN_ON(atomic_long_read(&buf->active_readers) != 1); | |
100 | consumed_old = lib_ring_buffer_get_consumed(config, buf); | |
101 | consumed_old += *ppos; | |
f3bc08c5 MD |
102 | |
103 | /* | |
104 | * Adjust read len, if longer than what is available. | |
105 | * Max read size is 1 subbuffer due to get_subbuf/put_subbuf for | |
106 | * protection. | |
107 | */ | |
108 | bytes_avail = chan->backend.subbuf_size; | |
109 | WARN_ON(bytes_avail > chan->backend.buf_size); | |
110 | len = min_t(size_t, len, bytes_avail); | |
111 | subbuf_pages = bytes_avail >> PAGE_SHIFT; | |
112 | nr_pages = min_t(unsigned int, subbuf_pages, PIPE_DEF_BUFFERS); | |
113 | roffset = consumed_old & PAGE_MASK; | |
114 | poff = consumed_old & ~PAGE_MASK; | |
115 | printk_dbg(KERN_DEBUG "SPLICE actor len %zu pos %zd write_pos %ld\n", | |
116 | len, (ssize_t)*ppos, lib_ring_buffer_get_offset(config, buf)); | |
117 | ||
118 | for (; spd.nr_pages < nr_pages; spd.nr_pages++) { | |
119 | unsigned int this_len; | |
0112cb7b MD |
120 | unsigned long *pfnp, new_pfn; |
121 | struct page *new_page; | |
f3bc08c5 MD |
122 | void **virt; |
123 | ||
124 | if (!len) | |
125 | break; | |
126 | printk_dbg(KERN_DEBUG "SPLICE actor loop len %zu roffset %ld\n", | |
127 | len, roffset); | |
128 | ||
129 | /* | |
130 | * We have to replace the page we are moving into the splice | |
131 | * pipe. | |
132 | */ | |
133 | new_page = alloc_pages_node(cpu_to_node(max(buf->backend.cpu, | |
134 | 0)), | |
135 | GFP_KERNEL | __GFP_ZERO, 0); | |
136 | if (!new_page) | |
137 | break; | |
0112cb7b | 138 | new_pfn = page_to_pfn(new_page); |
f3bc08c5 | 139 | this_len = PAGE_SIZE - poff; |
0112cb7b MD |
140 | pfnp = lib_ring_buffer_read_get_pfn(&buf->backend, roffset, &virt); |
141 | spd.pages[spd.nr_pages] = pfn_to_page(*pfnp); | |
142 | *pfnp = new_pfn; | |
f3bc08c5 MD |
143 | *virt = page_address(new_page); |
144 | spd.partial[spd.nr_pages].offset = poff; | |
145 | spd.partial[spd.nr_pages].len = this_len; | |
146 | ||
147 | poff = 0; | |
148 | roffset += PAGE_SIZE; | |
149 | len -= this_len; | |
150 | } | |
151 | ||
152 | if (!spd.nr_pages) | |
153 | return 0; | |
154 | ||
90225db5 | 155 | return wrapper_splice_to_pipe(pipe, &spd); |
f3bc08c5 MD |
156 | } |
157 | ||
158 | ssize_t lib_ring_buffer_splice_read(struct file *in, loff_t *ppos, | |
159 | struct pipe_inode_info *pipe, size_t len, | |
d83004aa JD |
160 | unsigned int flags, |
161 | struct lib_ring_buffer *buf) | |
f3bc08c5 | 162 | { |
f3bc08c5 | 163 | struct channel *chan = buf->backend.chan; |
5a8fd222 | 164 | const struct lib_ring_buffer_config *config = &chan->backend.config; |
f3bc08c5 MD |
165 | ssize_t spliced; |
166 | int ret; | |
167 | ||
168 | if (config->output != RING_BUFFER_SPLICE) | |
169 | return -EINVAL; | |
170 | ||
171 | /* | |
172 | * We require ppos and length to be page-aligned for performance reasons | |
173 | * (no page copy). Size is known using the ioctl | |
174 | * RING_BUFFER_GET_PADDED_SUBBUF_SIZE, which is page-size padded. | |
175 | * We fail when the ppos or len passed is not page-sized, because splice | |
176 | * is not allowed to copy more than the length passed as parameter (so | |
177 | * the ABI does not let us silently copy more than requested to include | |
178 | * padding). | |
179 | */ | |
180 | if (*ppos != PAGE_ALIGN(*ppos) || len != PAGE_ALIGN(len)) | |
181 | return -EINVAL; | |
182 | ||
183 | ret = 0; | |
184 | spliced = 0; | |
185 | ||
186 | printk_dbg(KERN_DEBUG "SPLICE read len %zu pos %zd\n", len, | |
187 | (ssize_t)*ppos); | |
188 | while (len && !spliced) { | |
d83004aa | 189 | ret = subbuf_splice_actor(in, ppos, pipe, len, flags, buf); |
f3bc08c5 MD |
190 | printk_dbg(KERN_DEBUG "SPLICE read loop ret %d\n", ret); |
191 | if (ret < 0) | |
192 | break; | |
193 | else if (!ret) { | |
194 | if (flags & SPLICE_F_NONBLOCK) | |
195 | ret = -EAGAIN; | |
196 | break; | |
197 | } | |
198 | ||
199 | *ppos += ret; | |
200 | if (ret > len) | |
201 | len = 0; | |
202 | else | |
203 | len -= ret; | |
204 | spliced += ret; | |
205 | } | |
206 | ||
207 | if (spliced) | |
208 | return spliced; | |
209 | ||
210 | return ret; | |
211 | } | |
212 | EXPORT_SYMBOL_GPL(lib_ring_buffer_splice_read); | |
d83004aa JD |
213 | |
214 | ssize_t vfs_lib_ring_buffer_splice_read(struct file *in, loff_t *ppos, | |
215 | struct pipe_inode_info *pipe, size_t len, | |
216 | unsigned int flags) | |
217 | { | |
218 | struct lib_ring_buffer *buf = in->private_data; | |
219 | ||
220 | return lib_ring_buffer_splice_read(in, ppos, pipe, len, flags, buf); | |
221 | } | |
222 | EXPORT_SYMBOL_GPL(vfs_lib_ring_buffer_splice_read); |