Merge branch 'jt/cache-tree-avoid-lazy-fetch-during-merge'
[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 struct tempfile *new_tempfile(void)
95 {
96 struct tempfile *tempfile = xmalloc(sizeof(*tempfile));
97 tempfile->fd = -1;
98 tempfile->fp = NULL;
99 tempfile->active = 0;
100 tempfile->owner = 0;
101 INIT_LIST_HEAD(&tempfile->list);
102 strbuf_init(&tempfile->filename, 0);
103 return tempfile;
104 }
105
106 static void activate_tempfile(struct tempfile *tempfile)
107 {
108 static int initialized;
109
110 if (is_tempfile_active(tempfile))
111 BUG("activate_tempfile called for active object");
112
113 if (!initialized) {
114 sigchain_push_common(remove_tempfiles_on_signal);
115 atexit(remove_tempfiles_on_exit);
116 initialized = 1;
117 }
118
119 volatile_list_add(&tempfile->list, &tempfile_list);
120 tempfile->owner = getpid();
121 tempfile->active = 1;
122 }
123
124 static void deactivate_tempfile(struct tempfile *tempfile)
125 {
126 tempfile->active = 0;
127 strbuf_release(&tempfile->filename);
128 volatile_list_del(&tempfile->list);
129 free(tempfile);
130 }
131
132 /* Make sure errno contains a meaningful value on error */
133 struct tempfile *create_tempfile(const char *path)
134 {
135 struct tempfile *tempfile = new_tempfile();
136
137 strbuf_add_absolute_path(&tempfile->filename, path);
138 tempfile->fd = open(tempfile->filename.buf,
139 O_RDWR | O_CREAT | O_EXCL | O_CLOEXEC, 0666);
140 if (O_CLOEXEC && tempfile->fd < 0 && errno == EINVAL)
141 /* Try again w/o O_CLOEXEC: the kernel might not support it */
142 tempfile->fd = open(tempfile->filename.buf,
143 O_RDWR | O_CREAT | O_EXCL, 0666);
144 if (tempfile->fd < 0) {
145 deactivate_tempfile(tempfile);
146 return NULL;
147 }
148 activate_tempfile(tempfile);
149 if (adjust_shared_perm(tempfile->filename.buf)) {
150 int save_errno = errno;
151 error("cannot fix permission bits on %s", tempfile->filename.buf);
152 delete_tempfile(&tempfile);
153 errno = save_errno;
154 return NULL;
155 }
156
157 return tempfile;
158 }
159
160 struct tempfile *register_tempfile(const char *path)
161 {
162 struct tempfile *tempfile = new_tempfile();
163 strbuf_add_absolute_path(&tempfile->filename, path);
164 activate_tempfile(tempfile);
165 return tempfile;
166 }
167
168 struct tempfile *mks_tempfile_sm(const char *filename_template, int suffixlen, int mode)
169 {
170 struct tempfile *tempfile = new_tempfile();
171
172 strbuf_add_absolute_path(&tempfile->filename, filename_template);
173 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
174 if (tempfile->fd < 0) {
175 deactivate_tempfile(tempfile);
176 return NULL;
177 }
178 activate_tempfile(tempfile);
179 return tempfile;
180 }
181
182 struct tempfile *mks_tempfile_tsm(const char *filename_template, int suffixlen, int mode)
183 {
184 struct tempfile *tempfile = new_tempfile();
185 const char *tmpdir;
186
187 tmpdir = getenv("TMPDIR");
188 if (!tmpdir)
189 tmpdir = "/tmp";
190
191 strbuf_addf(&tempfile->filename, "%s/%s", tmpdir, filename_template);
192 tempfile->fd = git_mkstemps_mode(tempfile->filename.buf, suffixlen, mode);
193 if (tempfile->fd < 0) {
194 deactivate_tempfile(tempfile);
195 return NULL;
196 }
197 activate_tempfile(tempfile);
198 return tempfile;
199 }
200
201 struct tempfile *xmks_tempfile_m(const char *filename_template, int mode)
202 {
203 struct tempfile *tempfile;
204 struct strbuf full_template = STRBUF_INIT;
205
206 strbuf_add_absolute_path(&full_template, filename_template);
207 tempfile = mks_tempfile_m(full_template.buf, mode);
208 if (!tempfile)
209 die_errno("Unable to create temporary file '%s'",
210 full_template.buf);
211
212 strbuf_release(&full_template);
213 return tempfile;
214 }
215
216 FILE *fdopen_tempfile(struct tempfile *tempfile, const char *mode)
217 {
218 if (!is_tempfile_active(tempfile))
219 BUG("fdopen_tempfile() called for inactive object");
220 if (tempfile->fp)
221 BUG("fdopen_tempfile() called for open object");
222
223 tempfile->fp = fdopen(tempfile->fd, mode);
224 return tempfile->fp;
225 }
226
227 const char *get_tempfile_path(struct tempfile *tempfile)
228 {
229 if (!is_tempfile_active(tempfile))
230 BUG("get_tempfile_path() called for inactive object");
231 return tempfile->filename.buf;
232 }
233
234 int get_tempfile_fd(struct tempfile *tempfile)
235 {
236 if (!is_tempfile_active(tempfile))
237 BUG("get_tempfile_fd() called for inactive object");
238 return tempfile->fd;
239 }
240
241 FILE *get_tempfile_fp(struct tempfile *tempfile)
242 {
243 if (!is_tempfile_active(tempfile))
244 BUG("get_tempfile_fp() called for inactive object");
245 return tempfile->fp;
246 }
247
248 int close_tempfile_gently(struct tempfile *tempfile)
249 {
250 int fd;
251 FILE *fp;
252 int err;
253
254 if (!is_tempfile_active(tempfile) || tempfile->fd < 0)
255 return 0;
256
257 fd = tempfile->fd;
258 fp = tempfile->fp;
259 tempfile->fd = -1;
260 if (fp) {
261 tempfile->fp = NULL;
262 if (ferror(fp)) {
263 err = -1;
264 if (!fclose(fp))
265 errno = EIO;
266 } else {
267 err = fclose(fp);
268 }
269 } else {
270 err = close(fd);
271 }
272
273 return err ? -1 : 0;
274 }
275
276 int reopen_tempfile(struct tempfile *tempfile)
277 {
278 if (!is_tempfile_active(tempfile))
279 BUG("reopen_tempfile called for an inactive object");
280 if (0 <= tempfile->fd)
281 BUG("reopen_tempfile called for an open object");
282 tempfile->fd = open(tempfile->filename.buf, O_WRONLY|O_TRUNC);
283 return tempfile->fd;
284 }
285
286 int rename_tempfile(struct tempfile **tempfile_p, const char *path)
287 {
288 struct tempfile *tempfile = *tempfile_p;
289
290 if (!is_tempfile_active(tempfile))
291 BUG("rename_tempfile called for inactive object");
292
293 if (close_tempfile_gently(tempfile)) {
294 delete_tempfile(tempfile_p);
295 return -1;
296 }
297
298 if (rename(tempfile->filename.buf, path)) {
299 int save_errno = errno;
300 delete_tempfile(tempfile_p);
301 errno = save_errno;
302 return -1;
303 }
304
305 deactivate_tempfile(tempfile);
306 *tempfile_p = NULL;
307 return 0;
308 }
309
310 void delete_tempfile(struct tempfile **tempfile_p)
311 {
312 struct tempfile *tempfile = *tempfile_p;
313
314 if (!is_tempfile_active(tempfile))
315 return;
316
317 close_tempfile_gently(tempfile);
318 unlink_or_warn(tempfile->filename.buf);
319 deactivate_tempfile(tempfile);
320 *tempfile_p = NULL;
321 }