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 unsigned int 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         char buffer[256];
 166         int n;
 167
 168         //_enter(",,%zu,", buflen);
 169
 170         if (!test_bit(CACHEFILES_READY, &cache->flags))
 171                 return 0;
 172
 173         /* check how much space the cache has */
 174         cachefiles_has_space(cache, 0, 0);
 175
 176         /* summarise */
 177         clear_bit(CACHEFILES_STATE_CHANGED, &cache->flags);
 178
 179         n = snprintf(buffer, sizeof(buffer),
 180                      "cull=%c"
 181                      " frun=%llx"
 182                      " fcull=%llx"
 183                      " fstop=%llx"
 184                      " brun=%llx"
 185                      " bcull=%llx"
 186                      " bstop=%llx",
 187                      test_bit(CACHEFILES_CULLING, &cache->flags) ? '1' : '0',
 188                      (unsigned long long) cache->frun,
 189                      (unsigned long long) cache->fcull,
 190                      (unsigned long long) cache->fstop,
 191                      (unsigned long long) cache->brun,
 192                      (unsigned long long) cache->bcull,
 193                      (unsigned long long) cache->bstop
 194                      );
 195
 196         if (n > buflen)
 197                 return -EMSGSIZE;
 198
 199         if (copy_to_user(_buffer, buffer, n) != 0)
 200                 return -EFAULT;
 201
 202         return n;
 203 }
 204
 205 /*
 206  * command the cache
 207  */
 208 static ssize_t cachefiles_daemon_write(struct file *file,
 209                                        const char __user *_data,
 210                                        size_t datalen,
 211                                        loff_t *pos)
 212 {
 213         const struct cachefiles_daemon_cmd *cmd;
 214         struct cachefiles_cache *cache = file->private_data;
 215         ssize_t ret;
 216         char *data, *args, *cp;
 217
 218         //_enter(",,%zu,", datalen);
 219
 220         ASSERT(cache);
 221
 222         if (test_bit(CACHEFILES_DEAD, &cache->flags))
 223                 return -EIO;
 224
 225         if (datalen < 0 || datalen > PAGE_SIZE - 1)
 226                 return -EOPNOTSUPP;
 227
 228         /* drag the command string into the kernel so we can parse it */
 229         data = kmalloc(datalen + 1, GFP_KERNEL);
 230         if (!data)
 231                 return -ENOMEM;
 232
 233         ret = -EFAULT;
 234         if (copy_from_user(data, _data, datalen) != 0)
 235                 goto error;
 236
 237         data[datalen] = '\0';
 238
 239         ret = -EINVAL;
 240         if (memchr(data, '\0', datalen))
 241                 goto error;
 242
 243         /* strip any newline */
 244         cp = memchr(data, '\n', datalen);
 245         if (cp) {
 246                 if (cp == data)
 247                         goto error;
 248
 249                 *cp = '\0';
 250         }
 251
 252         /* parse the command */
 253         ret = -EOPNOTSUPP;
 254
 255         for (args = data; *args; args++)
 256                 if (isspace(*args))
 257                         break;
 258         if (*args) {
 259                 if (args == data)
 260                         goto error;
 261                 *args = '\0';
 262                 args = skip_spaces(++args);
 263         }
 264
 265         /* run the appropriate command handler */
 266         for (cmd = cachefiles_daemon_cmds; cmd->name[0]; cmd++)
 267                 if (strcmp(cmd->name, data) == 0)
 268                         goto found_command;
 269
 270 error:
 271         kfree(data);
 272         //_leave(" = %zd", ret);
 273         return ret;
 274
 275 found_command:
 276         mutex_lock(&cache->daemon_mutex);
 277
 278         ret = -EIO;
 279         if (!test_bit(CACHEFILES_DEAD, &cache->flags))
 280                 ret = cmd->handler(cache, args);
 281
 282         mutex_unlock(&cache->daemon_mutex);
 283
 284         if (ret == 0)
 285                 ret = datalen;
 286         goto error;
 287 }
 288
 289 /*
 290  * poll for culling state
 291  * - use POLLOUT to indicate culling state
 292  */
 293 static unsigned int cachefiles_daemon_poll(struct file *file,
 294                                            struct poll_table_struct *poll)
 295 {
 296         struct cachefiles_cache *cache = file->private_data;
 297         unsigned int mask;
 298
 299         poll_wait(file, &cache->daemon_pollwq, poll);
 300         mask = 0;
 301
 302         if (test_bit(CACHEFILES_STATE_CHANGED, &cache->flags))
 303                 mask |= POLLIN;
 304
 305         if (test_bit(CACHEFILES_CULLING, &cache->flags))
 306                 mask |= POLLOUT;
 307
 308         return mask;
 309 }
 310
 311 /*
 312  * give a range error for cache space constraints
 313  * - can be tail-called
 314  */
 315 static int cachefiles_daemon_range_error(struct cachefiles_cache *cache,
 316                                          char *args)
 317 {
 318         pr_err("Free space limits must be in range 0%%<=stop<cull<run<100%%\n");
 319
 320         return -EINVAL;
 321 }
 322
 323 /*
 324  * set the percentage of files at which to stop culling
 325  * - command: "frun <N>%"
 326  */
 327 static int cachefiles_daemon_frun(struct cachefiles_cache *cache, char *args)
 328 {
 329         unsigned long frun;
 330
 331         _enter(",%s", args);
 332
 333         if (!*args)
 334                 return -EINVAL;
 335
 336         frun = simple_strtoul(args, &args, 10);
 337         if (args[0] != '%' || args[1] != '\0')
 338                 return -EINVAL;
 339
 340         if (frun <= cache->fcull_percent || frun >= 100)
 341                 return cachefiles_daemon_range_error(cache, args);
 342
 343         cache->frun_percent = frun;
 344         return 0;
 345 }
 346
 347 /*
 348  * set the percentage of files at which to start culling
 349  * - command: "fcull <N>%"
 350  */
 351 static int cachefiles_daemon_fcull(struct cachefiles_cache *cache, char *args)
 352 {
 353         unsigned long fcull;
 354
 355         _enter(",%s", args);
 356
 357         if (!*args)
 358                 return -EINVAL;
 359
 360         fcull = simple_strtoul(args, &args, 10);
 361         if (args[0] != '%' || args[1] != '\0')
 362                 return -EINVAL;
 363
 364         if (fcull <= cache->fstop_percent || fcull >= cache->frun_percent)
 365                 return cachefiles_daemon_range_error(cache, args);
 366
 367         cache->fcull_percent = fcull;
 368         return 0;
 369 }
 370
 371 /*
 372  * set the percentage of files at which to stop allocating
 373  * - command: "fstop <N>%"
 374  */
 375 static int cachefiles_daemon_fstop(struct cachefiles_cache *cache, char *args)
 376 {
 377         unsigned long fstop;
 378
 379         _enter(",%s", args);
 380
 381         if (!*args)
 382                 return -EINVAL;
 383
 384         fstop = simple_strtoul(args, &args, 10);
 385         if (args[0] != '%' || args[1] != '\0')
 386                 return -EINVAL;
 387
 388         if (fstop < 0 || fstop >= cache->fcull_percent)
 389                 return cachefiles_daemon_range_error(cache, args);
 390
 391         cache->fstop_percent = fstop;
 392         return 0;
 393 }
 394
 395 /*
 396  * set the percentage of blocks at which to stop culling
 397  * - command: "brun <N>%"
 398  */
 399 static int cachefiles_daemon_brun(struct cachefiles_cache *cache, char *args)
 400 {
 401         unsigned long brun;
 402
 403         _enter(",%s", args);
 404
 405         if (!*args)
 406                 return -EINVAL;
 407
 408         brun = simple_strtoul(args, &args, 10);
 409         if (args[0] != '%' || args[1] != '\0')
 410                 return -EINVAL;
 411
 412         if (brun <= cache->bcull_percent || brun >= 100)
 413                 return cachefiles_daemon_range_error(cache, args);
 414
 415         cache->brun_percent = brun;
 416         return 0;
 417 }
 418
 419 /*
 420  * set the percentage of blocks at which to start culling
 421  * - command: "bcull <N>%"
 422  */
 423 static int cachefiles_daemon_bcull(struct cachefiles_cache *cache, char *args)
 424 {
 425         unsigned long bcull;
 426
 427         _enter(",%s", args);
 428
 429         if (!*args)
 430                 return -EINVAL;
 431
 432         bcull = simple_strtoul(args, &args, 10);
 433         if (args[0] != '%' || args[1] != '\0')
 434                 return -EINVAL;
 435
 436         if (bcull <= cache->bstop_percent || bcull >= cache->brun_percent)
 437                 return cachefiles_daemon_range_error(cache, args);
 438
 439         cache->bcull_percent = bcull;
 440         return 0;
 441 }
 442
 443 /*
 444  * set the percentage of blocks at which to stop allocating
 445  * - command: "bstop <N>%"
 446  */
 447 static int cachefiles_daemon_bstop(struct cachefiles_cache *cache, char *args)
 448 {
 449         unsigned long bstop;
 450
 451         _enter(",%s", args);
 452
 453         if (!*args)
 454                 return -EINVAL;
 455
 456         bstop = simple_strtoul(args, &args, 10);
 457         if (args[0] != '%' || args[1] != '\0')
 458                 return -EINVAL;
 459
 460         if (bstop < 0 || bstop >= cache->bcull_percent)
 461                 return cachefiles_daemon_range_error(cache, args);
 462
 463         cache->bstop_percent = bstop;
 464         return 0;
 465 }
 466
 467 /*
 468  * set the cache directory
 469  * - command: "dir <name>"
 470  */
 471 static int cachefiles_daemon_dir(struct cachefiles_cache *cache, char *args)
 472 {
 473         char *dir;
 474
 475         _enter(",%s", args);
 476
 477         if (!*args) {
 478                 pr_err("Empty directory specified\n");
 479                 return -EINVAL;
 480         }
 481
 482         if (cache->rootdirname) {
 483                 pr_err("Second cache directory specified\n");
 484                 return -EEXIST;
 485         }
 486
 487         dir = kstrdup(args, GFP_KERNEL);
 488         if (!dir)
 489                 return -ENOMEM;
 490
 491         cache->rootdirname = dir;
 492         return 0;
 493 }
 494
 495 /*
 496  * set the cache security context
 497  * - command: "secctx <ctx>"
 498  */
 499 static int cachefiles_daemon_secctx(struct cachefiles_cache *cache, char *args)
 500 {
 501         char *secctx;
 502
 503         _enter(",%s", args);
 504
 505         if (!*args) {
 506                 pr_err("Empty security context specified\n");
 507                 return -EINVAL;
 508         }
 509
 510         if (cache->secctx) {
 511                 pr_err("Second security context specified\n");
 512                 return -EINVAL;
 513         }
 514
 515         secctx = kstrdup(args, GFP_KERNEL);
 516         if (!secctx)
 517                 return -ENOMEM;
 518
 519         cache->secctx = secctx;
 520         return 0;
 521 }
 522
 523 /*
 524  * set the cache tag
 525  * - command: "tag <name>"
 526  */
 527 static int cachefiles_daemon_tag(struct cachefiles_cache *cache, char *args)
 528 {
 529         char *tag;
 530
 531         _enter(",%s", args);
 532
 533         if (!*args) {
 534                 pr_err("Empty tag specified\n");
 535                 return -EINVAL;
 536         }
 537
 538         if (cache->tag)
 539                 return -EEXIST;
 540
 541         tag = kstrdup(args, GFP_KERNEL);
 542         if (!tag)
 543                 return -ENOMEM;
 544
 545         cache->tag = tag;
 546         return 0;
 547 }
 548
 549 /*
 550  * request a node in the cache be culled from the current working directory
 551  * - command: "cull <name>"
 552  */
 553 static int cachefiles_daemon_cull(struct cachefiles_cache *cache, char *args)
 554 {
 555         struct path path;
 556         const struct cred *saved_cred;
 557         int ret;
 558
 559         _enter(",%s", args);
 560
 561         if (strchr(args, '/'))
 562                 goto inval;
 563
 564         if (!test_bit(CACHEFILES_READY, &cache->flags)) {
 565                 pr_err("cull applied to unready cache\n");
 566                 return -EIO;
 567         }
 568
 569         if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
 570                 pr_err("cull applied to dead cache\n");
 571                 return -EIO;
 572         }
 573
 574         /* extract the directory dentry from the cwd */
 575         get_fs_pwd(current->fs, &path);
 576
 577         if (!S_ISDIR(path.dentry->d_inode->i_mode))
 578                 goto notdir;
 579
 580         cachefiles_begin_secure(cache, &saved_cred);
 581         ret = cachefiles_cull(cache, path.dentry, args);
 582         cachefiles_end_secure(cache, saved_cred);
 583
 584         path_put(&path);
 585         _leave(" = %d", ret);
 586         return ret;
 587
 588 notdir:
 589         path_put(&path);
 590         pr_err("cull command requires dirfd to be a directory\n");
 591         return -ENOTDIR;
 592
 593 inval:
 594         pr_err("cull command requires dirfd and filename\n");
 595         return -EINVAL;
 596 }
 597
 598 /*
 599  * set debugging mode
 600  * - command: "debug <mask>"
 601  */
 602 static int cachefiles_daemon_debug(struct cachefiles_cache *cache, char *args)
 603 {
 604         unsigned long mask;
 605
 606         _enter(",%s", args);
 607
 608         mask = simple_strtoul(args, &args, 0);
 609         if (args[0] != '\0')
 610                 goto inval;
 611
 612         cachefiles_debug = mask;
 613         _leave(" = 0");
 614         return 0;
 615
 616 inval:
 617         pr_err("debug command requires mask\n");
 618         return -EINVAL;
 619 }
 620
 621 /*
 622  * find out whether an object in the current working directory is in use or not
 623  * - command: "inuse <name>"
 624  */
 625 static int cachefiles_daemon_inuse(struct cachefiles_cache *cache, char *args)
 626 {
 627         struct path path;
 628         const struct cred *saved_cred;
 629         int ret;
 630
 631         //_enter(",%s", args);
 632
 633         if (strchr(args, '/'))
 634                 goto inval;
 635
 636         if (!test_bit(CACHEFILES_READY, &cache->flags)) {
 637                 pr_err("inuse applied to unready cache\n");
 638                 return -EIO;
 639         }
 640
 641         if (test_bit(CACHEFILES_DEAD, &cache->flags)) {
 642                 pr_err("inuse applied to dead cache\n");
 643                 return -EIO;
 644         }
 645
 646         /* extract the directory dentry from the cwd */
 647         get_fs_pwd(current->fs, &path);
 648
 649         if (!S_ISDIR(path.dentry->d_inode->i_mode))
 650                 goto notdir;
 651
 652         cachefiles_begin_secure(cache, &saved_cred);
 653         ret = cachefiles_check_in_use(cache, path.dentry, args);
 654         cachefiles_end_secure(cache, saved_cred);
 655
 656         path_put(&path);
 657         //_leave(" = %d", ret);
 658         return ret;
 659
 660 notdir:
 661         path_put(&path);
 662         pr_err("inuse command requires dirfd to be a directory\n");
 663         return -ENOTDIR;
 664
 665 inval:
 666         pr_err("inuse command requires dirfd and filename\n");
 667         return -EINVAL;
 668 }
 669
 670 /*
 671  * see if we have space for a number of pages and/or a number of files in the
 672  * cache
 673  */
 674 int cachefiles_has_space(struct cachefiles_cache *cache,
 675                          unsigned fnr, unsigned bnr)
 676 {
 677         struct kstatfs stats;
 678         struct path path = {
 679                 .mnt    = cache->mnt,
 680                 .dentry = cache->mnt->mnt_root,
 681         };
 682         int ret;
 683
 684         //_enter("{%llu,%llu,%llu,%llu,%llu,%llu},%u,%u",
 685         //       (unsigned long long) cache->frun,
 686         //       (unsigned long long) cache->fcull,
 687         //       (unsigned long long) cache->fstop,
 688         //       (unsigned long long) cache->brun,
 689         //       (unsigned long long) cache->bcull,
 690         //       (unsigned long long) cache->bstop,
 691         //       fnr, bnr);
 692
 693         /* find out how many pages of blockdev are available */
 694         memset(&stats, 0, sizeof(stats));
 695
 696         ret = vfs_statfs(&path, &stats);
 697         if (ret < 0) {
 698                 if (ret == -EIO)
 699                         cachefiles_io_error(cache, "statfs failed");
 700                 _leave(" = %d", ret);
 701                 return ret;
 702         }
 703
 704         stats.f_bavail >>= cache->bshift;
 705
 706         //_debug("avail %llu,%llu",
 707         //       (unsigned long long) stats.f_ffree,
 708         //       (unsigned long long) stats.f_bavail);
 709
 710         /* see if there is sufficient space */
 711         if (stats.f_ffree > fnr)
 712                 stats.f_ffree -= fnr;
 713         else
 714                 stats.f_ffree = 0;
 715
 716         if (stats.f_bavail > bnr)
 717                 stats.f_bavail -= bnr;
 718         else
 719                 stats.f_bavail = 0;
 720
 721         ret = -ENOBUFS;
 722         if (stats.f_ffree < cache->fstop ||
 723             stats.f_bavail < cache->bstop)
 724                 goto begin_cull;
 725
 726         ret = 0;
 727         if (stats.f_ffree < cache->fcull ||
 728             stats.f_bavail < cache->bcull)
 729                 goto begin_cull;
 730
 731         if (test_bit(CACHEFILES_CULLING, &cache->flags) &&
 732             stats.f_ffree >= cache->frun &&
 733             stats.f_bavail >= cache->brun &&
 734             test_and_clear_bit(CACHEFILES_CULLING, &cache->flags)
 735             ) {
 736                 _debug("cease culling");
 737                 cachefiles_state_changed(cache);
 738         }
 739
 740         //_leave(" = 0");
 741         return 0;
 742
 743 begin_cull:
 744         if (!test_and_set_bit(CACHEFILES_CULLING, &cache->flags)) {
 745                 _debug("### CULL CACHE ###");
 746                 cachefiles_state_changed(cache);
 747         }
 748
 749         _leave(" = %d", ret);
 750         return ret;
 751 }