fs/cachefiles/daemon.c

   1 /* Daemon interface
   2  *
   3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #include <linux/module.h>
  13 #include <linux/init.h>
  14 #include <linux/sched.h>
  15 #include <linux/completion.h>
  16 #include <linux/slab.h>
  17 #include <linux/fs.h>
  18 #include <linux/file.h>
  19 #include <linux/namei.h>
  20 #include <linux/poll.h>
  21 #include <linux/mount.h>
  22 #include <linux/statfs.h>
  23 #include <linux/ctype.h>
  24 #include <linux/string.h>
  25 #include <linux/fs_struct.h>
  26 #include "internal.h"
  27
  28 static int cachefiles_daemon_open(struct inode *, struct file *);
  29 static int cachefiles_daemon_release(struct inode *, struct file *);
  30 static ssize_t cachefiles_daemon_read(struct file *, char __user *, size_t,
  31                                       loff_t *);
  32 static ssize_t cachefiles_daemon_write(struct file *, const char __user *,
  33                                        size_t, loff_t *);
  34 static __poll_t cachefiles_daemon_poll(struct file *,
  35                                            struct poll_table_struct *);
  36 static int cachefiles_daemon_frun(struct cachefiles_cache *, char *);
  37 static int cachefiles_daemon_fcull(struct cachefiles_cache *, char *);
  38 static int cachefiles_daemon_fstop(struct cachefiles_cache *, char *);
  39 static int cachefiles_daemon_brun(struct cachefiles_cache *, char *);
  40 static int cachefiles_daemon_bcull(struct cachefiles_cache *, char *);
  41 static int cachefiles_daemon_bstop(struct cachefiles_cache *, char *);
  42 static int cachefiles_daemon_cull(struct cachefiles_cache *, char *);
  43 static int cachefiles_daemon_debug(struct cachefiles_cache *, char *);
  44 static int cachefiles_daemon_dir(struct cachefiles_cache *, char *);
  45 static int cachefiles_daemon_inuse(struct cachefiles_cache *, char *);
  46 static int cachefiles_daemon_secctx(struct cachefiles_cache *, char *);
  47 static int cachefiles_daemon_tag(struct cachefiles_cache *, char *);
  48
  49 static unsigned long cachefiles_open;
  50
  51 const struct file_operations cachefiles_daemon_fops = {
  52         .owner          = THIS_MODULE,
  53         .open           = cachefiles_daemon_open,
  54         .release        = cachefiles_daemon_release,
  55         .read           = cachefiles_daemon_read,
  56         .write          = cachefiles_daemon_write,
  57         .poll           = cachefiles_daemon_poll,
  58         .llseek         = noop_llseek,
  59 };
  60
  61 struct cachefiles_daemon_cmd {
  62         char name[8];
  63         int (*handler)(struct cachefiles_cache *cache, char *args);
  64 };
  65
  66 static const struct cachefiles_daemon_cmd cachefiles_daemon_cmds[] = {
  67         { "bind",       cachefiles_daemon_bind          },
  68         { "brun",       cachefiles_daemon_brun          },
  69         { "bcull",      cachefiles_daemon_bcull         },
  70         { "bstop",      cachefiles_daemon_bstop         },
  71         { "cull",       cachefiles_daemon_cull          },
  72         { "debug",      cachefiles_daemon_debug         },
  73         { "dir",        cachefiles_daemon_dir           },
  74         { "frun",       cachefiles_daemon_frun          },
  75         { "fcull",      cachefiles_daemon_fcull         },
  76         { "fstop",      cachefiles_daemon_fstop         },
  77         { "inuse",      cachefiles_daemon_inuse         },
  78         { "secctx",     cachefiles_daemon_secctx        },
  79         { "tag",        cachefiles_daemon_tag           },
  80         { "",           NULL                            }
  81 };
  82
  83
  84 /*
  85  * do various checks
  86  */
  87 static int cachefiles_daemon_open(struct inode *inode, struct file *file)
  88 {
  89         struct cachefiles_cache *cache;
  90
  91         _enter("");
  92
  93         /* only the superuser may do this */
  94         if (!capable(CAP_SYS_ADMIN))
  95                 return -EPERM;
  96
  97         /* the cachefiles device may only be open once at a time */
  98         if (xchg(&cachefiles_open, 1) == 1)
  99                 return -EBUSY;
 100
 101         /* allocate a cache record */
 102         cache = kzalloc(sizeof(struct cachefiles_cache), GFP_KERNEL);
 103         if (!cache) {
 104                 cachefiles_open = 0;
 105                 return -ENOMEM;
 106         }
 107
 108         mutex_init(&cache->daemon_mutex);
 109         cache->active_nodes = RB_ROOT;
 110         rwlock_init(&cache->active_lock);
 111         init_waitqueue_head(&cache->daemon_pollwq);
 112
 113         /* set default caching limits
 114          * - limit at 1% free space and/or free files
 115          * - cull below 5% free space and/or free files
 116          * - cease culling above 7% free space and/or free files
 117          */
 118         cache->frun_percent = 7;
 119         cache->fcull_percent = 5;
 120         cache->fstop_percent = 1;
 121         cache->brun_percent = 7;
 122         cache->bcull_percent = 5;
 123         cache->bstop_percent = 1;
 124
 125         file->private_data = cache;
 126         cache->cachefilesd = file;
 127         return 0;
 128 }
 129
 130 /*
 131  * release a cache
 132  */
 133 static int cachefiles_daemon_release(struct inode *inode, struct file *file)
 134 {
 135         struct cachefiles_cache *cache = file->private_data;
 136
 137         _enter("");
 138
 139         ASSERT(cache);
 140
 141         set_bit(CACHEFILES_DEAD, &cache->flags);
 142
 143         cachefiles_daemon_unbind(cache);
 144
 145         ASSERT(!cache->active_nodes.rb_node);
 146
 147         /* clean up the control file interface */
 148         cache->cachefilesd = NULL;
 149         file->private_data = NULL;
 150         cachefiles_open = 0;
 151
 152         kfree(cache);
 153
 154         _leave("");
 155         return 0;
 156 }
 157
 158 /*
 159  * read the cache state
 160  */
 161 static ssize_t cachefiles_daemon_read(struct file *file, char __user *_buffer,
 162                                       size_t buflen, loff_t *pos)
 163 {
 164         struct cachefiles_cache *cache = file->private_data;
 165         unsigned long long b_released;
 166         unsigned f_released;
 167         char buffer[256];
 168         int n;
 169
 170         //_enter(",,%zu,", buflen);
 171
 172         if (!test_bit(CACHEFILES_READY, &cache->flags))
 173                 return 0;
 174
 175         /* check how much space the cache has */
 176         cachefiles_has_space(cache, 0, 0);
 177
 178         /* summarise */
 179         f_released = atomic_xchg(&cache->f_released, 0);
 180         b_released = atomic_long_xchg(&cache->b_released, 0);
 181         clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
 182
 183         n = snprintf(buffer, sizeof(buffer),
 184                      "cull=%c"
 185                      " frun=%llx"
 186                      " fcull=%llx"
 187                      " fstop=%llx"
 188                      " brun=%llx"
 189                      " bcull=%llx"
 190                      " bstop=%llx"
 191                      " freleased=%x"
 192                      " breleased=%llx",
 193                      test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
 194                      (unsigned long long) cache->frun,
 195                      (unsigned long long) cache->fcull,
 196                      (unsigned long long) cache->fstop,
 197                      (unsigned long long) cache->brun,
 198                      (unsigned long long) cache->bcull,
 199                      (unsigned long long) cache->bstop,
 200                      f_released,
 201                      b_released);
 202
 203         if (n > buflen)
 204                 return -EMSGSIZE;
 205
 206         if (copy_to_user(_buffer, buffer, n) != 0)
 207                 return -EFAULT;
 208
 209         return n;
 210 }
 211
 212 /*
 213  * command the cache
 214  */
 215 static ssize_t cachefiles_daemon_write(struct file *file,
 216                                        const char __user *_data,
 217                                        size_t datalen,
 218                                        loff_t *pos)
 219 {
 220         const struct cachefiles_daemon_cmd *cmd;
 221         struct cachefiles_cache *cache = file->private_data;
 222         ssize_t ret;
 223         char *data, *args, *cp;
 224
 225         //_enter(",,%zu,", datalen);
 226
 227         ASSERT(cache);
 228
 229         if (test_bit(CACHEFILES_DEAD, &cache->flags))
 230                 return -EIO;
 231
 232         if (datalen < 0 || datalen > PAGE_SIZE - 1)
 233                 return -EOPNOTSUPP;
 234
 235         /* drag the command string into the kernel so we can parse it */
 236         data = memdup_user_nul(_data, datalen);
 237         if (IS_ERR(data))
 238                 return PTR_ERR(data);
 239
 240         ret = -EINVAL;
 241         if (memchr(data, '\0', datalen))
 242                 goto error;
 243
 244         /* strip any newline */
 245         cp = memchr(data, '\n', datalen);
 246         if (cp) {
 247                 if (cp == data)
 248                         goto error;
 249
 250                 *cp = '\0';
 251         }
 252
 253         /* parse the command */
 254         ret = -EOPNOTSUPP;
 255
 256         for (args = data; *args; args++)
 257                 if (isspace(*args))
 258                         break;
 259         if (*args) {
 260                 if (args == data)
 261                         goto error;
 262                 *args = '\0';
 263                 args = skip_spaces(++args);
 264         }
 265
 266         /* run the appropriate command handler */
 267         for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
 268                 if (strcmp(cmd->name, data) == 0)
 269                         goto found_command;
 270
 271 error:
 272         kfree(data);
 273         //_leave(" = %zd", ret);
 274         return ret;
 275
 276 found_command:
 277         mutex_lock(&cache->daemon_mutex);
 278
 279         ret = -EIO;
 280         if (!test_bit(CACHEFILES_DEAD, &cache->flags))
 281                 ret = cmd->handler(cache, args);
 282
 283         mutex_unlock(&cache->daemon_mutex);
 284
 285         if (ret == 0)
 286                 ret = datalen;
 287         goto error;
 288 }
 289
 290 /*
 291  * poll for culling state
 292  * - use EPOLLOUT to indicate culling state
 293  */
 294 static __poll_t cachefiles_daemon_poll(struct file *file,
 295                                            struct poll_table_struct *poll)
 296 {
 297         struct cachefiles_cache *cache = file->private_data;
 298         __poll_t mask;
 299
 300         poll_wait(file, &cache->daemon_pollwq, poll);
 301         mask = 0;
 302
 303         if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
 304                 mask |= EPOLLIN;
 305
 306         if (test_bit(CACHEFILES_CULLING, &cache->flags))
 307                 mask |= EPOLLOUT;
 308
 309         return mask;
 310 }
 311
 312 /*
 313  * give a range error for cache space constraints
 314  * - can be tail-called
 315  */
 316 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
 317                                          char *args)
 318 {
 319         pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
 320
 321         return -EINVAL;
 322 }
 323
 324 /*
 325  * set the percentage of files at which to stop culling
 326  * - command: "frun <N>%"
 327  */
 328 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
 329 {
 330         unsigned long frun;
 331
 332         _enter(",%s", args);
 333
 334         if (!*args)
 335                 return -EINVAL;
 336
 337         frun = simple_strtoul(args, &args, 10);
 338         if (args[0] != '%' || args[1] != '\0')
 339                 return -EINVAL;
 340
 341         if (frun <= cache->fcull_percent || frun >= 100)
 342                 return cachefiles_daemon_range_error(cache, args);
 343
 344         cache->frun_percent = frun;
 345         return 0;
 346 }
 347
 348 /*
 349  * set the percentage of files at which to start culling
 350  * - command: "fcull <N>%"
 351  */
 352 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
 353 {
 354         unsigned long fcull;
 355
 356         _enter(",%s", args);
 357
 358         if (!*args)
 359                 return -EINVAL;
 360
 361         fcull = simple_strtoul(args, &args, 10);
 362         if (args[0] != '%' || args[1] != '\0')
 363                 return -EINVAL;
 364
 365         if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
 366                 return cachefiles_daemon_range_error(cache, args);
 367
 368         cache->fcull_percent = fcull;
 369         return 0;
 370 }
 371
 372 /*
 373  * set the percentage of files at which to stop allocating
 374  * - command: "fstop <N>%"
 375  */
 376 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
 377 {
 378         unsigned long fstop;
 379
 380         _enter(",%s", args);
 381
 382         if (!*args)
 383                 return -EINVAL;
 384
 385         fstop = simple_strtoul(args, &args, 10);
 386         if (args[0] != '%' || args[1] != '\0')
 387                 return -EINVAL;
 388
 389         if (fstop < 0 || fstop >= cache->fcull_percent)
 390                 return cachefiles_daemon_range_error(cache, args);
 391
 392         cache->fstop_percent = fstop;
 393         return 0;
 394 }
 395
 396 /*
 397  * set the percentage of blocks at which to stop culling
 398  * - command: "brun <N>%"
 399  */
 400 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
 401 {
 402         unsigned long brun;
 403
 404         _enter(",%s", args);
 405
 406         if (!*args)
 407                 return -EINVAL;
 408
 409         brun = simple_strtoul(args, &args, 10);
 410         if (args[0] != '%' || args[1] != '\0')
 411                 return -EINVAL;
 412
 413         if (brun <= cache->bcull_percent || brun >= 100)
 414                 return cachefiles_daemon_range_error(cache, args);
 415
 416         cache->brun_percent = brun;
 417         return 0;
 418 }
 419
 420 /*
 421  * set the percentage of blocks at which to start culling
 422  * - command: "bcull <N>%"
 423  */
 424 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
 425 {
 426         unsigned long bcull;
 427
 428         _enter(",%s", args);
 429
 430         if (!*args)
 431                 return -EINVAL;
 432
 433         bcull = simple_strtoul(args, &args, 10);
 434         if (args[0] != '%' || args[1] != '\0')
 435                 return -EINVAL;
 436
 437         if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
 438                 return cachefiles_daemon_range_error(cache, args);
 439
 440         cache->bcull_percent = bcull;
 441         return 0;
 442 }
 443
 444 /*
 445  * set the percentage of blocks at which to stop allocating
 446  * - command: "bstop <N>%"
 447  */
 448 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
 449 {
 450         unsigned long bstop;
 451
 452         _enter(",%s", args);
 453
 454         if (!*args)
 455                 return -EINVAL;
 456
 457         bstop = simple_strtoul(args, &args, 10);
 458         if (args[0] != '%' || args[1] != '\0')
 459                 return -EINVAL;
 460
 461         if (bstop < 0 || bstop >= cache->bcull_percent)
 462                 return cachefiles_daemon_range_error(cache, args);
 463
 464         cache->bstop_percent = bstop;
 465         return 0;
 466 }
 467
 468 /*
 469  * set the cache directory
 470  * - command: "dir <name>"
 471  */
 472 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
 473 {
 474         char *dir;
 475
 476         _enter(",%s", args);
 477
 478         if (!*args) {
 479                 pr_err("Empty directory specified\n");
 480                 return -EINVAL;
 481         }
 482
 483         if (cache->rootdirname) {
 484                 pr_err("Second cache directory specified\n");
 485                 return -EEXIST;
 486         }
 487
 488         dir = kstrdup(args, GFP_KERNEL);
 489         if (!dir)
 490                 return -ENOMEM;
 491
 492         cache->rootdirname = dir;
 493         return 0;
 494 }
 495
 496 /*
 497  * set the cache security context
 498  * - command: "secctx <ctx>"
 499  */
 500 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
 501 {
 502         char *secctx;
 503
 504         _enter(",%s", args);
 505
 506         if (!*args) {
 507                 pr_err("Empty security context specified\n");
 508                 return -EINVAL;
 509         }
 510
 511         if (cache->secctx) {
 512                 pr_err("Second security context specified\n");
 513                 return -EINVAL;
 514         }
 515
 516         secctx = kstrdup(args, GFP_KERNEL);
 517         if (!secctx)
 518                 return -ENOMEM;
 519
 520         cache->secctx = secctx;
 521         return 0;
 522 }
 523
 524 /*
 525  * set the cache tag
 526  * - command: "tag <name>"
 527  */
 528 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
 529 {
 530         char *tag;
 531
 532         _enter(",%s", args);
 533
 534         if (!*args) {
 535                 pr_err("Empty tag specified\n");
 536                 return -EINVAL;
 537         }
 538
 539         if (cache->tag)
 540                 return -EEXIST;
 541
 542         tag = kstrdup(args, GFP_KERNEL);
 543         if (!tag)
 544                 return -ENOMEM;
 545
 546         cache->tag = tag;
 547         return 0;
 548 }
 549
 550 /*
 551  * request a node in the cache be culled from the current working directory
 552  * - command: "cull <name>"
 553  */
 554 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
 555 {
 556         struct path path;
 557         const struct cred *saved_cred;
 558         int ret;
 559
 560         _enter(",%s", args);
 561
 562         if (strchr(args, '/'))
 563                 goto inval;
 564
 565         if (!test_bit(CACHEFILES_READY, &cache->flags)) {
 566                 pr_err("cull applied to unready cache\n");
 567                 return -EIO;
 568         }
 569
 570         if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
 571                 pr_err("cull applied to dead cache\n");
 572                 return -EIO;
 573         }
 574
 575         /* extract the directory dentry from the cwd */
 576         get_fs_pwd(current->fs, &path);
 577
 578         if (!d_can_lookup(path.dentry))
 579                 goto notdir;
 580
 581         cachefiles_begin_secure(cache, &saved_cred);
 582         ret = cachefiles_cull(cache, path.dentry, args);
 583         cachefiles_end_secure(cache, saved_cred);
 584
 585         path_put(&path);
 586         _leave(" = %d", ret);
 587         return ret;
 588
 589 notdir:
 590         path_put(&path);
 591         pr_err("cull command requires dirfd to be a directory\n");
 592         return -ENOTDIR;
 593
 594 inval:
 595         pr_err("cull command requires dirfd and filename\n");
 596         return -EINVAL;
 597 }
 598
 599 /*
 600  * set debugging mode
 601  * - command: "debug <mask>"
 602  */
 603 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
 604 {
 605         unsigned long mask;
 606
 607         _enter(",%s", args);
 608
 609         mask = simple_strtoul(args, &args, 0);
 610         if (args[0] != '\0')
 611                 goto inval;
 612
 613         cachefiles_debug = mask;
 614         _leave(" = 0");
 615         return 0;
 616
 617 inval:
 618         pr_err("debug command requires mask\n");
 619         return -EINVAL;
 620 }
 621
 622 /*
 623  * find out whether an object in the current working directory is in use or not
 624  * - command: "inuse <name>"
 625  */
 626 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
 627 {
 628         struct path path;
 629         const struct cred *saved_cred;
 630         int ret;
 631
 632         //_enter(",%s", args);
 633
 634         if (strchr(args, '/'))
 635                 goto inval;
 636
 637         if (!test_bit(CACHEFILES_READY, &cache->flags)) {
 638                 pr_err("inuse applied to unready cache\n");
 639                 return -EIO;
 640         }
 641
 642         if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
 643                 pr_err("inuse applied to dead cache\n");
 644                 return -EIO;
 645         }
 646
 647         /* extract the directory dentry from the cwd */
 648         get_fs_pwd(current->fs, &path);
 649
 650         if (!d_can_lookup(path.dentry))
 651                 goto notdir;
 652
 653         cachefiles_begin_secure(cache, &saved_cred);
 654         ret = cachefiles_check_in_use(cache, path.dentry, args);
 655         cachefiles_end_secure(cache, saved_cred);
 656
 657         path_put(&path);
 658         //_leave(" = %d", ret);
 659         return ret;
 660
 661 notdir:
 662         path_put(&path);
 663         pr_err("inuse command requires dirfd to be a directory\n");
 664         return -ENOTDIR;
 665
 666 inval:
 667         pr_err("inuse command requires dirfd and filename\n");
 668         return -EINVAL;
 669 }
 670
 671 /*
 672  * see if we have space for a number of pages and/or a number of files in the
 673  * cache
 674  */
 675 int cachefiles_has_space(struct cachefiles_cache *cache,
 676                          unsigned fnr, unsigned bnr)
 677 {
 678         struct kstatfs stats;
 679         struct path path = {
 680                 .mnt    = cache->mnt,
 681                 .dentry = cache->mnt->mnt_root,
 682         };
 683         int ret;
 684
 685         //_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
 686         //       (unsigned long long) cache->frun,
 687         //       (unsigned long long) cache->fcull,
 688         //       (unsigned long long) cache->fstop,
 689         //       (unsigned long long) cache->brun,
 690         //       (unsigned long long) cache->bcull,
 691         //       (unsigned long long) cache->bstop,
 692         //       fnr, bnr);
 693
 694         /* find out how many pages of blockdev are available */
 695         memset(&stats, 0, sizeof(stats));
 696
 697         ret = vfs_statfs(&path, &stats);
 698         if (ret < 0) {
 699                 if (ret == -EIO)
 700                         cachefiles_io_error(cache, "statfs failed");
 701                 _leave(" = %d", ret);
 702                 return ret;
 703         }
 704
 705         stats.f_bavail >>= cache->bshift;
 706
 707         //_debug("avail %llu,%llu",
 708         //       (unsigned long long) stats.f_ffree,
 709         //       (unsigned long long) stats.f_bavail);
 710
 711         /* see if there is sufficient space */
 712         if (stats.f_ffree > fnr)
 713                 stats.f_ffree -= fnr;
 714         else
 715                 stats.f_ffree = 0;
 716
 717         if (stats.f_bavail > bnr)
 718                 stats.f_bavail -= bnr;
 719         else
 720                 stats.f_bavail = 0;
 721
 722         ret = -ENOBUFS;
 723         if (stats.f_ffree < cache->fstop ||
 724             stats.f_bavail < cache->bstop)
 725                 goto begin_cull;
 726
 727         ret = 0;
 728         if (stats.f_ffree < cache->fcull ||
 729             stats.f_bavail < cache->bcull)
 730                 goto begin_cull;
 731
 732         if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
 733             stats.f_ffree >= cache->frun &&
 734             stats.f_bavail >= cache->brun &&
 735             test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
 736             ) {
 737                 _debug("cease culling");
 738                 cachefiles_state_changed(cache);
 739         }
 740
 741         //_leave(" = 0");
 742         return 0;
 743
 744 begin_cull:
 745         if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
 746                 _debug("### CULL CACHE ###");
 747                 cachefiles_state_changed(cache);
 748         }
 749
 750         _leave(" = %d", ret);
 751         return ret;
 752 }