1 // SPDX-License-Identifier: GPL-2.0
2 // Author: Kirill Smelkov (kirr@nexedi.com)
3 //
4 // Search for stream-like files that are using nonseekable_open and convert
5 // them to stream_open. A stream-like file is a file that does not use ppos in
6 // its read and write. Rationale for the conversion is to avoid deadlock in
7 // between read and write.
8
9 virtual report
10 virtual patch
11 virtual explain // explain decisions in the patch (SPFLAGS="-D explain")
12
13 // stream-like reader & writer - ones that do not depend on f_pos.
14 @ stream_reader @
15 identifier readstream, ppos;
16 identifier f, buf, len;
17 type loff_t;
18 @@
19 ssize_t readstream(struct file *f, char *buf, size_t len, loff_t *ppos)
20 {
21 ... when != ppos
22 }
23
24 @ stream_writer @
25 identifier writestream, ppos;
26 identifier f, buf, len;
27 type loff_t;
28 @@
29 ssize_t writestream(struct file *f, const char *buf, size_t len, loff_t *ppos)
30 {
31 ... when != ppos
32 }
33
34
35 // a function that blocks
36 @ blocks @
37 identifier block_f;
38 identifier wait =~ "^wait_.*";
39 @@
40 block_f(...) {
41 ... when exists
42 wait(...)
43 ... when exists
44 }
45
46 // stream_reader that can block inside.
47 //
48 // XXX wait_* can be called not directly from current function (e.g. func -> f -> g -> wait())
49 // XXX currently reader_blocks supports only direct and 1-level indirect cases.
50 @ reader_blocks_direct @
51 identifier stream_reader.readstream;
52 identifier wait =~ "^wait_.*";
53 @@
54 readstream(...)
55 {
56 ... when exists
57 wait(...)
58 ... when exists
59 }
60
61 @ reader_blocks_1 @
62 identifier stream_reader.readstream;
63 identifier blocks.block_f;
64 @@
65 readstream(...)
66 {
67 ... when exists
68 block_f(...)
69 ... when exists
70 }
71
72 @ reader_blocks depends on reader_blocks_direct || reader_blocks_1 @
73 identifier stream_reader.readstream;
74 @@
75 readstream(...) {
76 ...
77 }
78
79
80 // file_operations + whether they have _any_ .read, .write, .llseek ... at all.
81 //
82 // XXX add support for file_operations xxx[N] = ... (sound/core/pcm_native.c)
83 @ fops0 @
84 identifier fops;
85 @@
86 struct file_operations fops = {
87 ...
88 };
89
90 @ has_read @
91 identifier fops0.fops;
92 identifier read_f;
93 @@
94 struct file_operations fops = {
95 .read = read_f,
96 };
97
98 @ has_read_iter @
99 identifier fops0.fops;
100 identifier read_iter_f;
101 @@
102 struct file_operations fops = {
103 .read_iter = read_iter_f,
104 };
105
106 @ has_write @
107 identifier fops0.fops;
108 identifier write_f;
109 @@
110 struct file_operations fops = {
111 .write = write_f,
112 };
113
114 @ has_write_iter @
115 identifier fops0.fops;
116 identifier write_iter_f;
117 @@
118 struct file_operations fops = {
119 .write_iter = write_iter_f,
120 };
121
122 @ has_llseek @
123 identifier fops0.fops;
124 identifier llseek_f;
125 @@
126 struct file_operations fops = {
127 .llseek = llseek_f,
128 };
129
130 @ has_no_llseek @
131 identifier fops0.fops;
132 @@
133 struct file_operations fops = {
134 };
135
136 @ has_noop_llseek @
137 identifier fops0.fops;
138 @@
139 struct file_operations fops = {
140 .llseek = noop_llseek,
141 };
142
143 @ has_mmap @
144 identifier fops0.fops;
145 identifier mmap_f;
146 @@
147 struct file_operations fops = {
148 .mmap = mmap_f,
149 };
150
151 @ has_copy_file_range @
152 identifier fops0.fops;
153 identifier copy_file_range_f;
154 @@
155 struct file_operations fops = {
156 .copy_file_range = copy_file_range_f,
157 };
158
159 @ has_remap_file_range @
160 identifier fops0.fops;
161 identifier remap_file_range_f;
162 @@
163 struct file_operations fops = {
164 .remap_file_range = remap_file_range_f,
165 };
166
167 @ has_splice_read @
168 identifier fops0.fops;
169 identifier splice_read_f;
170 @@
171 struct file_operations fops = {
172 .splice_read = splice_read_f,
173 };
174
175 @ has_splice_write @
176 identifier fops0.fops;
177 identifier splice_write_f;
178 @@
179 struct file_operations fops = {
180 .splice_write = splice_write_f,
181 };
182
183
184 // file_operations that is candidate for stream_open conversion - it does not
185 // use mmap and other methods that assume @offset access to file.
186 //
187 // XXX for simplicity require no .{read/write}_iter and no .splice_{read/write} for now.
188 // XXX maybe_steam.fops cannot be used in other rules - it gives "bad rule maybe_stream or bad variable fops".
189 @ maybe_stream depends on (!has_llseek || has_no_llseek || has_noop_llseek) && !has_mmap && !has_copy_file_range && !has_remap_file_range && !has_read_iter && !has_write_iter && !has_splice_read && !has_splice_write @
190 identifier fops0.fops;
191 @@
192 struct file_operations fops = {
193 };
194
195
196 // ---- conversions ----
197
198 // XXX .open = nonseekable_open -> .open = stream_open
199 // XXX .open = func -> openfunc -> nonseekable_open
200
201 // read & write
202 //
203 // if both are used in the same file_operations together with an opener -
204 // under that conditions we can use stream_open instead of nonseekable_open.
205 @ fops_rw depends on maybe_stream @
206 identifier fops0.fops, openfunc;
207 identifier stream_reader.readstream;
208 identifier stream_writer.writestream;
209 @@
210 struct file_operations fops = {
211 .open = openfunc,
212 .read = readstream,
213 .write = writestream,
214 };
215
216 @ report_rw depends on report @
217 identifier fops_rw.openfunc;
218 position p1;
219 @@
220 openfunc(...) {
221 <...
222 nonseekable_open@p1
223 ...>
224 }
225
226 @ script:python depends on report && reader_blocks @
227 fops << fops0.fops;
228 p << report_rw.p1;
229 @@
230 coccilib.report.print_report(p[0],
231 "ERROR: %s: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix." % (fops,))
232
233 @ script:python depends on report && !reader_blocks @
234 fops << fops0.fops;
235 p << report_rw.p1;
236 @@
237 coccilib.report.print_report(p[0],
238 "WARNING: %s: .read() and .write() have stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
239
240
241 @ explain_rw_deadlocked depends on explain && reader_blocks @
242 identifier fops_rw.openfunc;
243 @@
244 openfunc(...) {
245 <...
246 - nonseekable_open
247 + nonseekable_open /* read & write (was deadlock) */
248 ...>
249 }
250
251
252 @ explain_rw_nodeadlock depends on explain && !reader_blocks @
253 identifier fops_rw.openfunc;
254 @@
255 openfunc(...) {
256 <...
257 - nonseekable_open
258 + nonseekable_open /* read & write (no direct deadlock) */
259 ...>
260 }
261
262 @ patch_rw depends on patch @
263 identifier fops_rw.openfunc;
264 @@
265 openfunc(...) {
266 <...
267 - nonseekable_open
268 + stream_open
269 ...>
270 }
271
272
273 // read, but not write
274 @ fops_r depends on maybe_stream && !has_write @
275 identifier fops0.fops, openfunc;
276 identifier stream_reader.readstream;
277 @@
278 struct file_operations fops = {
279 .open = openfunc,
280 .read = readstream,
281 };
282
283 @ report_r depends on report @
284 identifier fops_r.openfunc;
285 position p1;
286 @@
287 openfunc(...) {
288 <...
289 nonseekable_open@p1
290 ...>
291 }
292
293 @ script:python depends on report @
294 fops << fops0.fops;
295 p << report_r.p1;
296 @@
297 coccilib.report.print_report(p[0],
298 "WARNING: %s: .read() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
299
300 @ explain_r depends on explain @
301 identifier fops_r.openfunc;
302 @@
303 openfunc(...) {
304 <...
305 - nonseekable_open
306 + nonseekable_open /* read only */
307 ...>
308 }
309
310 @ patch_r depends on patch @
311 identifier fops_r.openfunc;
312 @@
313 openfunc(...) {
314 <...
315 - nonseekable_open
316 + stream_open
317 ...>
318 }
319
320
321 // write, but not read
322 @ fops_w depends on maybe_stream && !has_read @
323 identifier fops0.fops, openfunc;
324 identifier stream_writer.writestream;
325 @@
326 struct file_operations fops = {
327 .open = openfunc,
328 .write = writestream,
329 };
330
331 @ report_w depends on report @
332 identifier fops_w.openfunc;
333 position p1;
334 @@
335 openfunc(...) {
336 <...
337 nonseekable_open@p1
338 ...>
339 }
340
341 @ script:python depends on report @
342 fops << fops0.fops;
343 p << report_w.p1;
344 @@
345 coccilib.report.print_report(p[0],
346 "WARNING: %s: .write() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
347
348 @ explain_w depends on explain @
349 identifier fops_w.openfunc;
350 @@
351 openfunc(...) {
352 <...
353 - nonseekable_open
354 + nonseekable_open /* write only */
355 ...>
356 }
357
358 @ patch_w depends on patch @
359 identifier fops_w.openfunc;
360 @@
361 openfunc(...) {
362 <...
363 - nonseekable_open
364 + stream_open
365 ...>
366 }
367
368
369 // no read, no write - don't change anything
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