1 #include "cache.h"
3 /*
4 * Returns the length (on a path component basis) of the longest
5 * common prefix match of 'name_a' and 'name_b'.
6 */
7 static int longest_path_match(const char *name_a, int len_a,
8 const char *name_b, int len_b,
9 int *previous_slash)
10 {
11 int max_len, match_len = 0, match_len_prev = 0, i = 0;
13 max_len = len_a < len_b ? len_a : len_b;
14 while (i < max_len && name_a[i] == name_b[i]) {
15 if (name_a[i] == '/') {
16 match_len_prev = match_len;
17 match_len = i;
18 }
19 i++;
20 }
21 /*
22 * Is 'name_b' a substring of 'name_a', the other way around,
23 * or is 'name_a' and 'name_b' the exact same string?
24 */
25 if (i >= max_len && ((len_a > len_b && name_a[len_b] == '/') ||
26 (len_a < len_b && name_b[len_a] == '/') ||
27 (len_a == len_b))) {
28 match_len_prev = match_len;
29 match_len = i;
30 }
31 *previous_slash = match_len_prev;
32 return match_len;
33 }
35 static struct cache_def {
36 char path[PATH_MAX + 1];
37 int len;
38 int flags;
39 int track_flags;
40 int prefix_len_stat_func;
41 } cache;
43 static inline void reset_lstat_cache(void)
44 {
45 cache.path[0] = '\0';
46 cache.len = 0;
47 cache.flags = 0;
48 /*
49 * The track_flags and prefix_len_stat_func members is only
50 * set by the safeguard rule inside lstat_cache()
51 */
52 }
54 #define SWITCHES_BEFORE_WARNING 10
55 static unsigned int cache_switches, number_of_warnings;
56 static unsigned int current_cache_func, last_cache_func;
57 static unsigned int total_calls;
59 #define FL_DIR (1 << 0)
60 #define FL_NOENT (1 << 1)
61 #define FL_SYMLINK (1 << 2)
62 #define FL_LSTATERR (1 << 3)
63 #define FL_ERR (1 << 4)
64 #define FL_FULLPATH (1 << 5)
66 /*
67 * Check if name 'name' of length 'len' has a symlink leading
68 * component, or if the directory exists and is real, or not.
69 *
70 * To speed up the check, some information is allowed to be cached.
71 * This can be indicated by the 'track_flags' argument, which also can
72 * be used to indicate that we should check the full path.
73 *
74 * The 'prefix_len_stat_func' parameter can be used to set the length
75 * of the prefix, where the cache should use the stat() function
76 * instead of the lstat() function to test each path component.
77 */
78 static int lstat_cache(const char *name, int len,
79 int track_flags, int prefix_len_stat_func)
80 {
81 int match_len, last_slash, last_slash_dir, previous_slash;
82 int match_flags, ret_flags, save_flags, max_len, ret;
83 struct stat st;
85 total_calls++;
86 if (cache.track_flags != track_flags ||
87 cache.prefix_len_stat_func != prefix_len_stat_func) {
88 /*
89 * As a safeguard rule we clear the cache if the
90 * values of track_flags and/or prefix_len_stat_func
91 * does not match with the last supplied values.
92 */
93 reset_lstat_cache();
94 cache.track_flags = track_flags;
95 cache.prefix_len_stat_func = prefix_len_stat_func;
96 match_len = last_slash = 0;
97 cache_switches++;
98 if (cache_switches > SWITCHES_BEFORE_WARNING) {
99 if (number_of_warnings < 10 || number_of_warnings % 1000 == 0)
100 printf("warning from %s:%d cache_switches:%u > %u "\
101 "(current:%u last:%u total:%u)\n",
102 __FILE__, __LINE__,
103 cache_switches, SWITCHES_BEFORE_WARNING,
104 current_cache_func, last_cache_func,
105 total_calls);
106 number_of_warnings++;
107 }
108 } else {
109 /*
110 * Check to see if we have a match from the cache for
111 * the 2 "excluding" path types.
112 */
113 match_len = last_slash =
114 longest_path_match(name, len, cache.path, cache.len,
115 &previous_slash);
116 match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
117 if (match_flags && match_len == cache.len)
118 return match_flags;
119 /*
120 * If we now have match_len > 0, we would know that
121 * the matched part will always be a directory.
122 *
123 * Also, if we are tracking directories and 'name' is
124 * a substring of the cache on a path component basis,
125 * we can return immediately.
126 */
127 match_flags = track_flags & FL_DIR;
128 if (match_flags && len == match_len)
129 return match_flags;
130 }
132 /*
133 * Okay, no match from the cache so far, so now we have to
134 * check the rest of the path components.
135 */
136 ret_flags = FL_DIR;
137 last_slash_dir = last_slash;
138 max_len = len < PATH_MAX ? len : PATH_MAX;
139 while (match_len < max_len) {
140 do {
141 cache.path[match_len] = name[match_len];
142 match_len++;
143 } while (match_len < max_len && name[match_len] != '/');
144 if (match_len >= max_len && !(track_flags & FL_FULLPATH))
145 break;
146 last_slash = match_len;
147 cache.path[last_slash] = '\0';
149 if (last_slash <= prefix_len_stat_func)
150 ret = stat(cache.path, &st);
151 else
152 ret = lstat(cache.path, &st);
154 if (ret) {
155 ret_flags = FL_LSTATERR;
156 if (errno == ENOENT)
157 ret_flags |= FL_NOENT;
158 } else if (S_ISDIR(st.st_mode)) {
159 last_slash_dir = last_slash;
160 continue;
161 } else if (S_ISLNK(st.st_mode)) {
162 ret_flags = FL_SYMLINK;
163 } else {
164 ret_flags = FL_ERR;
165 }
166 break;
167 }
169 /*
170 * At the end update the cache. Note that max 3 different
171 * path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
172 * for the moment!
173 */
174 save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
175 if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
176 cache.path[last_slash] = '\0';
177 cache.len = last_slash;
178 cache.flags = save_flags;
179 } else if ((track_flags & FL_DIR) &&
180 last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
181 /*
182 * We have a separate test for the directory case,
183 * since it could be that we have found a symlink or a
184 * non-existing directory and the track_flags says
185 * that we cannot cache this fact, so the cache would
186 * then have been left empty in this case.
187 *
188 * But if we are allowed to track real directories, we
189 * can still cache the path components before the last
190 * one (the found symlink or non-existing component).
191 */
192 cache.path[last_slash_dir] = '\0';
193 cache.len = last_slash_dir;
194 cache.flags = FL_DIR;
195 } else {
196 reset_lstat_cache();
197 }
198 return ret_flags;
199 }
201 /*
202 * Invalidate the given 'name' from the cache, if 'name' matches
203 * completely with the cache.
204 */
205 void invalidate_lstat_cache(const char *name, int len)
206 {
207 int match_len, previous_slash;
209 match_len = longest_path_match(name, len, cache.path, cache.len,
210 &previous_slash);
211 if (len == match_len) {
212 if ((cache.track_flags & FL_DIR) && previous_slash > 0) {
213 cache.path[previous_slash] = '\0';
214 cache.len = previous_slash;
215 cache.flags = FL_DIR;
216 } else
217 reset_lstat_cache();
218 }
219 }
221 /*
222 * Completely clear the contents of the cache
223 */
224 void clear_lstat_cache(void)
225 {
226 reset_lstat_cache();
227 }
229 #define USE_ONLY_LSTAT 0
231 /*
232 * Return non-zero if path 'name' has a leading symlink component
233 */
234 int has_symlink_leading_path(const char *name, int len)
235 {
236 last_cache_func = current_cache_func;
237 current_cache_func = 1;
238 return lstat_cache(name, len,
239 FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
240 FL_SYMLINK;
241 }
243 /*
244 * Return non-zero if path 'name' has a leading symlink component or
245 * if some leading path component does not exists.
246 */
247 int has_symlink_or_noent_leading_path(const char *name, int len)
248 {
249 last_cache_func = current_cache_func;
250 current_cache_func = 2;
251 return lstat_cache(name, len,
252 FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
253 (FL_SYMLINK|FL_NOENT);
254 }
256 /*
257 * Return non-zero if all path components of 'name' exists as a
258 * directory. If prefix_len > 0, we will test with the stat()
259 * function instead of the lstat() function for a prefix length of
260 * 'prefix_len', thus we then allow for symlinks in the prefix part as
261 * long as those points to real existing directories.
262 */
263 int has_dirs_only_path(const char *name, int len, int prefix_len)
264 {
265 last_cache_func = current_cache_func;
266 current_cache_func = 3;
267 return lstat_cache(name, len,
268 FL_DIR|FL_FULLPATH, prefix_len) &
269 FL_DIR;
270 }
272 static struct removal_def {
273 char path[PATH_MAX];
274 int len;
275 } removal;
277 static void do_remove_scheduled_dirs(int new_len)
278 {
279 while (removal.len > new_len) {
280 removal.path[removal.len] = '\0';
281 if (rmdir(removal.path))
282 break;
283 do {
284 removal.len--;
285 } while (removal.len > new_len &&
286 removal.path[removal.len] != '/');
287 }
288 removal.len = new_len;
289 return;
290 }
292 void schedule_dir_for_removal(const char *name, int len)
293 {
294 int match_len, last_slash, i, previous_slash;
296 match_len = last_slash = i =
297 longest_path_match(name, len, removal.path, removal.len,
298 &previous_slash);
299 /* Find last slash inside 'name' */
300 while (i < len) {
301 if (name[i] == '/')
302 last_slash = i;
303 i++;
304 }
306 /*
307 * If we are about to go down the directory tree, we check if
308 * we must first go upwards the tree, such that we then can
309 * remove possible empty directories as we go upwards.
310 */
311 if (match_len < last_slash && match_len < removal.len)
312 do_remove_scheduled_dirs(match_len);
313 /*
314 * If we go deeper down the directory tree, we only need to
315 * save the new path components as we go down.
316 */
317 if (match_len < last_slash) {
318 memcpy(&removal.path[match_len], &name[match_len],
319 last_slash - match_len);
320 removal.len = last_slash;
321 }
322 return;
323 }
325 void remove_scheduled_dirs(void)
326 {
327 do_remove_scheduled_dirs(0);
328 return;
329 }