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Commit | Line | Data |
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021b6e45 JH |
1 | /* |
2 | * Copyright (c) 2005, Junio C Hamano | |
3 | */ | |
021b6e45 | 4 | #include "cache.h" |
4a16d072 | 5 | #include "sigchain.h" |
021b6e45 | 6 | |
0a06f148 MH |
7 | /* |
8 | * File write-locks as used by Git. | |
9 | * | |
10 | * For an overview of how to use the lockfile API, please see | |
11 | * | |
12 | * Documentation/technical/api-lockfile.txt | |
13 | * | |
14 | * This module keeps track of all locked files in lock_file_list for | |
15 | * use at cleanup. This list and the lock_file objects that comprise | |
16 | * it must be kept in self-consistent states at all time, because the | |
17 | * program can be interrupted any time by a signal, in which case the | |
18 | * signal handler will walk through the list attempting to clean up | |
19 | * any open lock files. | |
20 | * | |
21 | * A lockfile is owned by the process that created it. The lock_file | |
22 | * object has an "owner" field that records its owner. This field is | |
23 | * used to prevent a forked process from closing a lockfile created by | |
24 | * its parent. | |
25 | * | |
707103fd | 26 | * The possible states of a lock_file object are as follows: |
0a06f148 MH |
27 | * |
28 | * - Uninitialized. In this state the object's on_list field must be | |
29 | * zero but the rest of its contents need not be initialized. As | |
30 | * soon as the object is used in any way, it is irrevocably | |
31 | * registered in the lock_file_list, and on_list is set. | |
32 | * | |
33 | * - Locked, lockfile open (after hold_lock_file_for_update(), | |
34 | * hold_lock_file_for_append(), or reopen_lock_file()). In this | |
707103fd MH |
35 | * state: |
36 | * - the lockfile exists | |
37 | * - active is set | |
38 | * - filename holds the filename of the lockfile | |
39 | * - fd holds a file descriptor open for writing to the lockfile | |
40 | * - owner holds the PID of the process that locked the file | |
0a06f148 | 41 | * |
8e86c155 MH |
42 | * - Locked, lockfile closed (after successful close_lock_file()). |
43 | * Same as the previous state, except that the lockfile is closed | |
44 | * and fd is -1. | |
0a06f148 | 45 | * |
8e86c155 | 46 | * - Unlocked (after commit_lock_file(), rollback_lock_file(), a |
707103fd MH |
47 | * failed attempt to lock, or a failed close_lock_file()). In this |
48 | * state: | |
49 | * - active is unset | |
cf6950d3 MH |
50 | * - filename is empty (usually, though there are transitory |
51 | * states in which this condition doesn't hold). Client code should | |
52 | * *not* rely on the filename being empty in this state. | |
707103fd MH |
53 | * - fd is -1 |
54 | * - the object is left registered in the lock_file_list, and | |
55 | * on_list is set. | |
0a06f148 MH |
56 | */ |
57 | ||
2091c506 | 58 | static struct lock_file *volatile lock_file_list; |
021b6e45 JH |
59 | |
60 | static void remove_lock_file(void) | |
61 | { | |
5e635e39 JH |
62 | pid_t me = getpid(); |
63 | ||
021b6e45 | 64 | while (lock_file_list) { |
a1754bcc MH |
65 | if (lock_file_list->owner == me) |
66 | rollback_lock_file(lock_file_list); | |
021b6e45 JH |
67 | lock_file_list = lock_file_list->next; |
68 | } | |
69 | } | |
70 | ||
71 | static void remove_lock_file_on_signal(int signo) | |
72 | { | |
73 | remove_lock_file(); | |
4a16d072 | 74 | sigchain_pop(signo); |
021b6e45 JH |
75 | raise(signo); |
76 | } | |
77 | ||
5d5a7a67 | 78 | /* |
0c0d6e86 | 79 | * path = absolute or relative path name |
5d5a7a67 | 80 | * |
0c0d6e86 MH |
81 | * Remove the last path name element from path (leaving the preceding |
82 | * "/", if any). If path is empty or the root directory ("/"), set | |
83 | * path to the empty string. | |
5d5a7a67 | 84 | */ |
0c0d6e86 | 85 | static void trim_last_path_component(struct strbuf *path) |
5d5a7a67 | 86 | { |
0c0d6e86 | 87 | int i = path->len; |
5d5a7a67 BS |
88 | |
89 | /* back up past trailing slashes, if any */ | |
0c0d6e86 MH |
90 | while (i && path->buf[i - 1] == '/') |
91 | i--; | |
5d5a7a67 BS |
92 | |
93 | /* | |
0c0d6e86 MH |
94 | * then go backwards until a slash, or the beginning of the |
95 | * string | |
5d5a7a67 | 96 | */ |
0c0d6e86 MH |
97 | while (i && path->buf[i - 1] != '/') |
98 | i--; | |
99 | ||
100 | strbuf_setlen(path, i); | |
5d5a7a67 BS |
101 | } |
102 | ||
103 | ||
104 | /* We allow "recursive" symbolic links. Only within reason, though */ | |
105 | #define MAXDEPTH 5 | |
106 | ||
107 | /* | |
6cad8053 | 108 | * path contains a path that might be a symlink. |
5d5a7a67 | 109 | * |
6cad8053 MH |
110 | * If path is a symlink, attempt to overwrite it with a path to the |
111 | * real file or directory (which may or may not exist), following a | |
112 | * chain of symlinks if necessary. Otherwise, leave path unmodified. | |
5d5a7a67 | 113 | * |
6cad8053 MH |
114 | * This is a best-effort routine. If an error occurs, path will |
115 | * either be left unmodified or will name a different symlink in a | |
116 | * symlink chain that started with the original path. | |
5d5a7a67 | 117 | */ |
6cad8053 | 118 | static void resolve_symlink(struct strbuf *path) |
5d5a7a67 BS |
119 | { |
120 | int depth = MAXDEPTH; | |
5025d845 | 121 | static struct strbuf link = STRBUF_INIT; |
5d5a7a67 BS |
122 | |
123 | while (depth--) { | |
6cad8053 | 124 | if (strbuf_readlink(&link, path->buf, path->len) < 0) |
5025d845 | 125 | break; |
5d5a7a67 | 126 | |
6cad8053 | 127 | if (is_absolute_path(link.buf)) |
5d5a7a67 | 128 | /* absolute path simply replaces p */ |
6cad8053 | 129 | strbuf_reset(path); |
0c0d6e86 | 130 | else |
5d5a7a67 | 131 | /* |
5025d845 | 132 | * link is a relative path, so replace the |
5d5a7a67 BS |
133 | * last element of p with it. |
134 | */ | |
0c0d6e86 | 135 | trim_last_path_component(path); |
6cad8053 MH |
136 | |
137 | strbuf_addbuf(path, &link); | |
5d5a7a67 | 138 | } |
5025d845 | 139 | strbuf_reset(&link); |
5d5a7a67 BS |
140 | } |
141 | ||
447ff1bf | 142 | /* Make sure errno contains a meaningful value on error */ |
acd3b9ec | 143 | static int lock_file(struct lock_file *lk, const char *path, int flags) |
021b6e45 | 144 | { |
6cad8053 MH |
145 | size_t pathlen = strlen(path); |
146 | ||
04e57d4d MH |
147 | if (!lock_file_list) { |
148 | /* One-time initialization */ | |
149 | sigchain_push_common(remove_lock_file_on_signal); | |
150 | atexit(remove_lock_file); | |
151 | } | |
152 | ||
707103fd MH |
153 | if (lk->active) |
154 | die("BUG: cannot lock_file(\"%s\") using active struct lock_file", | |
155 | path); | |
04e57d4d MH |
156 | if (!lk->on_list) { |
157 | /* Initialize *lk and add it to lock_file_list: */ | |
158 | lk->fd = -1; | |
707103fd | 159 | lk->active = 0; |
04e57d4d | 160 | lk->owner = 0; |
6cad8053 | 161 | strbuf_init(&lk->filename, pathlen + LOCK_SUFFIX_LEN); |
04e57d4d MH |
162 | lk->next = lock_file_list; |
163 | lock_file_list = lk; | |
164 | lk->on_list = 1; | |
cf6950d3 MH |
165 | } else if (lk->filename.len) { |
166 | /* This shouldn't happen, but better safe than sorry. */ | |
167 | die("BUG: lock_file(\"%s\") called with improperly-reset lock_file object", | |
168 | path); | |
04e57d4d MH |
169 | } |
170 | ||
6cad8053 MH |
171 | strbuf_add(&lk->filename, path, pathlen); |
172 | if (!(flags & LOCK_NODEREF)) | |
173 | resolve_symlink(&lk->filename); | |
cf6950d3 MH |
174 | strbuf_addstr(&lk->filename, LOCK_SUFFIX); |
175 | lk->fd = open(lk->filename.buf, O_RDWR | O_CREAT | O_EXCL, 0666); | |
e31e949b | 176 | if (lk->fd < 0) { |
cf6950d3 | 177 | strbuf_reset(&lk->filename); |
e31e949b MH |
178 | return -1; |
179 | } | |
180 | lk->owner = getpid(); | |
707103fd | 181 | lk->active = 1; |
cf6950d3 | 182 | if (adjust_shared_perm(lk->filename.buf)) { |
e31e949b | 183 | int save_errno = errno; |
cf6950d3 | 184 | error("cannot fix permission bits on %s", lk->filename.buf); |
e31e949b MH |
185 | rollback_lock_file(lk); |
186 | errno = save_errno; | |
187 | return -1; | |
188 | } | |
4723ee99 | 189 | return lk->fd; |
021b6e45 JH |
190 | } |
191 | ||
6af926e8 | 192 | void unable_to_lock_message(const char *path, int err, struct strbuf *buf) |
e43a6fd3 | 193 | { |
bdfd739d | 194 | if (err == EEXIST) { |
6af926e8 | 195 | strbuf_addf(buf, "Unable to create '%s.lock': %s.\n\n" |
e43a6fd3 MM |
196 | "If no other git process is currently running, this probably means a\n" |
197 | "git process crashed in this repository earlier. Make sure no other git\n" | |
198 | "process is running and remove the file manually to continue.", | |
e2a57aac | 199 | absolute_path(path), strerror(err)); |
1b018fd9 | 200 | } else |
6af926e8 | 201 | strbuf_addf(buf, "Unable to create '%s.lock': %s", |
e2a57aac | 202 | absolute_path(path), strerror(err)); |
1b018fd9 MV |
203 | } |
204 | ||
205 | int unable_to_lock_error(const char *path, int err) | |
206 | { | |
6af926e8 RS |
207 | struct strbuf buf = STRBUF_INIT; |
208 | ||
209 | unable_to_lock_message(path, err, &buf); | |
210 | error("%s", buf.buf); | |
211 | strbuf_release(&buf); | |
1b018fd9 MV |
212 | return -1; |
213 | } | |
214 | ||
e197c218 | 215 | NORETURN void unable_to_lock_die(const char *path, int err) |
1b018fd9 | 216 | { |
6af926e8 RS |
217 | struct strbuf buf = STRBUF_INIT; |
218 | ||
219 | unable_to_lock_message(path, err, &buf); | |
220 | die("%s", buf.buf); | |
e43a6fd3 MM |
221 | } |
222 | ||
447ff1bf | 223 | /* This should return a meaningful errno on failure */ |
acd3b9ec | 224 | int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags) |
40aaae88 | 225 | { |
acd3b9ec JH |
226 | int fd = lock_file(lk, path, flags); |
227 | if (fd < 0 && (flags & LOCK_DIE_ON_ERROR)) | |
e197c218 | 228 | unable_to_lock_die(path, errno); |
40aaae88 JH |
229 | return fd; |
230 | } | |
231 | ||
acd3b9ec | 232 | int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags) |
ea3cd5c7 DB |
233 | { |
234 | int fd, orig_fd; | |
235 | ||
acd3b9ec | 236 | fd = lock_file(lk, path, flags); |
ea3cd5c7 | 237 | if (fd < 0) { |
acd3b9ec | 238 | if (flags & LOCK_DIE_ON_ERROR) |
e197c218 | 239 | unable_to_lock_die(path, errno); |
ea3cd5c7 DB |
240 | return fd; |
241 | } | |
242 | ||
243 | orig_fd = open(path, O_RDONLY); | |
244 | if (orig_fd < 0) { | |
245 | if (errno != ENOENT) { | |
acd3b9ec | 246 | if (flags & LOCK_DIE_ON_ERROR) |
ea3cd5c7 | 247 | die("cannot open '%s' for copying", path); |
ebb8e380 | 248 | rollback_lock_file(lk); |
ea3cd5c7 DB |
249 | return error("cannot open '%s' for copying", path); |
250 | } | |
251 | } else if (copy_fd(orig_fd, fd)) { | |
acd3b9ec | 252 | if (flags & LOCK_DIE_ON_ERROR) |
ea3cd5c7 | 253 | exit(128); |
ebb8e380 | 254 | rollback_lock_file(lk); |
ea3cd5c7 DB |
255 | return -1; |
256 | } | |
257 | return fd; | |
258 | } | |
259 | ||
d6cf61bf BC |
260 | int close_lock_file(struct lock_file *lk) |
261 | { | |
262 | int fd = lk->fd; | |
419f0c0f MH |
263 | |
264 | if (fd < 0) | |
265 | return 0; | |
266 | ||
d6cf61bf | 267 | lk->fd = -1; |
8e86c155 MH |
268 | if (close(fd)) { |
269 | int save_errno = errno; | |
270 | rollback_lock_file(lk); | |
271 | errno = save_errno; | |
272 | return -1; | |
273 | } | |
274 | return 0; | |
d6cf61bf BC |
275 | } |
276 | ||
93dcaea2 JH |
277 | int reopen_lock_file(struct lock_file *lk) |
278 | { | |
279 | if (0 <= lk->fd) | |
280 | die(_("BUG: reopen a lockfile that is still open")); | |
707103fd | 281 | if (!lk->active) |
93dcaea2 | 282 | die(_("BUG: reopen a lockfile that has been committed")); |
cf6950d3 | 283 | lk->fd = open(lk->filename.buf, O_WRONLY); |
93dcaea2 JH |
284 | return lk->fd; |
285 | } | |
286 | ||
021b6e45 JH |
287 | int commit_lock_file(struct lock_file *lk) |
288 | { | |
3e88e8fc MH |
289 | static struct strbuf result_file = STRBUF_INIT; |
290 | int err; | |
4f4713df | 291 | |
707103fd | 292 | if (!lk->active) |
8a1c7533 MH |
293 | die("BUG: attempt to commit unlocked object"); |
294 | ||
419f0c0f | 295 | if (close_lock_file(lk)) |
d6cf61bf | 296 | return -1; |
4f4713df | 297 | |
4f4713df | 298 | /* remove ".lock": */ |
cf6950d3 MH |
299 | strbuf_add(&result_file, lk->filename.buf, |
300 | lk->filename.len - LOCK_SUFFIX_LEN); | |
301 | err = rename(lk->filename.buf, result_file.buf); | |
3e88e8fc MH |
302 | strbuf_reset(&result_file); |
303 | if (err) { | |
1b1648f4 MH |
304 | int save_errno = errno; |
305 | rollback_lock_file(lk); | |
306 | errno = save_errno; | |
d6cf61bf | 307 | return -1; |
1b1648f4 MH |
308 | } |
309 | ||
707103fd | 310 | lk->active = 0; |
cf6950d3 | 311 | strbuf_reset(&lk->filename); |
d6cf61bf | 312 | return 0; |
021b6e45 JH |
313 | } |
314 | ||
30ca07a2 JH |
315 | int hold_locked_index(struct lock_file *lk, int die_on_error) |
316 | { | |
acd3b9ec JH |
317 | return hold_lock_file_for_update(lk, get_index_file(), |
318 | die_on_error | |
319 | ? LOCK_DIE_ON_ERROR | |
320 | : 0); | |
30ca07a2 JH |
321 | } |
322 | ||
021b6e45 JH |
323 | void rollback_lock_file(struct lock_file *lk) |
324 | { | |
707103fd | 325 | if (!lk->active) |
9085f8e2 MH |
326 | return; |
327 | ||
8e86c155 | 328 | if (!close_lock_file(lk)) { |
cf6950d3 | 329 | unlink_or_warn(lk->filename.buf); |
707103fd | 330 | lk->active = 0; |
cf6950d3 | 331 | strbuf_reset(&lk->filename); |
8e86c155 | 332 | } |
021b6e45 | 333 | } |