lib/vfs/gc.c

   1 /*
   2    Virtual File System garbage collection code
   3
   4    Copyright (C) 2003-2018
   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
  49 #include "vfs.h"
  50 #include "utilvfs.h"
  51
  52 #include "gc.h"
  53
  54 /*
  55  * The garbage collection mechanism is based on "stamps".
  56  *
  57  * A stamp is a record that says "I'm a filesystem which is no longer in
  58  * use. Free me when you get a chance."
  59  *
  60  * This file contains a set of functions used for managing this stamp. You
  61  * should use them when you write your own filesystem. Here are some rules
  62  * of thumb:
  63  *
  64  * (1) When the last open file in your filesystem gets closed, conditionally
  65  *     create a stamp. You do this with vfs_stamp_create(). (The meaning
  66  *     of "conditionaly" is explained below.)
  67  *
  68  * (2) When a file in your filesystem is opened, delete the stamp. You do
  69  *     this with vfs_rmstamp().
  70  *
  71  * (3) When a path inside your filesystem is invoked, call vfs_stamp() to
  72  *     postpone the free'ing of your filesystem a bit. (This simply updates
  73  *     a timestamp variable inside the stamp.)
  74  *
  75  * Additionally, when a user navigates to a new directory in a panel (or a
  76  * programmer uses mc_chdir()), a stamp is conditionally created for the
  77  * previous directory's filesystem. This ensures that that filesystem is
  78  * free'ed. (see: _do_panel_cd() -> vfs_release_path(); mc_chdir()).
  79  *
  80  * We've spoken here of "conditionally creating" a stamp. What we mean is
  81  * that vfs_stamp_create() is to be used: this function creates a stamp
  82  * only if no directories are open (aka "active") in your filesystem. (If
  83  * there _are_ directories open, it means that the filesystem is in use, in
  84  * which case we don't want to free it.)
  85  */
  86
  87 /*** global variables ****************************************************************************/
  88
  89 int vfs_timeout = 60;           /* VFS timeout in seconds */
  90
  91 /*** file scope macro definitions ****************************************************************/
  92
  93 /*** file scope type declarations ****************************************************************/
  94
  95 /*** file scope variables ************************************************************************/
  96
  97 static struct vfs_stamping *stamps;
  98
  99 /*** file scope functions ************************************************************************/
 100 /* --------------------------------------------------------------------------------------------- */
 101
 102 static void
 103 vfs_addstamp (struct vfs_class *v, vfsid id)
 104 {
 105     if (!(v->flags & VFSF_LOCAL) && id != NULL)
 106     {
 107         struct vfs_stamping *stamp;
 108         struct vfs_stamping *last_stamp = NULL;
 109
 110         for (stamp = stamps; stamp != NULL; stamp = stamp->next)
 111         {
 112             if (stamp->v == v && stamp->id == id)
 113             {
 114                 gettimeofday (&(stamp->time), NULL);
 115                 return;
 116             }
 117             last_stamp = stamp;
 118         }
 119         stamp = g_new (struct vfs_stamping, 1);
 120         stamp->v = v;
 121         stamp->id = id;
 122
 123         gettimeofday (&(stamp->time), NULL);
 124         stamp->next = 0;
 125
 126         if (stamps)
 127         {
 128             /* Add to the end */
 129             last_stamp->next = stamp;
 130         }
 131         else
 132         {
 133             /* Add first element */
 134             stamps = stamp;
 135         }
 136     }
 137 }
 138
 139 /* --------------------------------------------------------------------------------------------- */
 140 /** Compare two timeval structures.  Return 0 is t1 is less than t2. */
 141
 142 static inline int
 143 timeoutcmp (struct timeval *t1, struct timeval *t2)
 144 {
 145     return ((t1->tv_sec < t2->tv_sec)
 146             || ((t1->tv_sec == t2->tv_sec) && (t1->tv_usec <= t2->tv_usec)));
 147 }
 148
 149 /* --------------------------------------------------------------------------------------------- */
 150 /*** public functions ****************************************************************************/
 151 /* --------------------------------------------------------------------------------------------- */
 152
 153 void
 154 vfs_stamp (struct vfs_class *v, vfsid id)
 155 {
 156     struct vfs_stamping *stamp;
 157
 158     for (stamp = stamps; stamp != NULL; stamp = stamp->next)
 159         if (stamp->v == v && stamp->id == id)
 160         {
 161             gettimeofday (&(stamp->time), NULL);
 162             return;
 163         }
 164 }
 165
 166 /* --------------------------------------------------------------------------------------------- */
 167
 168 void
 169 vfs_rmstamp (struct vfs_class *v, vfsid id)
 170 {
 171     struct vfs_stamping *stamp, *st1;
 172
 173     for (stamp = stamps, st1 = NULL; stamp != NULL; st1 = stamp, stamp = stamp->next)
 174         if (stamp->v == v && stamp->id == id)
 175         {
 176             if (st1 == NULL)
 177             {
 178                 stamps = stamp->next;
 179             }
 180             else
 181             {
 182                 st1->next = stamp->next;
 183             }
 184             g_free (stamp);
 185
 186             return;
 187         }
 188 }
 189
 190 /* --------------------------------------------------------------------------------------------- */
 191
 192 void
 193 vfs_stamp_path (const vfs_path_t * vpath)
 194 {
 195     vfsid id;
 196     const vfs_path_element_t *path_element;
 197
 198     path_element = vfs_path_get_by_index (vpath, -1);
 199
 200     id = vfs_getid (vpath);
 201     vfs_addstamp (path_element->class, id);
 202 }
 203
 204 /* --------------------------------------------------------------------------------------------- */
 205 /**
 206  * Create a new timestamp item by VFS class and VFS id.
 207  */
 208
 209 void
 210 vfs_stamp_create (struct vfs_class *vclass, vfsid id)
 211 {
 212     vfsid nvfsid;
 213
 214     ev_vfs_stamp_create_t event_data = { vclass, id, FALSE };
 215     const vfs_path_t *vpath;
 216     const vfs_path_element_t *path_element;
 217
 218     /* There are three directories we have to take care of: current_dir,
 219        current_panel->cwd and other_panel->cwd. Athough most of the time either
 220        current_dir and current_panel->cwd or current_dir and other_panel->cwd are the
 221        same, it's possible that all three are different -- Norbert */
 222
 223     if (!mc_event_present (MCEVENT_GROUP_CORE, "vfs_timestamp"))
 224         return;
 225
 226     vpath = vfs_get_raw_current_dir ();
 227     path_element = vfs_path_get_by_index (vpath, -1);
 228
 229     nvfsid = vfs_getid (vpath);
 230     vfs_rmstamp (path_element->class, nvfsid);
 231
 232     if (!(id == NULL || (path_element->class == vclass && nvfsid == id)))
 233     {
 234         mc_event_raise (MCEVENT_GROUP_CORE, "vfs_timestamp", (gpointer) & event_data);
 235
 236         if (!event_data.ret && vclass != NULL && vclass->nothingisopen != NULL
 237             && vclass->nothingisopen (id) != 0)
 238             vfs_addstamp (vclass, id);
 239     }
 240 }
 241
 242 /* --------------------------------------------------------------------------------------------- */
 243 /** This is called from timeout handler with now = 0, or can be called
 244    with now = 1 to force freeing all filesystems that are not in use */
 245
 246 void
 247 vfs_expire (gboolean now)
 248 {
 249     static gboolean locked = FALSE;
 250     struct timeval lc_time;
 251     struct vfs_stamping *stamp, *st;
 252
 253     /* Avoid recursive invocation, e.g. when one of the free functions
 254        calls message */
 255     if (locked)
 256         return;
 257     locked = TRUE;
 258
 259     gettimeofday (&lc_time, NULL);
 260     lc_time.tv_sec -= vfs_timeout;
 261
 262     for (stamp = stamps; stamp != NULL;)
 263     {
 264         if (now || (timeoutcmp (&stamp->time, &lc_time)))
 265         {
 266             st = stamp->next;
 267             if (stamp->v->free)
 268                 (*stamp->v->free) (stamp->id);
 269             vfs_rmstamp (stamp->v, stamp->id);
 270             stamp = st;
 271         }
 272         else
 273             stamp = stamp->next;
 274     }
 275
 276     locked = FALSE;
 277 }
 278
 279 /* --------------------------------------------------------------------------------------------- */
 280 /*
 281  * Return the number of seconds remaining to the vfs timeout.
 282  * FIXME: The code should be improved to actually return the number of
 283  * seconds until the next item times out.
 284  */
 285
 286 int
 287 vfs_timeouts (void)
 288 {
 289     return stamps ? 10 : 0;
 290 }
 291
 292 /* --------------------------------------------------------------------------------------------- */
 293
 294 void
 295 vfs_timeout_handler (void)
 296 {
 297     vfs_expire (FALSE);
 298 }
 299
 300 /* --------------------------------------------------------------------------------------------- */
 301
 302 void
 303 vfs_release_path (const vfs_path_t * vpath)
 304 {
 305     const vfs_path_element_t *path_element;
 306
 307     path_element = vfs_path_get_by_index (vpath, -1);
 308     vfs_stamp_create (path_element->class, vfs_getid (vpath));
 309 }
 310
 311 /* --------------------------------------------------------------------------------------------- */
 312 /* Free all data */
 313
 314 void
 315 vfs_gc_done (void)
 316 {
 317     struct vfs_stamping *stamp, *st;
 318
 319     for (stamp = stamps, stamps = 0; stamp != NULL;)
 320     {
 321         if (stamp->v->free)
 322             (*stamp->v->free) (stamp->id);
 323         st = stamp->next;
 324         g_free (stamp);
 325         stamp = st;
 326     }
 327
 328     if (stamps)
 329         vfs_rmstamp (stamps->v, stamps->id);
 330 }
 331
 332 /* --------------------------------------------------------------------------------------------- */