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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 | * | |
26 | * A lock_file object can be in several states: | |
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 | |
35 | * state, the lockfile exists, filename holds the filename of the | |
36 | * lockfile, fd holds a file descriptor open for writing to the | |
37 | * lockfile, and owner holds the PID of the process that locked the | |
38 | * file. | |
39 | * | |
40 | * - Locked, lockfile closed (after close_lock_file()). Same as the | |
41 | * previous state, except that the lockfile is closed and fd is -1. | |
42 | * | |
43 | * - Unlocked (after commit_lock_file(), rollback_lock_file(), or a | |
44 | * failed attempt to lock). In this state, filename[0] == '\0' and | |
45 | * fd is -1. The object is left registered in the lock_file_list, | |
46 | * and on_list is set. | |
47 | */ | |
48 | ||
021b6e45 JH |
49 | static struct lock_file *lock_file_list; |
50 | ||
51 | static void remove_lock_file(void) | |
52 | { | |
5e635e39 JH |
53 | pid_t me = getpid(); |
54 | ||
021b6e45 | 55 | while (lock_file_list) { |
5e635e39 | 56 | if (lock_file_list->owner == me && |
4723ee99 | 57 | lock_file_list->filename[0]) { |
d6cf61bf BC |
58 | if (lock_file_list->fd >= 0) |
59 | close(lock_file_list->fd); | |
691f1a28 | 60 | unlink_or_warn(lock_file_list->filename); |
4723ee99 | 61 | } |
021b6e45 JH |
62 | lock_file_list = lock_file_list->next; |
63 | } | |
64 | } | |
65 | ||
66 | static void remove_lock_file_on_signal(int signo) | |
67 | { | |
68 | remove_lock_file(); | |
4a16d072 | 69 | sigchain_pop(signo); |
021b6e45 JH |
70 | raise(signo); |
71 | } | |
72 | ||
5d5a7a67 BS |
73 | /* |
74 | * p = absolute or relative path name | |
75 | * | |
76 | * Return a pointer into p showing the beginning of the last path name | |
77 | * element. If p is empty or the root directory ("/"), just return p. | |
78 | */ | |
79 | static char *last_path_elm(char *p) | |
80 | { | |
81 | /* r starts pointing to null at the end of the string */ | |
82 | char *r = strchr(p, '\0'); | |
83 | ||
84 | if (r == p) | |
85 | return p; /* just return empty string */ | |
86 | ||
87 | r--; /* back up to last non-null character */ | |
88 | ||
89 | /* back up past trailing slashes, if any */ | |
90 | while (r > p && *r == '/') | |
91 | r--; | |
92 | ||
93 | /* | |
94 | * then go backwards until I hit a slash, or the beginning of | |
95 | * the string | |
96 | */ | |
97 | while (r > p && *(r-1) != '/') | |
98 | r--; | |
99 | return r; | |
100 | } | |
101 | ||
102 | ||
103 | /* We allow "recursive" symbolic links. Only within reason, though */ | |
104 | #define MAXDEPTH 5 | |
105 | ||
106 | /* | |
107 | * p = path that may be a symlink | |
108 | * s = full size of p | |
109 | * | |
110 | * If p is a symlink, attempt to overwrite p with a path to the real | |
111 | * file or directory (which may or may not exist), following a chain of | |
112 | * symlinks if necessary. Otherwise, leave p unmodified. | |
113 | * | |
114 | * This is a best-effort routine. If an error occurs, p will either be | |
115 | * left unmodified or will name a different symlink in a symlink chain | |
116 | * that started with p's initial contents. | |
117 | * | |
118 | * Always returns p. | |
119 | */ | |
120 | ||
121 | static char *resolve_symlink(char *p, size_t s) | |
122 | { | |
123 | int depth = MAXDEPTH; | |
124 | ||
125 | while (depth--) { | |
126 | char link[PATH_MAX]; | |
127 | int link_len = readlink(p, link, sizeof(link)); | |
128 | if (link_len < 0) { | |
129 | /* not a symlink anymore */ | |
130 | return p; | |
131 | } | |
132 | else if (link_len < sizeof(link)) | |
133 | /* readlink() never null-terminates */ | |
134 | link[link_len] = '\0'; | |
135 | else { | |
136 | warning("%s: symlink too long", p); | |
137 | return p; | |
138 | } | |
139 | ||
ecf4831d | 140 | if (is_absolute_path(link)) { |
5d5a7a67 BS |
141 | /* absolute path simply replaces p */ |
142 | if (link_len < s) | |
143 | strcpy(p, link); | |
144 | else { | |
145 | warning("%s: symlink too long", p); | |
146 | return p; | |
147 | } | |
148 | } else { | |
149 | /* | |
150 | * link is a relative path, so I must replace the | |
151 | * last element of p with it. | |
152 | */ | |
4b25d091 | 153 | char *r = (char *)last_path_elm(p); |
5d5a7a67 BS |
154 | if (r - p + link_len < s) |
155 | strcpy(r, link); | |
156 | else { | |
157 | warning("%s: symlink too long", p); | |
158 | return p; | |
159 | } | |
160 | } | |
161 | } | |
162 | return p; | |
163 | } | |
164 | ||
447ff1bf | 165 | /* Make sure errno contains a meaningful value on error */ |
acd3b9ec | 166 | static int lock_file(struct lock_file *lk, const char *path, int flags) |
021b6e45 | 167 | { |
5d5a7a67 | 168 | /* |
7108ad23 MH |
169 | * subtract LOCK_SUFFIX_LEN from size to make sure there's |
170 | * room for adding ".lock" for the lock file name: | |
5d5a7a67 | 171 | */ |
7108ad23 MH |
172 | static const size_t max_path_len = sizeof(lk->filename) - |
173 | LOCK_SUFFIX_LEN; | |
2fbd4f92 | 174 | |
04e57d4d MH |
175 | if (!lock_file_list) { |
176 | /* One-time initialization */ | |
177 | sigchain_push_common(remove_lock_file_on_signal); | |
178 | atexit(remove_lock_file); | |
179 | } | |
180 | ||
181 | if (!lk->on_list) { | |
182 | /* Initialize *lk and add it to lock_file_list: */ | |
183 | lk->fd = -1; | |
184 | lk->owner = 0; | |
185 | lk->filename[0] = 0; | |
186 | lk->next = lock_file_list; | |
187 | lock_file_list = lk; | |
188 | lk->on_list = 1; | |
189 | } | |
190 | ||
447ff1bf RS |
191 | if (strlen(path) >= max_path_len) { |
192 | errno = ENAMETOOLONG; | |
2fbd4f92 | 193 | return -1; |
447ff1bf | 194 | } |
2fbd4f92 | 195 | strcpy(lk->filename, path); |
acd3b9ec | 196 | if (!(flags & LOCK_NODEREF)) |
2fbd4f92 | 197 | resolve_symlink(lk->filename, max_path_len); |
7108ad23 | 198 | strcat(lk->filename, LOCK_SUFFIX); |
4723ee99 JS |
199 | lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666); |
200 | if (0 <= lk->fd) { | |
5e635e39 | 201 | lk->owner = getpid(); |
447ff1bf RS |
202 | if (adjust_shared_perm(lk->filename)) { |
203 | int save_errno = errno; | |
204 | error("cannot fix permission bits on %s", | |
205 | lk->filename); | |
41dd4ffa | 206 | rollback_lock_file(lk); |
447ff1bf RS |
207 | errno = save_errno; |
208 | return -1; | |
209 | } | |
021b6e45 | 210 | } |
1084b845 JH |
211 | else |
212 | lk->filename[0] = 0; | |
4723ee99 | 213 | return lk->fd; |
021b6e45 JH |
214 | } |
215 | ||
6af926e8 | 216 | void unable_to_lock_message(const char *path, int err, struct strbuf *buf) |
e43a6fd3 | 217 | { |
bdfd739d | 218 | if (err == EEXIST) { |
6af926e8 | 219 | strbuf_addf(buf, "Unable to create '%s.lock': %s.\n\n" |
e43a6fd3 MM |
220 | "If no other git process is currently running, this probably means a\n" |
221 | "git process crashed in this repository earlier. Make sure no other git\n" | |
222 | "process is running and remove the file manually to continue.", | |
e2a57aac | 223 | absolute_path(path), strerror(err)); |
1b018fd9 | 224 | } else |
6af926e8 | 225 | strbuf_addf(buf, "Unable to create '%s.lock': %s", |
e2a57aac | 226 | absolute_path(path), strerror(err)); |
1b018fd9 MV |
227 | } |
228 | ||
229 | int unable_to_lock_error(const char *path, int err) | |
230 | { | |
6af926e8 RS |
231 | struct strbuf buf = STRBUF_INIT; |
232 | ||
233 | unable_to_lock_message(path, err, &buf); | |
234 | error("%s", buf.buf); | |
235 | strbuf_release(&buf); | |
1b018fd9 MV |
236 | return -1; |
237 | } | |
238 | ||
e197c218 | 239 | NORETURN void unable_to_lock_die(const char *path, int err) |
1b018fd9 | 240 | { |
6af926e8 RS |
241 | struct strbuf buf = STRBUF_INIT; |
242 | ||
243 | unable_to_lock_message(path, err, &buf); | |
244 | die("%s", buf.buf); | |
e43a6fd3 MM |
245 | } |
246 | ||
447ff1bf | 247 | /* This should return a meaningful errno on failure */ |
acd3b9ec | 248 | int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags) |
40aaae88 | 249 | { |
acd3b9ec JH |
250 | int fd = lock_file(lk, path, flags); |
251 | if (fd < 0 && (flags & LOCK_DIE_ON_ERROR)) | |
e197c218 | 252 | unable_to_lock_die(path, errno); |
40aaae88 JH |
253 | return fd; |
254 | } | |
255 | ||
acd3b9ec | 256 | int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags) |
ea3cd5c7 DB |
257 | { |
258 | int fd, orig_fd; | |
259 | ||
acd3b9ec | 260 | fd = lock_file(lk, path, flags); |
ea3cd5c7 | 261 | if (fd < 0) { |
acd3b9ec | 262 | if (flags & LOCK_DIE_ON_ERROR) |
e197c218 | 263 | unable_to_lock_die(path, errno); |
ea3cd5c7 DB |
264 | return fd; |
265 | } | |
266 | ||
267 | orig_fd = open(path, O_RDONLY); | |
268 | if (orig_fd < 0) { | |
269 | if (errno != ENOENT) { | |
acd3b9ec | 270 | if (flags & LOCK_DIE_ON_ERROR) |
ea3cd5c7 | 271 | die("cannot open '%s' for copying", path); |
ebb8e380 | 272 | rollback_lock_file(lk); |
ea3cd5c7 DB |
273 | return error("cannot open '%s' for copying", path); |
274 | } | |
275 | } else if (copy_fd(orig_fd, fd)) { | |
acd3b9ec | 276 | if (flags & LOCK_DIE_ON_ERROR) |
ea3cd5c7 | 277 | exit(128); |
ebb8e380 | 278 | rollback_lock_file(lk); |
ea3cd5c7 DB |
279 | return -1; |
280 | } | |
281 | return fd; | |
282 | } | |
283 | ||
d6cf61bf BC |
284 | int close_lock_file(struct lock_file *lk) |
285 | { | |
286 | int fd = lk->fd; | |
419f0c0f MH |
287 | |
288 | if (fd < 0) | |
289 | return 0; | |
290 | ||
d6cf61bf BC |
291 | lk->fd = -1; |
292 | return close(fd); | |
293 | } | |
294 | ||
93dcaea2 JH |
295 | int reopen_lock_file(struct lock_file *lk) |
296 | { | |
297 | if (0 <= lk->fd) | |
298 | die(_("BUG: reopen a lockfile that is still open")); | |
299 | if (!lk->filename[0]) | |
300 | die(_("BUG: reopen a lockfile that has been committed")); | |
301 | lk->fd = open(lk->filename, O_WRONLY); | |
302 | return lk->fd; | |
303 | } | |
304 | ||
021b6e45 JH |
305 | int commit_lock_file(struct lock_file *lk) |
306 | { | |
307 | char result_file[PATH_MAX]; | |
d6cf61bf | 308 | size_t i; |
419f0c0f | 309 | if (close_lock_file(lk)) |
d6cf61bf | 310 | return -1; |
021b6e45 | 311 | strcpy(result_file, lk->filename); |
7108ad23 | 312 | i = strlen(result_file) - LOCK_SUFFIX_LEN; /* .lock */ |
021b6e45 | 313 | result_file[i] = 0; |
d6cf61bf BC |
314 | if (rename(lk->filename, result_file)) |
315 | return -1; | |
021b6e45 | 316 | lk->filename[0] = 0; |
d6cf61bf | 317 | return 0; |
021b6e45 JH |
318 | } |
319 | ||
30ca07a2 JH |
320 | int hold_locked_index(struct lock_file *lk, int die_on_error) |
321 | { | |
acd3b9ec JH |
322 | return hold_lock_file_for_update(lk, get_index_file(), |
323 | die_on_error | |
324 | ? LOCK_DIE_ON_ERROR | |
325 | : 0); | |
30ca07a2 JH |
326 | } |
327 | ||
021b6e45 JH |
328 | void rollback_lock_file(struct lock_file *lk) |
329 | { | |
9085f8e2 MH |
330 | if (!lk->filename[0]) |
331 | return; | |
332 | ||
26f5d3b6 | 333 | close_lock_file(lk); |
9085f8e2 MH |
334 | unlink_or_warn(lk->filename); |
335 | lk->filename[0] = 0; | |
021b6e45 | 336 | } |