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1e638f98 FD |
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 <babeltrace/assert-internal.h> | |
39 | #include <babeltrace/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; | |
139 | ||
140 | ret = stat(path, &statbuf); | |
141 | if (ret < 0) { | |
142 | BT_LOGE_ERRNO("Failed to stat file", ": path=%s", path); | |
143 | goto end; | |
144 | } | |
145 | ||
146 | /* | |
147 | * Use the device number and inode number to uniquely identify a file. | |
148 | * Even if the file as the same path, it may have been replaced so we | |
149 | * must open a new FD for it. This replacement of file is more likely | |
150 | * to happen with a lttng-live source component. | |
151 | */ | |
152 | fk.dev = statbuf.st_dev; | |
153 | fk.ino = statbuf.st_ino; | |
154 | ||
155 | fd_internal = g_hash_table_lookup(fdc->cache, &fk); | |
156 | if (!fd_internal) { | |
157 | gboolean ret; | |
158 | struct file_key *file_key; | |
159 | ||
160 | int fd = open(path, O_RDONLY); | |
161 | if (fd < 0) { | |
162 | BT_LOGE_ERRNO("Failed to open file", "path=%s", path); | |
163 | goto error; | |
164 | } | |
165 | ||
166 | fd_internal = g_new0(struct fd_handle_internal, 1); | |
167 | if (!fd_internal) { | |
168 | BT_LOGE("Failed to allocate fd internal handle"); | |
169 | goto error; | |
170 | } | |
171 | ||
172 | file_key = g_new0(struct file_key, 1); | |
173 | if (!fd_internal) { | |
174 | BT_LOGE("Failed to allocate file key"); | |
175 | goto error; | |
176 | } | |
177 | ||
178 | *file_key = fk; | |
179 | ||
180 | fd_internal->fd_handle.fd = fd; | |
181 | fd_internal->ref_count = 0; | |
182 | fd_internal->key = file_key; | |
183 | ||
184 | /* Insert the newly created fd handle. */ | |
185 | ret = g_hash_table_insert(fdc->cache, fd_internal->key, | |
186 | fd_internal); | |
187 | BT_ASSERT(ret); | |
188 | } | |
189 | ||
190 | BT_ASSERT(fd_internal->ref_count >= 0); | |
191 | ||
192 | fd_internal->ref_count++; | |
193 | goto end; | |
194 | ||
195 | error: | |
196 | fd_cache_handle_internal_destroy(fd_internal); | |
197 | fd_internal = NULL; | |
198 | end: | |
199 | return (struct bt_fd_cache_handle *) fd_internal; | |
200 | } | |
201 | ||
202 | BT_HIDDEN | |
203 | void bt_fd_cache_put_handle(struct bt_fd_cache *fdc, | |
204 | struct bt_fd_cache_handle *handle) | |
205 | { | |
206 | struct fd_handle_internal *fd_internal; | |
207 | ||
208 | if (!handle) { | |
209 | goto end; | |
210 | } | |
211 | ||
212 | fd_internal = (struct fd_handle_internal *) handle; | |
213 | ||
214 | BT_ASSERT(fd_internal->ref_count > 0); | |
215 | ||
216 | if (fd_internal->ref_count > 1) { | |
217 | fd_internal->ref_count--; | |
218 | } else { | |
219 | gboolean ret; | |
220 | int close_ret; | |
221 | ||
222 | close_ret = close(fd_internal->fd_handle.fd); | |
223 | if (close_ret == -1) { | |
224 | BT_LOGW_ERRNO("Failed to close file descriptor", | |
225 | ": fd=%d", fd_internal->fd_handle.fd); | |
226 | } | |
227 | ret = g_hash_table_remove(fdc->cache, fd_internal->key); | |
228 | BT_ASSERT(ret); | |
229 | } | |
230 | ||
231 | end: | |
232 | return; | |
233 | } |