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*/
1 /*
2 Virtual File System garbage collection code
3
4 Copyright (C) 2003-2022
5 Free Software Foundation, Inc.
6
7 Written by:
8 Miguel de Icaza, 1995
9 Jakub Jelinek, 1995
10 Pavel Machek, 1998
11 Pavel Roskin, 2003
12
13 This file is part of the Midnight Commander.
14
15 The Midnight Commander is free software: you can redistribute it
16 and/or modify it under the terms of the GNU General Public License as
17 published by the Free Software Foundation, either version 3 of the License,
18 or (at your option) any later version.
19
20 The Midnight Commander is distributed in the hope that it will be useful,
21 but WITHOUT ANY WARRANTY; without even the implied warranty of
22 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 GNU General Public License for more details.
24
25 You should have received a copy of the GNU General Public License
26 along with this program. If not, see <http://www.gnu.org/licenses/>.
27 */
28
29 /**
30 * \file
31 * \brief Source: Virtual File System: garbage collection code
32 * \author Miguel de Icaza
33 * \author Jakub Jelinek
34 * \author Pavel Machek
35 * \author Pavel Roskin
36 * \date 1995, 1998, 2003
37 */
38
39
40 #include <config.h>
41
42 #include <stdlib.h>
43
44 #include "lib/global.h"
45 #include "lib/event.h"
46 #include "lib/util.h" /* MC_PTR_FREE */
47
48 #include "vfs.h"
49 #include "utilvfs.h"
50
51 #include "gc.h"
52
53 /*
54 * The garbage collection mechanism is based on "stamps".
55 *
56 * A stamp is a record that says "I'm a filesystem which is no longer in
57 * use. Free me when you get a chance."
58 *
59 * This file contains a set of functions used for managing this stamp. You
60 * should use them when you write your own filesystem. Here are some rules
61 * of thumb:
62 *
63 * (1) When the last open file in your filesystem gets closed, conditionally
64 * create a stamp. You do this with vfs_stamp_create(). (The meaning
65 * of "conditionaly" is explained below.)
66 *
67 * (2) When a file in your filesystem is opened, delete the stamp. You do
68 * this with vfs_rmstamp().
69 *
70 * (3) When a path inside your filesystem is invoked, call vfs_stamp() to
71 * postpone the free'ing of your filesystem a bit. (This simply updates
72 * a timestamp variable inside the stamp.)
73 *
74 * Additionally, when a user navigates to a new directory in a panel (or a
75 * programmer uses mc_chdir()), a stamp is conditionally created for the
76 * previous directory's filesystem. This ensures that that filesystem is
77 * free'ed. (see: _do_panel_cd() -> vfs_release_path(); mc_chdir()).
78 *
79 * We've spoken here of "conditionally creating" a stamp. What we mean is
80 * that vfs_stamp_create() is to be used: this function creates a stamp
81 * only if no directories are open (aka "active") in your filesystem. (If
82 * there _are_ directories open, it means that the filesystem is in use, in
83 * which case we don't want to free it.)
84 */
85
86 /*** global variables ****************************************************************************/
87
88 int vfs_timeout = 60; /* VFS timeout in seconds */
89
90 /*** file scope macro definitions ****************************************************************/
91
92 #define VFS_STAMPING(a) ((struct vfs_stamping *)(a))
93
94 /*** file scope type declarations ****************************************************************/
95
96 struct vfs_stamping
97 {
98 struct vfs_class *v;
99 vfsid id;
100 gint64 time;
101 };
102
103 /*** file scope variables ************************************************************************/
104
105 static GSList *stamps = NULL;
106
107 /* --------------------------------------------------------------------------------------------- */
108 /*** file scope functions ************************************************************************/
109 /* --------------------------------------------------------------------------------------------- */
110
111 static gint
112 vfs_stamp_compare (gconstpointer a, gconstpointer b)
/* ![[next]](../icons/right.png)
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*/
113 {
114 const struct vfs_stamping *vsa = (const struct vfs_stamping *) a;
115 const struct vfs_stamping *vsb = (const struct vfs_stamping *) b;
116
117 return (vsa == NULL || vsb == NULL || (vsa->v == vsb->v && vsa->id == vsb->id)) ? 0 : 1;
118 }
119
120 /* --------------------------------------------------------------------------------------------- */
121
122 static void
123 vfs_addstamp (struct vfs_class *v, vfsid id)
/* ![[previous]](../icons/left.png)
*/
124 {
125 if ((v->flags & VFSF_LOCAL) == 0 && id != NULL && !vfs_stamp (v, id))
126 {
127 struct vfs_stamping *stamp;
128
129 stamp = g_new (struct vfs_stamping, 1);
130 stamp->v = v;
131 stamp->id = id;
132 stamp->time = g_get_monotonic_time ();
133
134 stamps = g_slist_append (stamps, stamp);
135 }
136 }
137
138 /* --------------------------------------------------------------------------------------------- */
139 /*** public functions ****************************************************************************/
140 /* --------------------------------------------------------------------------------------------- */
141
142 gboolean
143 vfs_stamp (struct vfs_class *v, vfsid id)
/* */
144 {
145 struct vfs_stamping what = {
146 .v = v,
147 .id = id
148 };
149 GSList *stamp;
150 gboolean ret = FALSE;
151
152 stamp = g_slist_find_custom (stamps, &what, vfs_stamp_compare);
153 if (stamp != NULL && stamp->data != NULL)
154 {
155 VFS_STAMPING (stamp->data)->time = g_get_monotonic_time ();
156 ret = TRUE;
157 }
158
159 return ret;
160 }
161
162 /* --------------------------------------------------------------------------------------------- */
163
164 void
165 vfs_rmstamp (struct vfs_class *v, vfsid id)
/* */
166 {
167 struct vfs_stamping what = {
168 .v = v,
169 .id = id
170 };
171 GSList *stamp;
172
173 stamp = g_slist_find_custom (stamps, &what, vfs_stamp_compare);
174 if (stamp != NULL)
175 {
176 g_free (stamp->data);
177 stamps = g_slist_delete_link (stamps, stamp);
178 }
179 }
180
181 /* --------------------------------------------------------------------------------------------- */
182
183 void
184 vfs_stamp_path (const vfs_path_t * vpath)
/* */
185 {
186 vfsid id;
187 const vfs_path_element_t *path_element;
188
189 path_element = vfs_path_get_by_index (vpath, -1);
190
191 id = vfs_getid (vpath);
192 vfs_addstamp (path_element->class, id);
193 }
194
195 /* --------------------------------------------------------------------------------------------- */
196 /**
197 * Create a new timestamp item by VFS class and VFS id.
198 */
199
200 void
201 vfs_stamp_create (struct vfs_class *vclass, vfsid id)
/* */
202 {
203 vfsid nvfsid;
204
205 ev_vfs_stamp_create_t event_data = { vclass, id, FALSE };
206 const vfs_path_t *vpath;
207 const vfs_path_element_t *path_element;
208
209 /* There are three directories we have to take care of: current_dir,
210 current_panel->cwd and other_panel->cwd. Athough most of the time either
211 current_dir and current_panel->cwd or current_dir and other_panel->cwd are the
212 same, it's possible that all three are different -- Norbert */
213
214 if (!mc_event_present (MCEVENT_GROUP_CORE, "vfs_timestamp"))
215 return;
216
217 vpath = vfs_get_raw_current_dir ();
218 path_element = vfs_path_get_by_index (vpath, -1);
219
220 nvfsid = vfs_getid (vpath);
221 vfs_rmstamp (path_element->class, nvfsid);
222
223 if (!(id == NULL || (path_element->class == vclass && nvfsid == id)))
224 {
225 mc_event_raise (MCEVENT_GROUP_CORE, "vfs_timestamp", (gpointer) & event_data);
226
227 if (!event_data.ret && vclass != NULL && vclass->nothingisopen != NULL
228 && vclass->nothingisopen (id))
229 vfs_addstamp (vclass, id);
230 }
231 }
232
233 /* --------------------------------------------------------------------------------------------- */
234 /** This is called from timeout handler with now = FALSE,
235 or can be called with now = TRUE to force freeing all filesystems */
236
237 void
238 vfs_expire (gboolean now)
/* */
239 {
240 static gboolean locked = FALSE;
241 gint64 curr_time, exp_time;
242 GSList *stamp;
243
244 /* Avoid recursive invocation, e.g. when one of the free functions
245 calls message */
246 if (locked)
247 return;
248 locked = TRUE;
249
250 curr_time = g_get_monotonic_time ();
251 exp_time = curr_time - vfs_timeout * G_USEC_PER_SEC;
252
253 if (now)
254 {
255 /* reverse list to free nested VFSes at first */
256 stamps = g_slist_reverse (stamps);
257 }
258
259 /* NULLize stamps that point to expired VFS */
260 for (stamp = stamps; stamp != NULL; stamp = g_slist_next (stamp))
261 {
262 struct vfs_stamping *stamping = VFS_STAMPING (stamp->data);
263
264 if (now)
265 {
266 /* free VFS forced */
267 if (stamping->v->free != NULL)
268 stamping->v->free (stamping->id);
269 MC_PTR_FREE (stamp->data);
270 }
271 else if (stamping->time <= exp_time)
272 {
273 /* update timestamp of VFS that is in use, or free unused VFS */
274 if (stamping->v->nothingisopen != NULL && !stamping->v->nothingisopen (stamping->id))
275 stamping->time = curr_time;
276 else
277 {
278 if (stamping->v->free != NULL)
279 stamping->v->free (stamping->id);
280 MC_PTR_FREE (stamp->data);
281 }
282 }
283 }
284
285 /* then remove NULLized stamps */
286 stamps = g_slist_remove_all (stamps, NULL);
287
288 locked = FALSE;
289 }
290
291 /* --------------------------------------------------------------------------------------------- */
292 /*
293 * Return the number of seconds remaining to the vfs timeout.
294 * FIXME: The code should be improved to actually return the number of
295 * seconds until the next item times out.
296 */
297
298 int
299 vfs_timeouts (void)
/* */
300 {
301 return stamps != NULL ? 10 : 0;
302 }
303
304 /* --------------------------------------------------------------------------------------------- */
305
306 void
307 vfs_timeout_handler (void)
/* */
308 {
309 vfs_expire (FALSE);
310 }
311
312 /* --------------------------------------------------------------------------------------------- */
313
314 void
315 vfs_release_path (const vfs_path_t * vpath)
/* */
316 {
317 const vfs_path_element_t *path_element;
318
319 path_element = vfs_path_get_by_index (vpath, -1);
320 vfs_stamp_create (path_element->class, vfs_getid (vpath));
321 }
322
323 /* --------------------------------------------------------------------------------------------- */
324 /* Free all data */
325
326 void
327 vfs_gc_done (void)
/* ![[last]](../icons/n_last.png)
*/
328 {
329 vfs_expire (TRUE);
330 }
331
332 /* --------------------------------------------------------------------------------------------- */
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*/