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1 | /* | |
2 | * Copyright (c) 2005, Junio C Hamano | |
3 | */ | |
4 | #include "cache.h" | |
5 | #include "sigchain.h" | |
6 | ||
7 | static struct lock_file *lock_file_list; | |
8 | static const char *alternate_index_output; | |
9 | ||
10 | static void remove_lock_file(void) | |
11 | { | |
12 | pid_t me = getpid(); | |
13 | ||
14 | while (lock_file_list) { | |
15 | if (lock_file_list->owner == me && | |
16 | lock_file_list->filename[0]) { | |
17 | if (lock_file_list->fd >= 0) | |
18 | close(lock_file_list->fd); | |
19 | unlink_or_warn(lock_file_list->filename); | |
20 | } | |
21 | lock_file_list = lock_file_list->next; | |
22 | } | |
23 | } | |
24 | ||
25 | static void remove_lock_file_on_signal(int signo) | |
26 | { | |
27 | remove_lock_file(); | |
28 | sigchain_pop(signo); | |
29 | raise(signo); | |
30 | } | |
31 | ||
32 | /* | |
33 | * p = absolute or relative path name | |
34 | * | |
35 | * Return a pointer into p showing the beginning of the last path name | |
36 | * element. If p is empty or the root directory ("/"), just return p. | |
37 | */ | |
38 | static char *last_path_elm(char *p) | |
39 | { | |
40 | /* r starts pointing to null at the end of the string */ | |
41 | char *r = strchr(p, '\0'); | |
42 | ||
43 | if (r == p) | |
44 | return p; /* just return empty string */ | |
45 | ||
46 | r--; /* back up to last non-null character */ | |
47 | ||
48 | /* back up past trailing slashes, if any */ | |
49 | while (r > p && *r == '/') | |
50 | r--; | |
51 | ||
52 | /* | |
53 | * then go backwards until I hit a slash, or the beginning of | |
54 | * the string | |
55 | */ | |
56 | while (r > p && *(r-1) != '/') | |
57 | r--; | |
58 | return r; | |
59 | } | |
60 | ||
61 | ||
62 | /* We allow "recursive" symbolic links. Only within reason, though */ | |
63 | #define MAXDEPTH 5 | |
64 | ||
65 | /* | |
66 | * p = path that may be a symlink | |
67 | * s = full size of p | |
68 | * | |
69 | * If p is a symlink, attempt to overwrite p with a path to the real | |
70 | * file or directory (which may or may not exist), following a chain of | |
71 | * symlinks if necessary. Otherwise, leave p unmodified. | |
72 | * | |
73 | * This is a best-effort routine. If an error occurs, p will either be | |
74 | * left unmodified or will name a different symlink in a symlink chain | |
75 | * that started with p's initial contents. | |
76 | * | |
77 | * Always returns p. | |
78 | */ | |
79 | ||
80 | static char *resolve_symlink(char *p, size_t s) | |
81 | { | |
82 | int depth = MAXDEPTH; | |
83 | ||
84 | while (depth--) { | |
85 | char link[PATH_MAX]; | |
86 | int link_len = readlink(p, link, sizeof(link)); | |
87 | if (link_len < 0) { | |
88 | /* not a symlink anymore */ | |
89 | return p; | |
90 | } | |
91 | else if (link_len < sizeof(link)) | |
92 | /* readlink() never null-terminates */ | |
93 | link[link_len] = '\0'; | |
94 | else { | |
95 | warning("%s: symlink too long", p); | |
96 | return p; | |
97 | } | |
98 | ||
99 | if (is_absolute_path(link)) { | |
100 | /* absolute path simply replaces p */ | |
101 | if (link_len < s) | |
102 | strcpy(p, link); | |
103 | else { | |
104 | warning("%s: symlink too long", p); | |
105 | return p; | |
106 | } | |
107 | } else { | |
108 | /* | |
109 | * link is a relative path, so I must replace the | |
110 | * last element of p with it. | |
111 | */ | |
112 | char *r = (char *)last_path_elm(p); | |
113 | if (r - p + link_len < s) | |
114 | strcpy(r, link); | |
115 | else { | |
116 | warning("%s: symlink too long", p); | |
117 | return p; | |
118 | } | |
119 | } | |
120 | } | |
121 | return p; | |
122 | } | |
123 | ||
124 | ||
125 | static int lock_file(struct lock_file *lk, const char *path, int flags) | |
126 | { | |
127 | if (strlen(path) >= sizeof(lk->filename)) | |
128 | return -1; | |
129 | strcpy(lk->filename, path); | |
130 | /* | |
131 | * subtract 5 from size to make sure there's room for adding | |
132 | * ".lock" for the lock file name | |
133 | */ | |
134 | if (!(flags & LOCK_NODEREF)) | |
135 | resolve_symlink(lk->filename, sizeof(lk->filename)-5); | |
136 | strcat(lk->filename, ".lock"); | |
137 | lk->fd = open(lk->filename, O_RDWR | O_CREAT | O_EXCL, 0666); | |
138 | if (0 <= lk->fd) { | |
139 | if (!lock_file_list) { | |
140 | sigchain_push_common(remove_lock_file_on_signal); | |
141 | atexit(remove_lock_file); | |
142 | } | |
143 | lk->owner = getpid(); | |
144 | if (!lk->on_list) { | |
145 | lk->next = lock_file_list; | |
146 | lock_file_list = lk; | |
147 | lk->on_list = 1; | |
148 | } | |
149 | if (adjust_shared_perm(lk->filename)) | |
150 | return error("cannot fix permission bits on %s", | |
151 | lk->filename); | |
152 | } | |
153 | else | |
154 | lk->filename[0] = 0; | |
155 | return lk->fd; | |
156 | } | |
157 | ||
158 | static char *unable_to_lock_message(const char *path, int err) | |
159 | { | |
160 | struct strbuf buf = STRBUF_INIT; | |
161 | ||
162 | if (err == EEXIST) { | |
163 | strbuf_addf(&buf, "Unable to create '%s.lock': %s.\n\n" | |
164 | "If no other git process is currently running, this probably means a\n" | |
165 | "git process crashed in this repository earlier. Make sure no other git\n" | |
166 | "process is running and remove the file manually to continue.", | |
167 | absolute_path(path), strerror(err)); | |
168 | } else | |
169 | strbuf_addf(&buf, "Unable to create '%s.lock': %s", | |
170 | absolute_path(path), strerror(err)); | |
171 | return strbuf_detach(&buf, NULL); | |
172 | } | |
173 | ||
174 | int unable_to_lock_error(const char *path, int err) | |
175 | { | |
176 | char *msg = unable_to_lock_message(path, err); | |
177 | error("%s", msg); | |
178 | free(msg); | |
179 | return -1; | |
180 | } | |
181 | ||
182 | NORETURN void unable_to_lock_index_die(const char *path, int err) | |
183 | { | |
184 | die("%s", unable_to_lock_message(path, err)); | |
185 | } | |
186 | ||
187 | int hold_lock_file_for_update(struct lock_file *lk, const char *path, int flags) | |
188 | { | |
189 | int fd = lock_file(lk, path, flags); | |
190 | if (fd < 0 && (flags & LOCK_DIE_ON_ERROR)) | |
191 | unable_to_lock_index_die(path, errno); | |
192 | return fd; | |
193 | } | |
194 | ||
195 | int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags) | |
196 | { | |
197 | int fd, orig_fd; | |
198 | ||
199 | fd = lock_file(lk, path, flags); | |
200 | if (fd < 0) { | |
201 | if (flags & LOCK_DIE_ON_ERROR) | |
202 | unable_to_lock_index_die(path, errno); | |
203 | return fd; | |
204 | } | |
205 | ||
206 | orig_fd = open(path, O_RDONLY); | |
207 | if (orig_fd < 0) { | |
208 | if (errno != ENOENT) { | |
209 | if (flags & LOCK_DIE_ON_ERROR) | |
210 | die("cannot open '%s' for copying", path); | |
211 | close(fd); | |
212 | return error("cannot open '%s' for copying", path); | |
213 | } | |
214 | } else if (copy_fd(orig_fd, fd)) { | |
215 | if (flags & LOCK_DIE_ON_ERROR) | |
216 | exit(128); | |
217 | close(fd); | |
218 | return -1; | |
219 | } | |
220 | return fd; | |
221 | } | |
222 | ||
223 | int close_lock_file(struct lock_file *lk) | |
224 | { | |
225 | int fd = lk->fd; | |
226 | lk->fd = -1; | |
227 | return close(fd); | |
228 | } | |
229 | ||
230 | int commit_lock_file(struct lock_file *lk) | |
231 | { | |
232 | char result_file[PATH_MAX]; | |
233 | size_t i; | |
234 | if (lk->fd >= 0 && close_lock_file(lk)) | |
235 | return -1; | |
236 | strcpy(result_file, lk->filename); | |
237 | i = strlen(result_file) - 5; /* .lock */ | |
238 | result_file[i] = 0; | |
239 | if (rename(lk->filename, result_file)) | |
240 | return -1; | |
241 | lk->filename[0] = 0; | |
242 | return 0; | |
243 | } | |
244 | ||
245 | int hold_locked_index(struct lock_file *lk, int die_on_error) | |
246 | { | |
247 | return hold_lock_file_for_update(lk, get_index_file(), | |
248 | die_on_error | |
249 | ? LOCK_DIE_ON_ERROR | |
250 | : 0); | |
251 | } | |
252 | ||
253 | void set_alternate_index_output(const char *name) | |
254 | { | |
255 | alternate_index_output = name; | |
256 | } | |
257 | ||
258 | int commit_locked_index(struct lock_file *lk) | |
259 | { | |
260 | if (alternate_index_output) { | |
261 | if (lk->fd >= 0 && close_lock_file(lk)) | |
262 | return -1; | |
263 | if (rename(lk->filename, alternate_index_output)) | |
264 | return -1; | |
265 | lk->filename[0] = 0; | |
266 | return 0; | |
267 | } | |
268 | else | |
269 | return commit_lock_file(lk); | |
270 | } | |
271 | ||
272 | void rollback_lock_file(struct lock_file *lk) | |
273 | { | |
274 | if (lk->filename[0]) { | |
275 | if (lk->fd >= 0) | |
276 | close(lk->fd); | |
277 | unlink_or_warn(lk->filename); | |
278 | } | |
279 | lk->filename[0] = 0; | |
280 | } |