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1 /*
2 Virtual File System garbage collection code
3
4 Copyright (C) 2003-2019
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> /* For atol() */
43 #include <sys/types.h>
44 #include <sys/time.h> /* gettimeofday() */
45
46 #include "lib/global.h"
47 #include "lib/event.h"
48 #include "lib/util.h" /* MC_PTR_FREE */
49
50 #include "vfs.h"
51 #include "utilvfs.h"
52
53 #include "gc.h"
54
55 /*
56 * The garbage collection mechanism is based on "stamps".
57 *
58 * A stamp is a record that says "I'm a filesystem which is no longer in
59 * use. Free me when you get a chance."
60 *
61 * This file contains a set of functions used for managing this stamp. You
62 * should use them when you write your own filesystem. Here are some rules
63 * of thumb:
64 *
65 * (1) When the last open file in your filesystem gets closed, conditionally
66 * create a stamp. You do this with vfs_stamp_create(). (The meaning
67 * of "conditionaly" is explained below.)
68 *
69 * (2) When a file in your filesystem is opened, delete the stamp. You do
70 * this with vfs_rmstamp().
71 *
72 * (3) When a path inside your filesystem is invoked, call vfs_stamp() to
73 * postpone the free'ing of your filesystem a bit. (This simply updates
74 * a timestamp variable inside the stamp.)
75 *
76 * Additionally, when a user navigates to a new directory in a panel (or a
77 * programmer uses mc_chdir()), a stamp is conditionally created for the
78 * previous directory's filesystem. This ensures that that filesystem is
79 * free'ed. (see: _do_panel_cd() -> vfs_release_path(); mc_chdir()).
80 *
81 * We've spoken here of "conditionally creating" a stamp. What we mean is
82 * that vfs_stamp_create() is to be used: this function creates a stamp
83 * only if no directories are open (aka "active") in your filesystem. (If
84 * there _are_ directories open, it means that the filesystem is in use, in
85 * which case we don't want to free it.)
86 */
87
88 /*** global variables ****************************************************************************/
89
90 int vfs_timeout = 60; /* VFS timeout in seconds */
91
92 /*** file scope macro definitions ****************************************************************/
93
94 #define VFS_STAMPING(a) ((struct vfs_stamping *)(a))
95
96 /*** file scope type declarations ****************************************************************/
97
98 struct vfs_stamping
99 {
100 struct vfs_class *v;
101 vfsid id;
102 struct timeval time;
103 };
104
105 /*** file scope variables ************************************************************************/
106
107 static GSList *stamps = NULL;
108
109 /* --------------------------------------------------------------------------------------------- */
110 /*** file scope functions ************************************************************************/
111 /* --------------------------------------------------------------------------------------------- */
112
113 /** Compare two timeval structures. Return TRUE if t1 is less than t2. */
114
115 static gboolean
116 timeoutcmp (const struct timeval *t1, const struct timeval *t2)
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*/
117 {
118 return ((t1->tv_sec < t2->tv_sec)
119 || ((t1->tv_sec == t2->tv_sec) && (t1->tv_usec <= t2->tv_usec)));
120 }
121
122 /* --------------------------------------------------------------------------------------------- */
123
124 static gint
125 vfs_stamp_compare (gconstpointer a, gconstpointer b)
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*/
126 {
127 const struct vfs_stamping *vsa = (const struct vfs_stamping *) a;
128 const struct vfs_stamping *vsb = (const struct vfs_stamping *) b;
129
130 return (vsa == NULL || vsb == NULL || (vsa->v == vsb->v && vsa->id == vsb->id)) ? 0 : 1;
131 }
132
133 /* --------------------------------------------------------------------------------------------- */
134
135 static void
136 vfs_addstamp (struct vfs_class *v, vfsid id)
/* */
137 {
138 if ((v->flags & VFS_LOCAL) == 0 && id != NULL && !vfs_stamp (v, id))
139 {
140 struct vfs_stamping *stamp;
141
142 stamp = g_new (struct vfs_stamping, 1);
143 stamp->v = v;
144 stamp->id = id;
145 gettimeofday (&(stamp->time), NULL);
146
147 stamps = g_slist_append (stamps, stamp);
148 }
149 }
150
151 /* --------------------------------------------------------------------------------------------- */
152 /*** public functions ****************************************************************************/
153 /* --------------------------------------------------------------------------------------------- */
154
155 gboolean
156 vfs_stamp (struct vfs_class *v, vfsid id)
/* */
157 {
158 struct vfs_stamping what = {
159 .v = v,
160 .id = id
161 };
162 GSList *stamp;
163 gboolean ret = FALSE;
164
165 stamp = g_slist_find_custom (stamps, &what, vfs_stamp_compare);
166 if (stamp != NULL && stamp->data != NULL)
167 {
168 gettimeofday (&(VFS_STAMPING (stamp->data)->time), NULL);
169 ret = TRUE;
170 }
171
172 return ret;
173 }
174
175 /* --------------------------------------------------------------------------------------------- */
176
177 void
178 vfs_rmstamp (struct vfs_class *v, vfsid id)
/* */
179 {
180 struct vfs_stamping what = {
181 .v = v,
182 .id = id
183 };
184 GSList *stamp;
185
186 stamp = g_slist_find_custom (stamps, &what, vfs_stamp_compare);
187 if (stamp != NULL)
188 {
189 g_free (stamp->data);
190 stamps = g_slist_delete_link (stamps, stamp);
191 }
192 }
193
194 /* --------------------------------------------------------------------------------------------- */
195
196 void
197 vfs_stamp_path (const vfs_path_t * vpath)
/* */
198 {
199 vfsid id;
200 const vfs_path_element_t *path_element;
201
202 path_element = vfs_path_get_by_index (vpath, -1);
203
204 id = vfs_getid (vpath);
205 vfs_addstamp (path_element->class, id);
206 }
207
208 /* --------------------------------------------------------------------------------------------- */
209 /**
210 * Create a new timestamp item by VFS class and VFS id.
211 */
212
213 void
214 vfs_stamp_create (struct vfs_class *vclass, vfsid id)
/* */
215 {
216 vfsid nvfsid;
217
218 ev_vfs_stamp_create_t event_data = { vclass, id, FALSE };
219 const vfs_path_t *vpath;
220 const vfs_path_element_t *path_element;
221
222 /* There are three directories we have to take care of: current_dir,
223 current_panel->cwd and other_panel->cwd. Athough most of the time either
224 current_dir and current_panel->cwd or current_dir and other_panel->cwd are the
225 same, it's possible that all three are different -- Norbert */
226
227 if (!mc_event_present (MCEVENT_GROUP_CORE, "vfs_timestamp"))
228 return;
229
230 vpath = vfs_get_raw_current_dir ();
231 path_element = vfs_path_get_by_index (vpath, -1);
232
233 nvfsid = vfs_getid (vpath);
234 vfs_rmstamp (path_element->class, nvfsid);
235
236 if (!(id == NULL || (path_element->class == vclass && nvfsid == id)))
237 {
238 mc_event_raise (MCEVENT_GROUP_CORE, "vfs_timestamp", (gpointer) & event_data);
239
240 if (!event_data.ret && vclass != NULL && vclass->nothingisopen != NULL
241 && vclass->nothingisopen (id))
242 vfs_addstamp (vclass, id);
243 }
244 }
245
246 /* --------------------------------------------------------------------------------------------- */
247 /** This is called from timeout handler with now = FALSE,
248 or can be called with now = TRUE to force freeing all filesystems */
249
250 void
251 vfs_expire (gboolean now)
/* */
252 {
253 static gboolean locked = FALSE;
254 struct timeval curr_time, exp_time;
255 GSList *stamp;
256
257 /* Avoid recursive invocation, e.g. when one of the free functions
258 calls message */
259 if (locked)
260 return;
261 locked = TRUE;
262
263 gettimeofday (&curr_time, NULL);
264 exp_time.tv_sec = curr_time.tv_sec - vfs_timeout;
265 exp_time.tv_usec = curr_time.tv_usec;
266
267 if (now)
268 {
269 /* reverse list to free nested VFSes at first */
270 stamps = g_slist_reverse (stamps);
271 }
272
273 /* NULLize stamps that point to expired VFS */
274 for (stamp = stamps; stamp != NULL; stamp = g_slist_next (stamp))
275 {
276 struct vfs_stamping *stamping = VFS_STAMPING (stamp->data);
277
278 if (now)
279 {
280 /* free VFS forced */
281 if (stamping->v->free != NULL)
282 stamping->v->free (stamping->id);
283 MC_PTR_FREE (stamp->data);
284 }
285 else if (timeoutcmp (&stamping->time, &exp_time))
286 {
287 /* update timestamp of VFS that is in use, or free unused VFS */
288 if (stamping->v->nothingisopen != NULL && !stamping->v->nothingisopen (stamping->id))
289 stamping->time = curr_time;
290 else
291 {
292 if (stamping->v->free != NULL)
293 stamping->v->free (stamping->id);
294 MC_PTR_FREE (stamp->data);
295 }
296 }
297 }
298
299 /* then remove NULLized stamps */
300 stamps = g_slist_remove_all (stamps, NULL);
301
302 locked = FALSE;
303 }
304
305 /* --------------------------------------------------------------------------------------------- */
306 /*
307 * Return the number of seconds remaining to the vfs timeout.
308 * FIXME: The code should be improved to actually return the number of
309 * seconds until the next item times out.
310 */
311
312 int
313 vfs_timeouts (void)
/* */
314 {
315 return stamps != NULL ? 10 : 0;
316 }
317
318 /* --------------------------------------------------------------------------------------------- */
319
320 void
321 vfs_timeout_handler (void)
/* */
322 {
323 vfs_expire (FALSE);
324 }
325
326 /* --------------------------------------------------------------------------------------------- */
327
328 void
329 vfs_release_path (const vfs_path_t * vpath)
/* */
330 {
331 const vfs_path_element_t *path_element;
332
333 path_element = vfs_path_get_by_index (vpath, -1);
334 vfs_stamp_create (path_element->class, vfs_getid (vpath));
335 }
336
337 /* --------------------------------------------------------------------------------------------- */
338 /* Free all data */
339
340 void
341 vfs_gc_done (void)
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*/
342 {
343 vfs_expire (TRUE);
344 }
345
346 /* --------------------------------------------------------------------------------------------- */
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*/