libudev/libudev-queue-private.c

   1 /*
   2  * libudev - interface to udev device information
   3  *
   4  * Copyright (C) 2008 Kay Sievers <kay.sievers@vrfy.org>
   5  * Copyright (C) 2009 Alan Jenkins <alan-jenkins@tuffmail.co.uk>
   6  *
   7  * This library is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  */
  12
  13 /*
  14  * DISCLAIMER - The file format mentioned here is private to udev/libudev,
  15  *              and may be changed without notice.
  16  *
  17  * The udev event queue is exported as a binary log file.
  18  * Each log record consists of a sequence number followed by the device path.
  19  *
  20  * When a new event is queued, its details are appended to the log.
  21  * When the event finishes, a second record is appended to the log
  22  * with the same sequence number but a devpath len of 0.
  23  *
  24  * Example:
  25  *      { 0x0000000000000001 }
  26  *      { 0x0000000000000001, 0x0019, "/devices/virtual/mem/null" },
  27  *      { 0x0000000000000002, 0x001b, "/devices/virtual/mem/random" },
  28  *      { 0x0000000000000001, 0x0000 },
  29  *      { 0x0000000000000003, 0x0019, "/devices/virtual/mem/zero" },
  30  *
  31  * Events 2 and 3 are still queued, but event 1 has finished.
  32  *
  33  * The queue does not grow indefinitely. It is periodically re-created
  34  * to remove finished events. Atomic rename() makes this transparent to readers.
  35  *
  36  * The queue file starts with a single sequence number which specifies the
  37  * minimum sequence number in the log that follows. Any events prior to this
  38  * sequence number have already finished.
  39  */
  40
  41 #include <stdio.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45 #include <fcntl.h>
  46 #include <dirent.h>
  47 #include <limits.h>
  48 #include <errno.h>
  49 #include <sys/stat.h>
  50 #include <sys/types.h>
  51
  52 #include "libudev.h"
  53 #include "libudev-private.h"
  54
  55 static int rebuild_queue_file(struct udev_queue_export *udev_queue_export);
  56
  57 struct udev_queue_export {
  58         struct udev *udev;
  59         int failed_count;       /* number of failed events exported */
  60         int queued_count;       /* number of unfinished events exported in queue file */
  61         FILE *queue_file;
  62         unsigned long long int seqnum_max;      /* earliest sequence number in queue file */
  63         unsigned long long int seqnum_min;      /* latest sequence number in queue file */
  64         int waste_bytes;                        /* queue file bytes wasted on finished events */
  65 };
  66
  67 struct udev_queue_export *udev_queue_export_new(struct udev *udev)
  68 {
  69         struct udev_queue_export *udev_queue_export;
  70         unsigned long long int initial_seqnum;
  71
  72         if (udev == NULL)
  73                 return NULL;
  74
  75         udev_queue_export = calloc(1, sizeof(struct udev_queue_export));
  76         if (udev_queue_export == NULL)
  77                 return NULL;
  78         udev_queue_export->udev = udev;
  79
  80         initial_seqnum = udev_get_kernel_seqnum(udev);
  81         udev_queue_export->seqnum_min = initial_seqnum;
  82         udev_queue_export->seqnum_max = initial_seqnum;
  83
  84         udev_queue_export_cleanup(udev_queue_export);
  85         if (rebuild_queue_file(udev_queue_export) != 0) {
  86                 free(udev_queue_export);
  87                 return NULL;
  88         }
  89
  90         return udev_queue_export;
  91 }
  92
  93 void udev_queue_export_unref(struct udev_queue_export *udev_queue_export)
  94 {
  95         if (udev_queue_export == NULL)
  96                 return;
  97         if (udev_queue_export->queue_file != NULL)
  98                 fclose(udev_queue_export->queue_file);
  99         free(udev_queue_export);
 100 }
 101
 102 void udev_queue_export_cleanup(struct udev_queue_export *udev_queue_export)
 103 {
 104         char filename[UTIL_PATH_SIZE];
 105
 106         util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev_queue_export->udev), "/.udev/queue.tmp", NULL);
 107         unlink(filename);
 108
 109         util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev_queue_export->udev), "/.udev/queue.bin", NULL);
 110         unlink(filename);
 111 }
 112
 113 static int skip_to(FILE *file, long offset)
 114 {
 115         long old_offset;
 116
 117         /* fseek may drop buffered data, avoid it for small seeks */
 118         old_offset = ftell(file);
 119         if (offset > old_offset && offset - old_offset <= BUFSIZ) {
 120                 size_t skip_bytes = offset - old_offset;
 121                 char buf[skip_bytes];
 122
 123                 if (fread(buf, skip_bytes, 1, file) != skip_bytes)
 124                         return -1;
 125         }
 126
 127         return fseek(file, offset, SEEK_SET);
 128 }
 129
 130 struct queue_devpaths {
 131         unsigned int devpaths_first;    /* index of first queued event */
 132         unsigned int devpaths_size;
 133         long devpaths[];                /* seqnum -> offset of devpath in queue file (or 0) */
 134 };
 135
 136 /*
 137  * Returns a table mapping seqnum to devpath file offset for currently queued events.
 138  * devpaths[i] represents the event with seqnum = i + udev_queue_export->seqnum_min.
 139  */
 140 static struct queue_devpaths *build_index(struct udev_queue_export *udev_queue_export)
 141 {
 142         struct queue_devpaths *devpaths;
 143         unsigned long long int range;
 144         long devpath_offset;
 145         ssize_t devpath_len;
 146         unsigned long long int seqnum;
 147         unsigned long long int n;
 148         unsigned int i;
 149
 150         /* seek to the first event in the file */
 151         rewind(udev_queue_export->queue_file);
 152         udev_queue_read_seqnum(udev_queue_export->queue_file, &seqnum);
 153
 154         /* allocate the table */
 155         range = udev_queue_export->seqnum_min - udev_queue_export->seqnum_max;
 156         if (range - 1 > INT_MAX) {
 157                 err(udev_queue_export->udev, "queue file overflow\n");
 158                 return NULL;
 159         }
 160         devpaths = calloc(1, sizeof(struct queue_devpaths) + (range + 1) * sizeof(long));
 161         if (devpaths == NULL)
 162                 return NULL;
 163         devpaths->devpaths_size = range + 1;
 164
 165         /* read all records and populate the table */
 166         while(1) {
 167                 if (udev_queue_read_seqnum(udev_queue_export->queue_file, &seqnum) < 0)
 168                         break;
 169                 n = seqnum - udev_queue_export->seqnum_max;
 170                 if (n >= devpaths->devpaths_size)
 171                         goto read_error;
 172
 173                 devpath_offset = ftell(udev_queue_export->queue_file);
 174                 devpath_len = udev_queue_skip_devpath(udev_queue_export->queue_file);
 175                 if (devpath_len < 0)
 176                         goto read_error;
 177
 178                 if (devpath_len > 0)
 179                         devpaths->devpaths[n] = devpath_offset;
 180                 else
 181                         devpaths->devpaths[n] = 0;
 182         }
 183
 184         /* find first queued event */
 185         for (i = 0; i < devpaths->devpaths_size; i++) {
 186                 if (devpaths->devpaths[i] != 0)
 187                         break;
 188         }
 189         devpaths->devpaths_first = i;
 190
 191         return devpaths;
 192
 193 read_error:
 194         err(udev_queue_export->udev, "queue file corrupted\n");
 195         free(devpaths);
 196         return NULL;
 197 }
 198
 199 static int rebuild_queue_file(struct udev_queue_export *udev_queue_export)
 200 {
 201         unsigned long long int seqnum;
 202         struct queue_devpaths *devpaths = NULL;
 203         char filename[UTIL_PATH_SIZE];
 204         char filename_tmp[UTIL_PATH_SIZE];
 205         FILE *new_queue_file = NULL;
 206         unsigned int i;
 207
 208         /* read old queue file */
 209         if (udev_queue_export->queue_file != NULL) {
 210                 dbg(udev_queue_export->udev, "compacting queue file, freeing %d bytes\n",
 211                                                 udev_queue_export->waste_bytes);
 212
 213                 devpaths = build_index(udev_queue_export);
 214                 if (devpaths != NULL)
 215                         udev_queue_export->seqnum_max += devpaths->devpaths_first;
 216         }
 217         if (devpaths == NULL) {
 218                 dbg(udev_queue_export->udev, "creating empty queue file\n");
 219                 udev_queue_export->queued_count = 0;
 220                 udev_queue_export->seqnum_max = udev_queue_export->seqnum_min;
 221         }
 222
 223         /* create new queue file */
 224         util_strscpyl(filename_tmp, sizeof(filename_tmp), udev_get_dev_path(udev_queue_export->udev), "/.udev/queue.tmp", NULL);
 225         new_queue_file = fopen(filename_tmp, "w+");
 226         if (new_queue_file == NULL)
 227                 goto error;
 228         seqnum = udev_queue_export->seqnum_max;
 229         fwrite(&seqnum, 1, sizeof(unsigned long long int), new_queue_file);
 230
 231         /* copy unfinished events only to the new file */
 232         if (devpaths != NULL) {
 233                 for (i = devpaths->devpaths_first; i < devpaths->devpaths_size; i++) {
 234                         char devpath[UTIL_PATH_SIZE];
 235                         int err;
 236                         unsigned short devpath_len;
 237
 238                         if (devpaths->devpaths[i] != 0)
 239                         {
 240                                 skip_to(udev_queue_export->queue_file, devpaths->devpaths[i]);
 241                                 err = udev_queue_read_devpath(udev_queue_export->queue_file, devpath, sizeof(devpath));
 242                                 devpath_len = err;
 243
 244                                 fwrite(&seqnum, sizeof(unsigned long long int), 1, new_queue_file);
 245                                 fwrite(&devpath_len, sizeof(unsigned short), 1, new_queue_file);
 246                                 fwrite(devpath, 1, devpath_len, new_queue_file);
 247                         }
 248                         seqnum++;
 249                 }
 250                 free(devpaths);
 251                 devpaths = NULL;
 252         }
 253         fflush(new_queue_file);
 254         if (ferror(new_queue_file))
 255                 goto error;
 256
 257         /* rename the new file on top of the old one */
 258         util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev_queue_export->udev), "/.udev/queue.bin", NULL);
 259         if (rename(filename_tmp, filename) != 0)
 260                 goto error;
 261
 262         if (udev_queue_export->queue_file != NULL)
 263                 fclose(udev_queue_export->queue_file);
 264         udev_queue_export->queue_file = new_queue_file;
 265         udev_queue_export->waste_bytes = 0;
 266
 267         return 0;
 268
 269 error:
 270         err(udev_queue_export->udev, "failed to create queue file: %m\n");
 271         udev_queue_export_cleanup(udev_queue_export);
 272
 273         if (udev_queue_export->queue_file != NULL) {
 274                 fclose(udev_queue_export->queue_file);
 275                 udev_queue_export->queue_file = NULL;
 276         }
 277         if (new_queue_file != NULL)
 278                 fclose(new_queue_file);
 279
 280         if (devpaths != NULL)
 281                 free(devpaths);
 282         udev_queue_export->queued_count = 0;
 283         udev_queue_export->waste_bytes = 0;
 284         udev_queue_export->seqnum_max = udev_queue_export->seqnum_min;
 285
 286         return -1;
 287 }
 288
 289 static int write_queue_record(struct udev_queue_export *udev_queue_export,
 290                               unsigned long long int seqnum, const char *devpath, size_t devpath_len)
 291 {
 292         unsigned short len;
 293
 294         if (udev_queue_export->queue_file == NULL) {
 295                 dbg(udev_queue_export->udev, "can't record event: queue file not available\n");
 296                 return -1;
 297         }
 298
 299         if (fwrite(&seqnum, sizeof(unsigned long long int), 1, udev_queue_export->queue_file) != 1)
 300                 goto write_error;
 301
 302         len = (devpath_len < USHRT_MAX) ? devpath_len : USHRT_MAX;
 303         if (fwrite(&len, sizeof(unsigned short), 1, udev_queue_export->queue_file) != 1)
 304                 goto write_error;
 305         if (fwrite(devpath, 1, len, udev_queue_export->queue_file) != len)
 306                 goto write_error;
 307
 308         /* *must* flush output; caller may fork */
 309         if (fflush(udev_queue_export->queue_file) != 0)
 310                 goto write_error;
 311
 312         return 0;
 313
 314 write_error:
 315         /* if we failed half way through writing a record to a file,
 316            we should not try to write any further records to it. */
 317         err(udev_queue_export->udev, "error writing to queue file: %m\n");
 318         fclose(udev_queue_export->queue_file);
 319         udev_queue_export->queue_file = NULL;
 320
 321         return -1;
 322 }
 323
 324 enum device_state {
 325         DEVICE_QUEUED,
 326         DEVICE_FINISHED,
 327         DEVICE_FAILED,
 328 };
 329
 330 static inline size_t queue_record_size(size_t devpath_len)
 331 {
 332         return sizeof(unsigned long long int) + sizeof(unsigned short int) + devpath_len;
 333 }
 334
 335 static int update_queue(struct udev_queue_export *udev_queue_export,
 336                          struct udev_device *udev_device, enum device_state state)
 337 {
 338         unsigned long long int seqnum = udev_device_get_seqnum(udev_device);
 339         const char *devpath = NULL;
 340         size_t devpath_len = 0;
 341         int bytes;
 342         int err;
 343
 344         if (state == DEVICE_QUEUED) {
 345                 devpath = udev_device_get_devpath(udev_device);
 346                 devpath_len = strlen(devpath);
 347         }
 348
 349         /* recover from an earlier failed rebuild */
 350         if (udev_queue_export->queue_file == NULL) {
 351                 if (rebuild_queue_file(udev_queue_export) != 0)
 352                         return -1;
 353         }
 354
 355         /* when the queue file grows too large, garbage-collect and rebuild it */
 356         bytes = ftell(udev_queue_export->queue_file) + queue_record_size(devpath_len);
 357
 358         /* if we're removing the last event from the queue, that's the best time to rebuild it */
 359         if (state != DEVICE_QUEUED && udev_queue_export->queued_count == 1 && bytes > 2048) {
 360                 /* because we don't need to read the old queue file */
 361                 fclose(udev_queue_export->queue_file);
 362                 udev_queue_export->queue_file = NULL;
 363                 rebuild_queue_file(udev_queue_export);
 364                 return 0;
 365         }
 366
 367         /* try to rebuild the queue files before they grow larger than one page. */
 368         if ((udev_queue_export->waste_bytes > bytes / 2) && bytes > 4096)
 369                 rebuild_queue_file(udev_queue_export);
 370
 371         /* don't record a finished event, if we already dropped the event in a failed rebuild */
 372         if (seqnum < udev_queue_export->seqnum_max)
 373                 return 0;
 374
 375         /* now write to the queue */
 376         if (state == DEVICE_QUEUED) {
 377                 udev_queue_export->queued_count++;
 378                 udev_queue_export->seqnum_min = seqnum;
 379         } else {
 380                 udev_queue_export->waste_bytes += queue_record_size(devpath_len) + queue_record_size(0);
 381                 udev_queue_export->queued_count--;
 382         }
 383         err = write_queue_record(udev_queue_export, seqnum, devpath, devpath_len);
 384
 385         /* try to handle ENOSPC */
 386         if (err != 0 && udev_queue_export->queued_count == 0) {
 387                 udev_queue_export_cleanup(udev_queue_export);
 388                 err = rebuild_queue_file(udev_queue_export);
 389         }
 390
 391         return err;
 392 }
 393
 394 static void update_failed(struct udev_queue_export *udev_queue_export,
 395                           struct udev_device *udev_device, enum device_state state)
 396 {
 397         struct udev *udev = udev_device_get_udev(udev_device);
 398         char filename[UTIL_PATH_SIZE];
 399
 400         if (state != DEVICE_FAILED && udev_queue_export->failed_count == 0)
 401                 return;
 402
 403         /* location of failed file */
 404         util_strscpyl(filename, sizeof(filename), udev_get_dev_path(udev), "/.udev/failed/",
 405                       udev_device_get_subsystem(udev_device), ":", udev_device_get_sysname(udev_device), NULL);
 406
 407         switch (state) {
 408         case DEVICE_FAILED:
 409                 /* record event in the failed directory */
 410                 udev_queue_export->failed_count++;
 411                 util_create_path(udev, filename);
 412                 udev_selinux_setfscreatecon(udev, filename, S_IFLNK);
 413                 symlink(udev_device_get_devpath(udev_device), filename);
 414                 udev_selinux_resetfscreatecon(udev);
 415                 break;
 416
 417         case DEVICE_QUEUED:
 418                 /* delete failed file */
 419                 if (unlink(filename) == 0) {
 420                         util_delete_path(udev, filename);
 421                         udev_queue_export->failed_count--;
 422                 }
 423                 break;
 424
 425         case DEVICE_FINISHED:
 426                 if (udev_device_get_sysname_old(udev_device) != NULL &&
 427                     strcmp(udev_device_get_sysname_old(udev_device), udev_device_get_sysname(udev_device)) != 0) {
 428                         /* "move" event - rename failed file to current name, do not delete failed */
 429                         char filename_old[UTIL_PATH_SIZE];
 430
 431                         util_strscpyl(filename_old, sizeof(filename_old), udev_get_dev_path(udev), "/.udev/failed/",
 432                                       udev_device_get_subsystem(udev_device), ":", udev_device_get_sysname_old(udev_device), NULL);
 433                         if (rename(filename_old, filename) == 0)
 434                                 info(udev, "renamed devpath, moved failed state of '%s' to %s'\n",
 435                                      udev_device_get_devpath_old(udev_device), udev_device_get_devpath(udev_device));
 436                 }
 437                 break;
 438         }
 439
 440         return;
 441 }
 442
 443 static int update(struct udev_queue_export *udev_queue_export,
 444                   struct udev_device *udev_device, enum device_state state)
 445 {
 446         update_failed(udev_queue_export, udev_device, state);
 447
 448         if (update_queue(udev_queue_export, udev_device, state) != 0)
 449                 return -1;
 450
 451         return 0;
 452 }
 453
 454 int udev_queue_export_device_queued(struct udev_queue_export *udev_queue_export, struct udev_device *udev_device)
 455 {
 456         return update(udev_queue_export, udev_device, DEVICE_QUEUED);
 457 }
 458
 459 int udev_queue_export_device_finished(struct udev_queue_export *udev_queue_export, struct udev_device *udev_device)
 460 {
 461         return update(udev_queue_export, udev_device, DEVICE_FINISHED);
 462 }
 463
 464 int udev_queue_export_device_failed(struct udev_queue_export *udev_queue_export, struct udev_device *udev_device)
 465 {
 466         return update(udev_queue_export, udev_device, DEVICE_FAILED);
 467 }