fs/pstore/platform.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Persistent Storage - platform driver interface parts.
   4  *
   5  * Copyright (C) 2007-2008 Google, Inc.
   6  * Copyright (C) 2010 Intel Corporation <tony.luck@intel.com>
   7  */
   8
   9 #define pr_fmt(fmt) "pstore: " fmt
  10
  11 #include <linux/atomic.h>
  12 #include <linux/types.h>
  13 #include <linux/errno.h>
  14 #include <linux/init.h>
  15 #include <linux/kmsg_dump.h>
  16 #include <linux/console.h>
  17 #include <linux/module.h>
  18 #include <linux/pstore.h>
  19 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
  20 #include <linux/lzo.h>
  21 #endif
  22 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
  23 #include <linux/lz4.h>
  24 #endif
  25 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
  26 #include <linux/zstd.h>
  27 #endif
  28 #include <linux/crypto.h>
  29 #include <linux/string.h>
  30 #include <linux/timer.h>
  31 #include <linux/slab.h>
  32 #include <linux/uaccess.h>
  33 #include <linux/jiffies.h>
  34 #include <linux/workqueue.h>
  35
  36 #include "internal.h"
  37
  38 /*
  39  * We defer making "oops" entries appear in pstore - see
  40  * whether the system is actually still running well enough
  41  * to let someone see the entry
  42  */
  43 static int pstore_update_ms = -1;
  44 module_param_named(update_ms, pstore_update_ms, int, 0600);
  45 MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
  46                  "(default is -1, which means runtime updates are disabled; "
  47                  "enabling this option may not be safe; it may lead to further "
  48                  "corruption on Oopses)");
  49
  50 /* Names should be in the same order as the enum pstore_type_id */
  51 static const char * const pstore_type_names[] = {
  52         "dmesg",
  53         "mce",
  54         "console",
  55         "ftrace",
  56         "rtas",
  57         "powerpc-ofw",
  58         "powerpc-common",
  59         "pmsg",
  60         "powerpc-opal",
  61 };
  62
  63 static int pstore_new_entry;
  64
  65 static void pstore_timefunc(struct timer_list *);
  66 static DEFINE_TIMER(pstore_timer, pstore_timefunc);
  67
  68 static void pstore_dowork(struct work_struct *);
  69 static DECLARE_WORK(pstore_work, pstore_dowork);
  70
  71 /*
  72  * psinfo_lock protects "psinfo" during calls to
  73  * pstore_register(), pstore_unregister(), and
  74  * the filesystem mount/unmount routines.
  75  */
  76 static DEFINE_MUTEX(psinfo_lock);
  77 struct pstore_info *psinfo;
  78
  79 static char *backend;
  80 module_param(backend, charp, 0444);
  81 MODULE_PARM_DESC(backend, "specific backend to use");
  82
  83 static char *compress =
  84 #ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
  85                 CONFIG_PSTORE_COMPRESS_DEFAULT;
  86 #else
  87                 NULL;
  88 #endif
  89 module_param(compress, charp, 0444);
  90 MODULE_PARM_DESC(compress, "compression to use");
  91
  92 /* Compression parameters */
  93 static struct crypto_comp *tfm;
  94
  95 struct pstore_zbackend {
  96         int (*zbufsize)(size_t size);
  97         const char *name;
  98 };
  99
 100 static char *big_oops_buf;
 101 static size_t big_oops_buf_sz;
 102
 103 /* How much of the console log to snapshot */
 104 unsigned long kmsg_bytes = PSTORE_DEFAULT_KMSG_BYTES;
 105
 106 void pstore_set_kmsg_bytes(int bytes)
 107 {
 108         kmsg_bytes = bytes;
 109 }
 110
 111 /* Tag each group of saved records with a sequence number */
 112 static int      oopscount;
 113
 114 const char *pstore_type_to_name(enum pstore_type_id type)
 115 {
 116         BUILD_BUG_ON(ARRAY_SIZE(pstore_type_names) != PSTORE_TYPE_MAX);
 117
 118         if (WARN_ON_ONCE(type >= PSTORE_TYPE_MAX))
 119                 return "unknown";
 120
 121         return pstore_type_names[type];
 122 }
 123 EXPORT_SYMBOL_GPL(pstore_type_to_name);
 124
 125 enum pstore_type_id pstore_name_to_type(const char *name)
 126 {
 127         int i;
 128
 129         for (i = 0; i < PSTORE_TYPE_MAX; i++) {
 130                 if (!strcmp(pstore_type_names[i], name))
 131                         return i;
 132         }
 133
 134         return PSTORE_TYPE_MAX;
 135 }
 136 EXPORT_SYMBOL_GPL(pstore_name_to_type);
 137
 138 static void pstore_timer_kick(void)
 139 {
 140         if (pstore_update_ms < 0)
 141                 return;
 142
 143         mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
 144 }
 145
 146 /*
 147  * Should pstore_dump() wait for a concurrent pstore_dump()? If
 148  * not, the current pstore_dump() will report a failure to dump
 149  * and return.
 150  */
 151 static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
 152 {
 153         /* In NMI path, pstore shouldn't block regardless of reason. */
 154         if (in_nmi())
 155                 return true;
 156
 157         switch (reason) {
 158         /* In panic case, other cpus are stopped by smp_send_stop(). */
 159         case KMSG_DUMP_PANIC:
 160         /* Emergency restart shouldn't be blocked. */
 161         case KMSG_DUMP_EMERG:
 162                 return true;
 163         default:
 164                 return false;
 165         }
 166 }
 167
 168 #if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
 169 static int zbufsize_deflate(size_t size)
 170 {
 171         size_t cmpr;
 172
 173         switch (size) {
 174         /* buffer range for efivars */
 175         case 1000 ... 2000:
 176                 cmpr = 56;
 177                 break;
 178         case 2001 ... 3000:
 179                 cmpr = 54;
 180                 break;
 181         case 3001 ... 3999:
 182                 cmpr = 52;
 183                 break;
 184         /* buffer range for nvram, erst */
 185         case 4000 ... 10000:
 186                 cmpr = 45;
 187                 break;
 188         default:
 189                 cmpr = 60;
 190                 break;
 191         }
 192
 193         return (size * 100) / cmpr;
 194 }
 195 #endif
 196
 197 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
 198 static int zbufsize_lzo(size_t size)
 199 {
 200         return lzo1x_worst_compress(size);
 201 }
 202 #endif
 203
 204 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
 205 static int zbufsize_lz4(size_t size)
 206 {
 207         return LZ4_compressBound(size);
 208 }
 209 #endif
 210
 211 #if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
 212 static int zbufsize_842(size_t size)
 213 {
 214         return size;
 215 }
 216 #endif
 217
 218 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
 219 static int zbufsize_zstd(size_t size)
 220 {
 221         return ZSTD_compressBound(size);
 222 }
 223 #endif
 224
 225 static const struct pstore_zbackend *zbackend __ro_after_init;
 226
 227 static const struct pstore_zbackend zbackends[] = {
 228 #if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
 229         {
 230                 .zbufsize       = zbufsize_deflate,
 231                 .name           = "deflate",
 232         },
 233 #endif
 234 #if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
 235         {
 236                 .zbufsize       = zbufsize_lzo,
 237                 .name           = "lzo",
 238         },
 239 #endif
 240 #if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
 241         {
 242                 .zbufsize       = zbufsize_lz4,
 243                 .name           = "lz4",
 244         },
 245 #endif
 246 #if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
 247         {
 248                 .zbufsize       = zbufsize_lz4,
 249                 .name           = "lz4hc",
 250         },
 251 #endif
 252 #if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
 253         {
 254                 .zbufsize       = zbufsize_842,
 255                 .name           = "842",
 256         },
 257 #endif
 258 #if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
 259         {
 260                 .zbufsize       = zbufsize_zstd,
 261                 .name           = "zstd",
 262         },
 263 #endif
 264         { }
 265 };
 266
 267 static int pstore_compress(const void *in, void *out,
 268                            unsigned int inlen, unsigned int outlen)
 269 {
 270         int ret;
 271
 272         ret = crypto_comp_compress(tfm, in, inlen, out, &outlen);
 273         if (ret) {
 274                 pr_err("crypto_comp_compress failed, ret = %d!\n", ret);
 275                 return ret;
 276         }
 277
 278         return outlen;
 279 }
 280
 281 static void allocate_buf_for_compression(void)
 282 {
 283         struct crypto_comp *ctx;
 284         int size;
 285         char *buf;
 286
 287         /* Skip if not built-in or compression backend not selected yet. */
 288         if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
 289                 return;
 290
 291         /* Skip if no pstore backend yet or compression init already done. */
 292         if (!psinfo || tfm)
 293                 return;
 294
 295         if (!crypto_has_comp(zbackend->name, 0, 0)) {
 296                 pr_err("Unknown compression: %s\n", zbackend->name);
 297                 return;
 298         }
 299
 300         size = zbackend->zbufsize(psinfo->bufsize);
 301         if (size <= 0) {
 302                 pr_err("Invalid compression size for %s: %d\n",
 303                        zbackend->name, size);
 304                 return;
 305         }
 306
 307         buf = kmalloc(size, GFP_KERNEL);
 308         if (!buf) {
 309                 pr_err("Failed %d byte compression buffer allocation for: %s\n",
 310                        size, zbackend->name);
 311                 return;
 312         }
 313
 314         ctx = crypto_alloc_comp(zbackend->name, 0, 0);
 315         if (IS_ERR_OR_NULL(ctx)) {
 316                 kfree(buf);
 317                 pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
 318                        PTR_ERR(ctx));
 319                 return;
 320         }
 321
 322         /* A non-NULL big_oops_buf indicates compression is available. */
 323         tfm = ctx;
 324         big_oops_buf_sz = size;
 325         big_oops_buf = buf;
 326
 327         pr_info("Using crash dump compression: %s\n", zbackend->name);
 328 }
 329
 330 static void free_buf_for_compression(void)
 331 {
 332         if (IS_ENABLED(CONFIG_PSTORE_COMPRESS) && tfm) {
 333                 crypto_free_comp(tfm);
 334                 tfm = NULL;
 335         }
 336         kfree(big_oops_buf);
 337         big_oops_buf = NULL;
 338         big_oops_buf_sz = 0;
 339 }
 340
 341 /*
 342  * Called when compression fails, since the printk buffer
 343  * would be fetched for compression calling it again when
 344  * compression fails would have moved the iterator of
 345  * printk buffer which results in fetching old contents.
 346  * Copy the recent messages from big_oops_buf to psinfo->buf
 347  */
 348 static size_t copy_kmsg_to_buffer(int hsize, size_t len)
 349 {
 350         size_t total_len;
 351         size_t diff;
 352
 353         total_len = hsize + len;
 354
 355         if (total_len > psinfo->bufsize) {
 356                 diff = total_len - psinfo->bufsize + hsize;
 357                 memcpy(psinfo->buf, big_oops_buf, hsize);
 358                 memcpy(psinfo->buf + hsize, big_oops_buf + diff,
 359                                         psinfo->bufsize - hsize);
 360                 total_len = psinfo->bufsize;
 361         } else
 362                 memcpy(psinfo->buf, big_oops_buf, total_len);
 363
 364         return total_len;
 365 }
 366
 367 void pstore_record_init(struct pstore_record *record,
 368                         struct pstore_info *psinfo)
 369 {
 370         memset(record, 0, sizeof(*record));
 371
 372         record->psi = psinfo;
 373
 374         /* Report zeroed timestamp if called before timekeeping has resumed. */
 375         record->time = ns_to_timespec64(ktime_get_real_fast_ns());
 376 }
 377
 378 /*
 379  * callback from kmsg_dump. Save as much as we can (up to kmsg_bytes) from the
 380  * end of the buffer.
 381  */
 382 static void pstore_dump(struct kmsg_dumper *dumper,
 383                         enum kmsg_dump_reason reason)
 384 {
 385         unsigned long   total = 0;
 386         const char      *why;
 387         unsigned int    part = 1;
 388         int             ret;
 389
 390         why = kmsg_dump_reason_str(reason);
 391
 392         if (down_trylock(&psinfo->buf_lock)) {
 393                 /* Failed to acquire lock: give up if we cannot wait. */
 394                 if (pstore_cannot_wait(reason)) {
 395                         pr_err("dump skipped in %s path: may corrupt error record\n",
 396                                 in_nmi() ? "NMI" : why);
 397                         return;
 398                 }
 399                 if (down_interruptible(&psinfo->buf_lock)) {
 400                         pr_err("could not grab semaphore?!\n");
 401                         return;
 402                 }
 403         }
 404
 405         oopscount++;
 406         while (total < kmsg_bytes) {
 407                 char *dst;
 408                 size_t dst_size;
 409                 int header_size;
 410                 int zipped_len = -1;
 411                 size_t dump_size;
 412                 struct pstore_record record;
 413
 414                 pstore_record_init(&record, psinfo);
 415                 record.type = PSTORE_TYPE_DMESG;
 416                 record.count = oopscount;
 417                 record.reason = reason;
 418                 record.part = part;
 419                 record.buf = psinfo->buf;
 420
 421                 if (big_oops_buf) {
 422                         dst = big_oops_buf;
 423                         dst_size = big_oops_buf_sz;
 424                 } else {
 425                         dst = psinfo->buf;
 426                         dst_size = psinfo->bufsize;
 427                 }
 428
 429                 /* Write dump header. */
 430                 header_size = snprintf(dst, dst_size, "%s#%d Part%u\n", why,
 431                                  oopscount, part);
 432                 dst_size -= header_size;
 433
 434                 /* Write dump contents. */
 435                 if (!kmsg_dump_get_buffer(dumper, true, dst + header_size,
 436                                           dst_size, &dump_size))
 437                         break;
 438
 439                 if (big_oops_buf) {
 440                         zipped_len = pstore_compress(dst, psinfo->buf,
 441                                                 header_size + dump_size,
 442                                                 psinfo->bufsize);
 443
 444                         if (zipped_len > 0) {
 445                                 record.compressed = true;
 446                                 record.size = zipped_len;
 447                         } else {
 448                                 record.size = copy_kmsg_to_buffer(header_size,
 449                                                                   dump_size);
 450                         }
 451                 } else {
 452                         record.size = header_size + dump_size;
 453                 }
 454
 455                 ret = psinfo->write(&record);
 456                 if (ret == 0 && reason == KMSG_DUMP_OOPS) {
 457                         pstore_new_entry = 1;
 458                         pstore_timer_kick();
 459                 }
 460
 461                 total += record.size;
 462                 part++;
 463         }
 464
 465         up(&psinfo->buf_lock);
 466 }
 467
 468 static struct kmsg_dumper pstore_dumper = {
 469         .dump = pstore_dump,
 470 };
 471
 472 /*
 473  * Register with kmsg_dump to save last part of console log on panic.
 474  */
 475 static void pstore_register_kmsg(void)
 476 {
 477         kmsg_dump_register(&pstore_dumper);
 478 }
 479
 480 static void pstore_unregister_kmsg(void)
 481 {
 482         kmsg_dump_unregister(&pstore_dumper);
 483 }
 484
 485 #ifdef CONFIG_PSTORE_CONSOLE
 486 static void pstore_console_write(struct console *con, const char *s, unsigned c)
 487 {
 488         struct pstore_record record;
 489
 490         if (!c)
 491                 return;
 492
 493         pstore_record_init(&record, psinfo);
 494         record.type = PSTORE_TYPE_CONSOLE;
 495
 496         record.buf = (char *)s;
 497         record.size = c;
 498         psinfo->write(&record);
 499 }
 500
 501 static struct console pstore_console = {
 502         .write  = pstore_console_write,
 503         .index  = -1,
 504 };
 505
 506 static void pstore_register_console(void)
 507 {
 508         /* Show which backend is going to get console writes. */
 509         strscpy(pstore_console.name, psinfo->name,
 510                 sizeof(pstore_console.name));
 511         /*
 512          * Always initialize flags here since prior unregister_console()
 513          * calls may have changed settings (specifically CON_ENABLED).
 514          */
 515         pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
 516         register_console(&pstore_console);
 517 }
 518
 519 static void pstore_unregister_console(void)
 520 {
 521         unregister_console(&pstore_console);
 522 }
 523 #else
 524 static void pstore_register_console(void) {}
 525 static void pstore_unregister_console(void) {}
 526 #endif
 527
 528 static int pstore_write_user_compat(struct pstore_record *record,
 529                                     const char __user *buf)
 530 {
 531         int ret = 0;
 532
 533         if (record->buf)
 534                 return -EINVAL;
 535
 536         record->buf = memdup_user(buf, record->size);
 537         if (IS_ERR(record->buf)) {
 538                 ret = PTR_ERR(record->buf);
 539                 goto out;
 540         }
 541
 542         ret = record->psi->write(record);
 543
 544         kfree(record->buf);
 545 out:
 546         record->buf = NULL;
 547
 548         return unlikely(ret < 0) ? ret : record->size;
 549 }
 550
 551 /*
 552  * platform specific persistent storage driver registers with
 553  * us here. If pstore is already mounted, call the platform
 554  * read function right away to populate the file system. If not
 555  * then the pstore mount code will call us later to fill out
 556  * the file system.
 557  */
 558 int pstore_register(struct pstore_info *psi)
 559 {
 560         if (backend && strcmp(backend, psi->name)) {
 561                 pr_warn("ignoring unexpected backend '%s'\n", psi->name);
 562                 return -EPERM;
 563         }
 564
 565         /* Sanity check flags. */
 566         if (!psi->flags) {
 567                 pr_warn("backend '%s' must support at least one frontend\n",
 568                         psi->name);
 569                 return -EINVAL;
 570         }
 571
 572         /* Check for required functions. */
 573         if (!psi->read || !psi->write) {
 574                 pr_warn("backend '%s' must implement read() and write()\n",
 575                         psi->name);
 576                 return -EINVAL;
 577         }
 578
 579         mutex_lock(&psinfo_lock);
 580         if (psinfo) {
 581                 pr_warn("backend '%s' already loaded: ignoring '%s'\n",
 582                         psinfo->name, psi->name);
 583                 mutex_unlock(&psinfo_lock);
 584                 return -EBUSY;
 585         }
 586
 587         if (!psi->write_user)
 588                 psi->write_user = pstore_write_user_compat;
 589         psinfo = psi;
 590         mutex_init(&psinfo->read_mutex);
 591         sema_init(&psinfo->buf_lock, 1);
 592
 593         if (psi->flags & PSTORE_FLAGS_DMESG)
 594                 allocate_buf_for_compression();
 595
 596         pstore_get_records(0);
 597
 598         if (psi->flags & PSTORE_FLAGS_DMESG) {
 599                 pstore_dumper.max_reason = psinfo->max_reason;
 600                 pstore_register_kmsg();
 601         }
 602         if (psi->flags & PSTORE_FLAGS_CONSOLE)
 603                 pstore_register_console();
 604         if (psi->flags & PSTORE_FLAGS_FTRACE)
 605                 pstore_register_ftrace();
 606         if (psi->flags & PSTORE_FLAGS_PMSG)
 607                 pstore_register_pmsg();
 608
 609         /* Start watching for new records, if desired. */
 610         pstore_timer_kick();
 611
 612         /*
 613          * Update the module parameter backend, so it is visible
 614          * through /sys/module/pstore/parameters/backend
 615          */
 616         backend = kstrdup(psi->name, GFP_KERNEL);
 617
 618         pr_info("Registered %s as persistent store backend\n", psi->name);
 619
 620         mutex_unlock(&psinfo_lock);
 621         return 0;
 622 }
 623 EXPORT_SYMBOL_GPL(pstore_register);
 624
 625 void pstore_unregister(struct pstore_info *psi)
 626 {
 627         /* It's okay to unregister nothing. */
 628         if (!psi)
 629                 return;
 630
 631         mutex_lock(&psinfo_lock);
 632
 633         /* Only one backend can be registered at a time. */
 634         if (WARN_ON(psi != psinfo)) {
 635                 mutex_unlock(&psinfo_lock);
 636                 return;
 637         }
 638
 639         /* Unregister all callbacks. */
 640         if (psi->flags & PSTORE_FLAGS_PMSG)
 641                 pstore_unregister_pmsg();
 642         if (psi->flags & PSTORE_FLAGS_FTRACE)
 643                 pstore_unregister_ftrace();
 644         if (psi->flags & PSTORE_FLAGS_CONSOLE)
 645                 pstore_unregister_console();
 646         if (psi->flags & PSTORE_FLAGS_DMESG)
 647                 pstore_unregister_kmsg();
 648
 649         /* Stop timer and make sure all work has finished. */
 650         del_timer_sync(&pstore_timer);
 651         flush_work(&pstore_work);
 652
 653         /* Remove all backend records from filesystem tree. */
 654         pstore_put_backend_records(psi);
 655
 656         free_buf_for_compression();
 657
 658         psinfo = NULL;
 659         kfree(backend);
 660         backend = NULL;
 661         mutex_unlock(&psinfo_lock);
 662 }
 663 EXPORT_SYMBOL_GPL(pstore_unregister);
 664
 665 static void decompress_record(struct pstore_record *record)
 666 {
 667         int ret;
 668         int unzipped_len;
 669         char *unzipped, *workspace;
 670
 671         if (!record->compressed)
 672                 return;
 673
 674         /* Only PSTORE_TYPE_DMESG support compression. */
 675         if (record->type != PSTORE_TYPE_DMESG) {
 676                 pr_warn("ignored compressed record type %d\n", record->type);
 677                 return;
 678         }
 679
 680         /* Missing compression buffer means compression was not initialized. */
 681         if (!big_oops_buf) {
 682                 pr_warn("no decompression method initialized!\n");
 683                 return;
 684         }
 685
 686         /* Allocate enough space to hold max decompression and ECC. */
 687         unzipped_len = big_oops_buf_sz;
 688         workspace = kmalloc(unzipped_len + record->ecc_notice_size,
 689                             GFP_KERNEL);
 690         if (!workspace)
 691                 return;
 692
 693         /* After decompression "unzipped_len" is almost certainly smaller. */
 694         ret = crypto_comp_decompress(tfm, record->buf, record->size,
 695                                           workspace, &unzipped_len);
 696         if (ret) {
 697                 pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
 698                 kfree(workspace);
 699                 return;
 700         }
 701
 702         /* Append ECC notice to decompressed buffer. */
 703         memcpy(workspace + unzipped_len, record->buf + record->size,
 704                record->ecc_notice_size);
 705
 706         /* Copy decompressed contents into an minimum-sized allocation. */
 707         unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
 708                            GFP_KERNEL);
 709         kfree(workspace);
 710         if (!unzipped)
 711                 return;
 712
 713         /* Swap out compressed contents with decompressed contents. */
 714         kfree(record->buf);
 715         record->buf = unzipped;
 716         record->size = unzipped_len;
 717         record->compressed = false;
 718 }
 719
 720 /*
 721  * Read all the records from one persistent store backend. Create
 722  * files in our filesystem.  Don't warn about -EEXIST errors
 723  * when we are re-scanning the backing store looking to add new
 724  * error records.
 725  */
 726 void pstore_get_backend_records(struct pstore_info *psi,
 727                                 struct dentry *root, int quiet)
 728 {
 729         int failed = 0;
 730         unsigned int stop_loop = 65536;
 731
 732         if (!psi || !root)
 733                 return;
 734
 735         mutex_lock(&psi->read_mutex);
 736         if (psi->open && psi->open(psi))
 737                 goto out;
 738
 739         /*
 740          * Backend callback read() allocates record.buf. decompress_record()
 741          * may reallocate record.buf. On success, pstore_mkfile() will keep
 742          * the record.buf, so free it only on failure.
 743          */
 744         for (; stop_loop; stop_loop--) {
 745                 struct pstore_record *record;
 746                 int rc;
 747
 748                 record = kzalloc(sizeof(*record), GFP_KERNEL);
 749                 if (!record) {
 750                         pr_err("out of memory creating record\n");
 751                         break;
 752                 }
 753                 pstore_record_init(record, psi);
 754
 755                 record->size = psi->read(record);
 756
 757                 /* No more records left in backend? */
 758                 if (record->size <= 0) {
 759                         kfree(record);
 760                         break;
 761                 }
 762
 763                 decompress_record(record);
 764                 rc = pstore_mkfile(root, record);
 765                 if (rc) {
 766                         /* pstore_mkfile() did not take record, so free it. */
 767                         kfree(record->buf);
 768                         kfree(record);
 769                         if (rc != -EEXIST || !quiet)
 770                                 failed++;
 771                 }
 772         }
 773         if (psi->close)
 774                 psi->close(psi);
 775 out:
 776         mutex_unlock(&psi->read_mutex);
 777
 778         if (failed)
 779                 pr_warn("failed to create %d record(s) from '%s'\n",
 780                         failed, psi->name);
 781         if (!stop_loop)
 782                 pr_err("looping? Too many records seen from '%s'\n",
 783                         psi->name);
 784 }
 785
 786 static void pstore_dowork(struct work_struct *work)
 787 {
 788         pstore_get_records(1);
 789 }
 790
 791 static void pstore_timefunc(struct timer_list *unused)
 792 {
 793         if (pstore_new_entry) {
 794                 pstore_new_entry = 0;
 795                 schedule_work(&pstore_work);
 796         }
 797
 798         pstore_timer_kick();
 799 }
 800
 801 static void __init pstore_choose_compression(void)
 802 {
 803         const struct pstore_zbackend *step;
 804
 805         if (!compress)
 806                 return;
 807
 808         for (step = zbackends; step->name; step++) {
 809                 if (!strcmp(compress, step->name)) {
 810                         zbackend = step;
 811                         return;
 812                 }
 813         }
 814 }
 815
 816 static int __init pstore_init(void)
 817 {
 818         int ret;
 819
 820         pstore_choose_compression();
 821
 822         /*
 823          * Check if any pstore backends registered earlier but did not
 824          * initialize compression because crypto was not ready. If so,
 825          * initialize compression now.
 826          */
 827         allocate_buf_for_compression();
 828
 829         ret = pstore_init_fs();
 830         if (ret)
 831                 free_buf_for_compression();
 832
 833         return ret;
 834 }
 835 late_initcall(pstore_init);
 836
 837 static void __exit pstore_exit(void)
 838 {
 839         pstore_exit_fs();
 840 }
 841 module_exit(pstore_exit)
 842
 843 MODULE_AUTHOR("Tony Luck <tony.luck@intel.com>");
 844 MODULE_LICENSE("GPL");