util/filemonitor-inotify.c

   1 /*
   2  * QEMU file monitor Linux inotify impl
   3  *
   4  * Copyright (c) 2018 Red Hat, Inc.
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  18  *
  19  */
  20
  21 #include "qemu/osdep.h"
  22 #include "qemu/filemonitor.h"
  23 #include "qemu/main-loop.h"
  24 #include "qemu/error-report.h"
  25 #include "qapi/error.h"
  26 #include "trace.h"
  27
  28 #include <sys/inotify.h>
  29
  30 struct QFileMonitor {
  31     int fd;
  32     QemuMutex lock; /* protects dirs & idmap */
  33     GHashTable *dirs; /* dirname => QFileMonitorDir */
  34     GHashTable *idmap; /* inotify ID => dirname */
  35 };
  36
  37
  38 typedef struct {
  39     int64_t id; /* watch ID */
  40     char *filename; /* optional filter */
  41     QFileMonitorHandler cb;
  42     void *opaque;
  43 } QFileMonitorWatch;
  44
  45
  46 typedef struct {
  47     char *path;
  48     int inotify_id; /* inotify ID */
  49     int next_file_id; /* file ID counter */
  50     GArray *watches; /* QFileMonitorWatch elements */
  51 } QFileMonitorDir;
  52
  53
  54 static void qemu_file_monitor_watch(void *arg)
  55 {
  56     QFileMonitor *mon = arg;
  57     char buf[4096]
  58         __attribute__ ((aligned(__alignof__(struct inotify_event))));
  59     int used = 0;
  60     int len;
  61
  62     qemu_mutex_lock(&mon->lock);
  63
  64     if (mon->fd == -1) {
  65         qemu_mutex_unlock(&mon->lock);
  66         return;
  67     }
  68
  69     len = read(mon->fd, buf, sizeof(buf));
  70
  71     if (len < 0) {
  72         if (errno != EAGAIN) {
  73             error_report("Failure monitoring inotify FD '%s',"
  74                          "disabling events", strerror(errno));
  75             goto cleanup;
  76         }
  77
  78         /* no more events right now */
  79         goto cleanup;
  80     }
  81
  82     /* Loop over all events in the buffer */
  83     while (used < len) {
  84         const char *name;
  85         QFileMonitorDir *dir;
  86         uint32_t iev;
  87         int qev;
  88         gsize i;
  89         struct inotify_event *ev = (struct inotify_event *)(buf + used);
  90
  91         /*
  92          * We trust the kenel to provide valid buffer with complete event
  93          * records.
  94          */
  95         assert(len - used >= sizeof(struct inotify_event));
  96         assert(len - used - sizeof(struct inotify_event) >= ev->len);
  97
  98         name = ev->len ? ev->name : "";
  99         dir = g_hash_table_lookup(mon->idmap, GINT_TO_POINTER(ev->wd));
 100         iev = ev->mask &
 101             (IN_CREATE | IN_MODIFY | IN_DELETE | IN_IGNORED |
 102              IN_MOVED_TO | IN_MOVED_FROM | IN_ATTRIB);
 103
 104         used += sizeof(struct inotify_event) + ev->len;
 105
 106         if (!dir) {
 107             continue;
 108         }
 109
 110         /*
 111          * During a rename operation, the old name gets
 112          * IN_MOVED_FROM and the new name gets IN_MOVED_TO.
 113          * To simplify life for callers, we turn these into
 114          * DELETED and CREATED events
 115          */
 116         switch (iev) {
 117         case IN_CREATE:
 118         case IN_MOVED_TO:
 119             qev = QFILE_MONITOR_EVENT_CREATED;
 120             break;
 121         case IN_MODIFY:
 122             qev = QFILE_MONITOR_EVENT_MODIFIED;
 123             break;
 124         case IN_DELETE:
 125         case IN_MOVED_FROM:
 126             qev = QFILE_MONITOR_EVENT_DELETED;
 127             break;
 128         case IN_ATTRIB:
 129             qev = QFILE_MONITOR_EVENT_ATTRIBUTES;
 130             break;
 131         case IN_IGNORED:
 132             qev = QFILE_MONITOR_EVENT_IGNORED;
 133             break;
 134         default:
 135             g_assert_not_reached();
 136         }
 137
 138         trace_qemu_file_monitor_event(mon, dir->path, name, ev->mask,
 139                                       dir->inotify_id);
 140         for (i = 0; i < dir->watches->len; i++) {
 141             QFileMonitorWatch *watch = &g_array_index(dir->watches,
 142                                                       QFileMonitorWatch,
 143                                                       i);
 144
 145             if (watch->filename == NULL ||
 146                 (name && g_str_equal(watch->filename, name))) {
 147                 trace_qemu_file_monitor_dispatch(mon, dir->path, name,
 148                                                  qev, watch->cb,
 149                                                  watch->opaque, watch->id);
 150                 watch->cb(watch->id, qev, name, watch->opaque);
 151             }
 152         }
 153     }
 154
 155  cleanup:
 156     qemu_mutex_unlock(&mon->lock);
 157 }
 158
 159
 160 static void
 161 qemu_file_monitor_dir_free(void *data)
 162 {
 163     QFileMonitorDir *dir = data;
 164     gsize i;
 165
 166     for (i = 0; i < dir->watches->len; i++) {
 167         QFileMonitorWatch *watch = &g_array_index(dir->watches,
 168                                                   QFileMonitorWatch, i);
 169         g_free(watch->filename);
 170     }
 171     g_array_unref(dir->watches);
 172     g_free(dir->path);
 173     g_free(dir);
 174 }
 175
 176
 177 QFileMonitor *
 178 qemu_file_monitor_new(Error **errp)
 179 {
 180     int fd;
 181     QFileMonitor *mon;
 182
 183     fd = inotify_init1(IN_NONBLOCK);
 184     if (fd < 0) {
 185         error_setg_errno(errp, errno,
 186                          "Unable to initialize inotify");
 187         return NULL;
 188     }
 189
 190     mon = g_new0(QFileMonitor, 1);
 191     qemu_mutex_init(&mon->lock);
 192     mon->fd = fd;
 193
 194     mon->dirs = g_hash_table_new_full(g_str_hash, g_str_equal, NULL,
 195                                       qemu_file_monitor_dir_free);
 196     mon->idmap = g_hash_table_new(g_direct_hash, g_direct_equal);
 197
 198     trace_qemu_file_monitor_new(mon, mon->fd);
 199
 200     return mon;
 201 }
 202
 203 static gboolean
 204 qemu_file_monitor_free_idle(void *opaque)
 205 {
 206     QFileMonitor *mon = opaque;
 207
 208     if (!mon) {
 209         return G_SOURCE_REMOVE;
 210     }
 211
 212     qemu_mutex_lock(&mon->lock);
 213
 214     g_hash_table_unref(mon->idmap);
 215     g_hash_table_unref(mon->dirs);
 216
 217     qemu_mutex_unlock(&mon->lock);
 218
 219     qemu_mutex_destroy(&mon->lock);
 220     g_free(mon);
 221
 222     return G_SOURCE_REMOVE;
 223 }
 224
 225 void
 226 qemu_file_monitor_free(QFileMonitor *mon)
 227 {
 228     if (!mon) {
 229         return;
 230     }
 231
 232     qemu_mutex_lock(&mon->lock);
 233     if (mon->fd != -1) {
 234         qemu_set_fd_handler(mon->fd, NULL, NULL, NULL);
 235         close(mon->fd);
 236         mon->fd = -1;
 237     }
 238     qemu_mutex_unlock(&mon->lock);
 239
 240     /*
 241      * Can't free it yet, because another thread
 242      * may be running event loop, so the inotify
 243      * callback might be pending. Using an idle
 244      * source ensures we'll only free after the
 245      * pending callback is done
 246      */
 247     g_idle_add((GSourceFunc)qemu_file_monitor_free_idle, mon);
 248 }
 249
 250 int64_t
 251 qemu_file_monitor_add_watch(QFileMonitor *mon,
 252                             const char *dirpath,
 253                             const char *filename,
 254                             QFileMonitorHandler cb,
 255                             void *opaque,
 256                             Error **errp)
 257 {
 258     QFileMonitorDir *dir;
 259     QFileMonitorWatch watch;
 260     int64_t ret = -1;
 261
 262     qemu_mutex_lock(&mon->lock);
 263     dir = g_hash_table_lookup(mon->dirs, dirpath);
 264     if (!dir) {
 265         int rv = inotify_add_watch(mon->fd, dirpath,
 266                                    IN_CREATE | IN_DELETE | IN_MODIFY |
 267                                    IN_MOVED_TO | IN_MOVED_FROM | IN_ATTRIB);
 268
 269         if (rv < 0) {
 270             error_setg_errno(errp, errno, "Unable to watch '%s'", dirpath);
 271             goto cleanup;
 272         }
 273
 274         trace_qemu_file_monitor_enable_watch(mon, dirpath, rv);
 275
 276         dir = g_new0(QFileMonitorDir, 1);
 277         dir->path = g_strdup(dirpath);
 278         dir->inotify_id = rv;
 279         dir->watches = g_array_new(FALSE, TRUE, sizeof(QFileMonitorWatch));
 280
 281         g_hash_table_insert(mon->dirs, dir->path, dir);
 282         g_hash_table_insert(mon->idmap, GINT_TO_POINTER(rv), dir);
 283
 284         if (g_hash_table_size(mon->dirs) == 1) {
 285             qemu_set_fd_handler(mon->fd, qemu_file_monitor_watch, NULL, mon);
 286         }
 287     }
 288
 289     watch.id = (((int64_t)dir->inotify_id) << 32) | dir->next_file_id++;
 290     watch.filename = g_strdup(filename);
 291     watch.cb = cb;
 292     watch.opaque = opaque;
 293
 294     g_array_append_val(dir->watches, watch);
 295
 296     trace_qemu_file_monitor_add_watch(mon, dirpath,
 297                                       filename ? filename : "<none>",
 298                                       cb, opaque, watch.id);
 299
 300     ret = watch.id;
 301
 302  cleanup:
 303     qemu_mutex_unlock(&mon->lock);
 304     return ret;
 305 }
 306
 307
 308 void qemu_file_monitor_remove_watch(QFileMonitor *mon,
 309                                     const char *dirpath,
 310                                     int64_t id)
 311 {
 312     QFileMonitorDir *dir;
 313     gsize i;
 314
 315     qemu_mutex_lock(&mon->lock);
 316
 317     trace_qemu_file_monitor_remove_watch(mon, dirpath, id);
 318
 319     dir = g_hash_table_lookup(mon->dirs, dirpath);
 320     if (!dir) {
 321         goto cleanup;
 322     }
 323
 324     for (i = 0; i < dir->watches->len; i++) {
 325         QFileMonitorWatch *watch = &g_array_index(dir->watches,
 326                                                   QFileMonitorWatch, i);
 327         if (watch->id == id) {
 328             g_free(watch->filename);
 329             g_array_remove_index(dir->watches, i);
 330             break;
 331         }
 332     }
 333
 334     if (dir->watches->len == 0) {
 335         inotify_rm_watch(mon->fd, dir->inotify_id);
 336         trace_qemu_file_monitor_disable_watch(mon, dir->path, dir->inotify_id);
 337
 338         g_hash_table_remove(mon->idmap, GINT_TO_POINTER(dir->inotify_id));
 339         g_hash_table_remove(mon->dirs, dir->path);
 340
 341         if (g_hash_table_size(mon->dirs) == 0) {
 342             qemu_set_fd_handler(mon->fd, NULL, NULL, NULL);
 343         }
 344     }
 345
 346  cleanup:
 347     qemu_mutex_unlock(&mon->lock);
 348 }