1/*
2 * Copyright (c) 2005, Junio C Hamano
3 */
4#include "cache.h"
5#include "sigchain.h"
6static struct lock_file *lock_file_list;
8static const char *alternate_index_output;
9static void remove_lock_file(void)
11{
12 pid_t me = getpid();
13 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}
24static void remove_lock_file_on_signal(int signo)
26{
27 remove_lock_file();
28 sigchain_pop(signo);
29 raise(signo);
30}
31/*
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 */
38static 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 if (r == p)
44 return p; /* just return empty string */
45 r--; /* back up to last non-null character */
47 /* back up past trailing slashes, if any */
49 while (r > p && *r == '/')
50 r--;
51 /*
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/* We allow "recursive" symbolic links. Only within reason, though */
63#define MAXDEPTH 5
64/*
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 */
79static char *resolve_symlink(char *p, size_t s)
81{
82 int depth = MAXDEPTH;
83 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 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}
123static 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}
157static char *unable_to_lock_message(const char *path, int err)
159{
160 struct strbuf buf = STRBUF_INIT;
161 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}
173int 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}
181NORETURN void unable_to_lock_index_die(const char *path, int err)
183{
184 die("%s", unable_to_lock_message(path, err));
185}
186int 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}
194int hold_lock_file_for_append(struct lock_file *lk, const char *path, int flags)
196{
197 int fd, orig_fd;
198 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 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}
222int close_lock_file(struct lock_file *lk)
224{
225 int fd = lk->fd;
226 lk->fd = -1;
227 return close(fd);
228}
229int 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}
244int 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}
252void set_alternate_index_output(const char *name)
254{
255 alternate_index_output = name;
256}
257int 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}
271void 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}