lib: rename include dir to babeltrace2
[babeltrace.git] / fd-cache / fd-cache.c
1 /*
2 * fd-cache.c
3 *
4 * Babeltrace - File descriptor cache
5 *
6 * Copyright 2019 Francis Deslauriers <francis.deslauriers@efficios.com>
7 *
8 * Author: Francis Deslauriers <francis.deslauriers@efficios.com>
9 *
10 * Permission is hereby granted, free of charge, to any person obtaining a copy
11 * of this software and associated documentation files (the "Software"), to deal
12 * in the Software without restriction, including without limitation the rights
13 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
14 * copies of the Software, and to permit persons to whom the Software is
15 * furnished to do so, subject to the following conditions:
16 *
17 * The above copyright notice and this permission notice shall be included in
18 * all copies or substantial portions of the Software.
19 *
20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
23 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
24 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
25 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
26 * SOFTWARE.
27 */
28
29 #define BT_LOG_TAG "FD-CACHE"
30 #include "logging.h"
31
32 #include <fcntl.h>
33 #include <sys/stat.h>
34 #include <sys/types.h>
35 #include <unistd.h>
36 #include <glib.h>
37
38 #include <babeltrace2/assert-internal.h>
39 #include <babeltrace2/fd-cache-internal.h>
40
41 struct file_key {
42 uint64_t dev;
43 uint64_t ino;
44 };
45
46 struct fd_handle_internal {
47 struct bt_fd_cache_handle fd_handle;
48 uint64_t ref_count;
49 struct file_key *key;
50 };
51
52 static
53 void fd_cache_handle_internal_destroy(
54 struct fd_handle_internal *internal_fd)
55 {
56 if (!internal_fd) {
57 goto end;
58 }
59
60 if (internal_fd->fd_handle.fd >= 0) {
61 close(internal_fd->fd_handle.fd);
62 internal_fd->fd_handle.fd = -1;
63 }
64
65 end:
66 g_free(internal_fd);
67 }
68
69 /*
70 * Using simple hash algorithm found on stackoverflow:
71 * https://stackoverflow.com/questions/664014/
72 */
73 static inline
74 uint64_t hash_uint64_t(uint64_t x) {
75 x = (x ^ (x >> 30)) * UINT64_C(0xbf58476d1ce4e5b9);
76 x = (x ^ (x >> 27)) * UINT64_C(0x94d049bb133111eb);
77 x = x ^ (x >> 31);
78 return x;
79 }
80
81 static
82 guint file_key_hash(gconstpointer v)
83 {
84 const struct file_key *fk = v;
85 return hash_uint64_t(fk->dev) ^ hash_uint64_t(fk->ino);
86 }
87
88 static
89 gboolean file_key_equal(gconstpointer v1, gconstpointer v2)
90 {
91 const struct file_key *fk1 = v1;
92 const struct file_key *fk2 = v2;
93
94 return (fk1->dev == fk2->dev) && (fk1->ino == fk2->ino);
95 }
96
97 static
98 void file_key_destroy(gpointer data)
99 {
100 struct file_key *fk = data;
101 g_free(fk);
102 }
103
104 BT_HIDDEN
105 int bt_fd_cache_init(struct bt_fd_cache *fdc)
106 {
107 int ret = 0;
108
109 fdc->cache = g_hash_table_new_full(file_key_hash, file_key_equal,
110 file_key_destroy, (GDestroyNotify) fd_cache_handle_internal_destroy);
111 if (!fdc->cache) {
112 ret = -1;
113 }
114
115 return ret;
116 }
117
118 BT_HIDDEN
119 void bt_fd_cache_fini(struct bt_fd_cache *fdc)
120 {
121 BT_ASSERT(fdc->cache);
122 /*
123 * All handle should have been removed for the hashtable at this point.
124 */
125 BT_ASSERT(g_hash_table_size(fdc->cache) == 0);
126 g_hash_table_destroy(fdc->cache);
127
128 return;
129 }
130
131 BT_HIDDEN
132 struct bt_fd_cache_handle *bt_fd_cache_get_handle(struct bt_fd_cache *fdc,
133 const char *path)
134 {
135 struct fd_handle_internal *fd_internal = NULL;
136 struct stat statbuf;
137 struct file_key fk;
138 int ret, fd = -1;
139
140 ret = stat(path, &statbuf);
141 if (ret < 0) {
142 /*
143 * This is not necessarily an error as we sometimes try to open
144 * files to see if they exist. Log the error as DEBUG severity
145 * level.
146 */
147 BT_LOGD_ERRNO("Failed to stat file", ": path=%s", path);
148 goto end;
149 }
150
151 /*
152 * Use the device number and inode number to uniquely identify a file.
153 * Even if the file has the same path, it may have been replaced so we
154 * must open a new FD for it. This replacement of file is more likely
155 * to happen with a lttng-live source component.
156 */
157 fk.dev = statbuf.st_dev;
158 fk.ino = statbuf.st_ino;
159
160 fd_internal = g_hash_table_lookup(fdc->cache, &fk);
161 if (!fd_internal) {
162 struct file_key *file_key;
163
164 fd = open(path, O_RDONLY);
165 if (fd < 0) {
166 BT_LOGE_ERRNO("Failed to open file", "path=%s", path);
167 goto error;
168 }
169
170 fd_internal = g_new0(struct fd_handle_internal, 1);
171 if (!fd_internal) {
172 BT_LOGE("Failed to allocate fd internal handle");
173 goto error;
174 }
175
176 file_key = g_new0(struct file_key, 1);
177 if (!fd_internal) {
178 BT_LOGE("Failed to allocate file key");
179 goto error;
180 }
181
182 *file_key = fk;
183
184 fd_internal->fd_handle.fd = fd;
185 fd_internal->ref_count = 0;
186 fd_internal->key = file_key;
187
188 /* Insert the newly created fd handle. */
189 g_hash_table_insert(fdc->cache, fd_internal->key, fd_internal);
190 }
191
192 fd_internal->ref_count++;
193 goto end;
194
195 error:
196 /*
197 * Close file descriptor if it was open() and we are currently on error
198 * path.
199 */
200 if (fd != -1) {
201 ret = close(fd);
202 if (ret) {
203 BT_LOGE_ERRNO("Failed to close file descriptor",
204 ": fd=%i, path=%s", fd, path);
205 }
206 }
207
208 fd_cache_handle_internal_destroy(fd_internal);
209 fd_internal = NULL;
210 end:
211 return (struct bt_fd_cache_handle *) fd_internal;
212 }
213
214 BT_HIDDEN
215 void bt_fd_cache_put_handle(struct bt_fd_cache *fdc,
216 struct bt_fd_cache_handle *handle)
217 {
218 struct fd_handle_internal *fd_internal;
219
220 if (!handle) {
221 goto end;
222 }
223
224 fd_internal = (struct fd_handle_internal *) handle;
225
226 BT_ASSERT(fd_internal->ref_count > 0);
227
228 if (fd_internal->ref_count > 1) {
229 fd_internal->ref_count--;
230 } else {
231 gboolean ret;
232 int close_ret;
233
234 close_ret = close(fd_internal->fd_handle.fd);
235 if (close_ret == -1) {
236 BT_LOGW_ERRNO("Failed to close file descriptor",
237 ": fd=%d", fd_internal->fd_handle.fd);
238 }
239 ret = g_hash_table_remove(fdc->cache, fd_internal->key);
240 BT_ASSERT(ret);
241 }
242
243 end:
244 return;
245 }
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