tempfile: remove deactivated list entries
[git/git.git] / tempfile.c
1 /*
2 * State diagram and cleanup
3 * -------------------------
4 *
5 * If the program exits while a temporary file is active, we want to
6 * make sure that we remove it. This is done by remembering the active
7 * temporary files in a linked list, `tempfile_list`. An `atexit(3)`
8 * handler and a signal handler are registered, to clean up any active
9 * temporary files.
10 *
11 * Because the signal handler can run at any time, `tempfile_list` and
12 * the `tempfile` objects that comprise it must be kept in
13 * self-consistent states at all times.
14 *
15 * The possible states of a `tempfile` object are as follows:
16 *
17 * - Uninitialized. In this state the object's `on_list` field must be
18 * zero but the rest of its contents need not be initialized. As
19 * soon as the object is used in any way, it is irrevocably
20 * registered in `tempfile_list`, and `on_list` is set.
21 *
22 * - Active, file open (after `create_tempfile()` or
23 * `reopen_tempfile()`). In this state:
24 *
25 * - the temporary file exists
26 * - `active` is set
27 * - `filename` holds the filename of the temporary file
28 * - `fd` holds a file descriptor open for writing to it
29 * - `fp` holds a pointer to an open `FILE` object if and only if
30 * `fdopen_tempfile()` has been called on the object
31 * - `owner` holds the PID of the process that created the file
32 *
33 * - Active, file closed (after `close_tempfile_gently()`). Same
34 * as the previous state, except that the temporary file is closed,
35 * `fd` is -1, and `fp` is `NULL`.
36 *
37 * - Inactive (after `delete_tempfile()`, `rename_tempfile()`, or a
38 * failed attempt to create a temporary file). In this state:
39 *
40 * - `active` is unset
41 * - `filename` is empty (usually, though there are transitory
42 * states in which this condition doesn't hold). Client code should
43 * *not* rely on the filename being empty in this state.
44 * - `fd` is -1 and `fp` is `NULL`
45 * - the object is removed from `tempfile_list` (but could be used again)
46 *
47 * A temporary file is owned by the process that created it. The
48 * `tempfile` has an `owner` field that records the owner's PID. This
49 * field is used to prevent a forked process from deleting a temporary
50 * file created by its parent.
51 */
52
53 #include "cache.h"
54 #include "tempfile.h"
55 #include "sigchain.h"
56
57 static VOLATILE_LIST_HEAD(tempfile_list);
58
59 static void remove_tempfiles(int in_signal_handler)
60 {
61 pid_t me = getpid();
62 volatile struct volatile_list_head *pos;
63
64 list_for_each(pos, &tempfile_list) {
65 struct tempfile *p = list_entry(pos, struct tempfile, list);
66
67 if (!is_tempfile_active(p) || p->owner != me)
68 continue;
69
70 if (p->fd >= 0)
71 close(p->fd);
72
73 if (in_signal_handler)
74 unlink(p->filename.buf);
75 else
76 unlink_or_warn(p->filename.buf);
77
78 p->active = 0;
79 }
80 }
81
82 static void remove_tempfiles_on_exit(void)
83 {
84 remove_tempfiles(0);
85 }
86
87 static void remove_tempfiles_on_signal(int signo)
88 {
89 remove_tempfiles(1);
90 sigchain_pop(signo);
91 raise(signo);
92 }
93
94 static void prepare_tempfile_object(struct tempfile *tempfile)
95 {
96 tempfile->fd = -1;
97 tempfile->fp = NULL;
98 tempfile->active = 0;
99 tempfile->owner = 0;
100 INIT_LIST_HEAD(&tempfile->list);
101 strbuf_init(&tempfile->filename, 0);
102 }
103
104 static void activate_tempfile(struct tempfile *tempfile)
105 {
106 static int initialized;
107
108 if (is_tempfile_active(tempfile))
109 BUG("activate_tempfile called for active object");
110
111 if (!initialized) {
112 sigchain_push_common(remove_tempfiles_on_signal);
113 atexit(remove_tempfiles_on_exit);
114 initialized = 1;
115 }
116
117 volatile_list_add(&tempfile->list, &tempfile_list);
118 tempfile->owner = getpid();
119 tempfile->active = 1;
120 }
121
122 static void deactivate_tempfile(struct tempfile *tempfile)
123 {
124 tempfile->active = 0;
125 strbuf_release(&tempfile->filename);
126 volatile_list_del(&tempfile->list);
127 }
128
129 /* Make sure errno contains a meaningful value on error */
130 int create_tempfile(struct tempfile *tempfile, const char *path)
131 {
132 prepare_tempfile_object(tempfile);
133
134 strbuf_add_absolute_path(&tempfile->filename, path);
135 tempfile->fd = open(tempfile->filename.buf,
136 O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
137 if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
138 /* Try again w/o O_CLOEXEC: the kernel might not support it */
139 tempfile->fd = open(tempfile->filename.buf,
140 O_RDWR | O_CREAT | O_EXCL, 0666);
141 if (tempfile->fd < 0) {
142 deactivate_tempfile(tempfile);
143 return -1;
144 }
145 activate_tempfile(tempfile);
146 if (adjust_shared_perm(tempfile->filename.buf)) {
147 int save_errno = errno;
148 error("cannot fix permission bits on %s", tempfile->filename.buf);
149 delete_tempfile(tempfile);
150 errno = save_errno;
151 return -1;
152 }
153 return tempfile->fd;
154 }
155
156 void register_tempfile(struct tempfile *tempfile, const char *path)
157 {
158 prepare_tempfile_object(tempfile);
159 strbuf_add_absolute_path(&tempfile->filename, path);
160 activate_tempfile(tempfile);
161 }
162
163 int mks_tempfile_sm(struct tempfile *tempfile,
164 const char *template, int suffixlen, int mode)
165 {
166 prepare_tempfile_object(tempfile);
167
168 strbuf_add_absolute_path(&tempfile->filename, template);
169 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
170 if (tempfile->fd < 0) {
171 deactivate_tempfile(tempfile);
172 return -1;
173 }
174 activate_tempfile(tempfile);
175 return tempfile->fd;
176 }
177
178 int mks_tempfile_tsm(struct tempfile *tempfile,
179 const char *template, int suffixlen, int mode)
180 {
181 const char *tmpdir;
182
183 prepare_tempfile_object(tempfile);
184
185 tmpdir = getenv("TMPDIR");
186 if (!tmpdir)
187 tmpdir = "/tmp";
188
189 strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, template);
190 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
191 if (tempfile->fd < 0) {
192 deactivate_tempfile(tempfile);
193 return -1;
194 }
195 activate_tempfile(tempfile);
196 return tempfile->fd;
197 }
198
199 int xmks_tempfile_m(struct tempfile *tempfile, const char *template, int mode)
200 {
201 int fd;
202 struct strbuf full_template = STRBUF_INIT;
203
204 strbuf_add_absolute_path(&full_template, template);
205 fd = mks_tempfile_m(tempfile, full_template.buf, mode);
206 if (fd < 0)
207 die_errno("Unable to create temporary file '%s'",
208 full_template.buf);
209
210 strbuf_release(&full_template);
211 return fd;
212 }
213
214 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
215 {
216 if (!is_tempfile_active(tempfile))
217 BUG("fdopen_tempfile() called for inactive object");
218 if (tempfile->fp)
219 BUG("fdopen_tempfile() called for open object");
220
221 tempfile->fp = fdopen(tempfile->fd, mode);
222 return tempfile->fp;
223 }
224
225 const char *get_tempfile_path(struct tempfile *tempfile)
226 {
227 if (!is_tempfile_active(tempfile))
228 BUG("get_tempfile_path() called for inactive object");
229 return tempfile->filename.buf;
230 }
231
232 int get_tempfile_fd(struct tempfile *tempfile)
233 {
234 if (!is_tempfile_active(tempfile))
235 BUG("get_tempfile_fd() called for inactive object");
236 return tempfile->fd;
237 }
238
239 FILE *get_tempfile_fp(struct tempfile *tempfile)
240 {
241 if (!is_tempfile_active(tempfile))
242 BUG("get_tempfile_fp() called for inactive object");
243 return tempfile->fp;
244 }
245
246 int close_tempfile_gently(struct tempfile *tempfile)
247 {
248 int fd;
249 FILE *fp;
250 int err;
251
252 if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
253 return 0;
254
255 fd = tempfile->fd;
256 fp = tempfile->fp;
257 tempfile->fd = -1;
258 if (fp) {
259 tempfile->fp = NULL;
260 if (ferror(fp)) {
261 err = -1;
262 if (!fclose(fp))
263 errno = EIO;
264 } else {
265 err = fclose(fp);
266 }
267 } else {
268 err = close(fd);
269 }
270
271 return err ? -1 : 0;
272 }
273
274 int reopen_tempfile(struct tempfile *tempfile)
275 {
276 if (!is_tempfile_active(tempfile))
277 BUG("reopen_tempfile called for an inactive object");
278 if (0 <= tempfile->fd)
279 BUG("reopen_tempfile called for an open object");
280 tempfile->fd = open(tempfile->filename.buf, O_WRONLY);
281 return tempfile->fd;
282 }
283
284 int rename_tempfile(struct tempfile *tempfile, const char *path)
285 {
286 if (!is_tempfile_active(tempfile))
287 BUG("rename_tempfile called for inactive object");
288
289 if (close_tempfile_gently(tempfile)) {
290 delete_tempfile(tempfile);
291 return -1;
292 }
293
294 if (rename(tempfile->filename.buf, path)) {
295 int save_errno = errno;
296 delete_tempfile(tempfile);
297 errno = save_errno;
298 return -1;
299 }
300
301 deactivate_tempfile(tempfile);
302 return 0;
303 }
304
305 void delete_tempfile(struct tempfile *tempfile)
306 {
307 if (!is_tempfile_active(tempfile))
308 return;
309
310 close_tempfile_gently(tempfile);
311 unlink_or_warn(tempfile->filename.buf);
312 deactivate_tempfile(tempfile);
313 }