fs/btrfs/scrub.c

   1 /*
   2  * Copyright (C) 2011 STRATO.  All rights reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public
   6  * License v2 as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public
  14  * License along with this program; if not, write to the
  15  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  16  * Boston, MA 021110-1307, USA.
  17  */
  18
  19 #include <linux/blkdev.h>
  20 #include <linux/ratelimit.h>
  21 #include "ctree.h"
  22 #include "volumes.h"
  23 #include "disk-io.h"
  24 #include "ordered-data.h"
  25 #include "transaction.h"
  26 #include "backref.h"
  27 #include "extent_io.h"
  28 #include "check-integrity.h"
  29 #include "rcu-string.h"
  30
  31 /*
  32  * This is only the first step towards a full-features scrub. It reads all
  33  * extent and super block and verifies the checksums. In case a bad checksum
  34  * is found or the extent cannot be read, good data will be written back if
  35  * any can be found.
  36  *
  37  * Future enhancements:
  38  *  - In case an unrepairable extent is encountered, track which files are
  39  *    affected and report them
  40  *  - track and record media errors, throw out bad devices
  41  *  - add a mode to also read unallocated space
  42  */
  43
  44 struct scrub_block;
  45 struct scrub_ctx;
  46
  47 #define SCRUB_PAGES_PER_BIO     16      /* 64k per bio */
  48 #define SCRUB_BIOS_PER_CTX      16      /* 1 MB per device in flight */
  49 #define SCRUB_MAX_PAGES_PER_BLOCK       16      /* 64k per node/leaf/sector */
  50
  51 struct scrub_page {
  52         struct scrub_block      *sblock;
  53         struct page             *page;
  54         struct btrfs_device     *dev;
  55         u64                     flags;  /* extent flags */
  56         u64                     generation;
  57         u64                     logical;
  58         u64                     physical;
  59         struct {
  60                 unsigned int    mirror_num:8;
  61                 unsigned int    have_csum:1;
  62                 unsigned int    io_error:1;
  63         };
  64         u8                      csum[BTRFS_CSUM_SIZE];
  65 };
  66
  67 struct scrub_bio {
  68         int                     index;
  69         struct scrub_ctx        *sctx;
  70         struct btrfs_device     *dev;
  71         struct bio              *bio;
  72         int                     err;
  73         u64                     logical;
  74         u64                     physical;
  75         struct scrub_page       *pagev[SCRUB_PAGES_PER_BIO];
  76         int                     page_count;
  77         int                     next_free;
  78         struct btrfs_work       work;
  79 };
  80
  81 struct scrub_block {
  82         struct scrub_page       pagev[SCRUB_MAX_PAGES_PER_BLOCK];
  83         int                     page_count;
  84         atomic_t                outstanding_pages;
  85         atomic_t                ref_count; /* free mem on transition to zero */
  86         struct scrub_ctx        *sctx;
  87         struct {
  88                 unsigned int    header_error:1;
  89                 unsigned int    checksum_error:1;
  90                 unsigned int    no_io_error_seen:1;
  91                 unsigned int    generation_error:1; /* also sets header_error */
  92         };
  93 };
  94
  95 struct scrub_ctx {
  96         struct scrub_bio        *bios[SCRUB_BIOS_PER_CTX];
  97         struct btrfs_root       *dev_root;
  98         int                     first_free;
  99         int                     curr;
 100         atomic_t                in_flight;
 101         atomic_t                fixup_cnt;
 102         spinlock_t              list_lock;
 103         wait_queue_head_t       list_wait;
 104         u16                     csum_size;
 105         struct list_head        csum_list;
 106         atomic_t                cancel_req;
 107         int                     readonly;
 108         int                     pages_per_bio; /* <= SCRUB_PAGES_PER_BIO */
 109         u32                     sectorsize;
 110         u32                     nodesize;
 111         u32                     leafsize;
 112         /*
 113          * statistics
 114          */
 115         struct btrfs_scrub_progress stat;
 116         spinlock_t              stat_lock;
 117 };
 118
 119 struct scrub_fixup_nodatasum {
 120         struct scrub_ctx        *sctx;
 121         struct btrfs_device     *dev;
 122         u64                     logical;
 123         struct btrfs_root       *root;
 124         struct btrfs_work       work;
 125         int                     mirror_num;
 126 };
 127
 128 struct scrub_warning {
 129         struct btrfs_path       *path;
 130         u64                     extent_item_size;
 131         char                    *scratch_buf;
 132         char                    *msg_buf;
 133         const char              *errstr;
 134         sector_t                sector;
 135         u64                     logical;
 136         struct btrfs_device     *dev;
 137         int                     msg_bufsize;
 138         int                     scratch_bufsize;
 139 };
 140
 141
 142 static int scrub_handle_errored_block(struct scrub_block *sblock_to_check);
 143 static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
 144                                      struct btrfs_mapping_tree *map_tree,
 145                                      u64 length, u64 logical,
 146                                      struct scrub_block *sblock);
 147 static int scrub_recheck_block(struct btrfs_fs_info *fs_info,
 148                                struct scrub_block *sblock, int is_metadata,
 149                                int have_csum, u8 *csum, u64 generation,
 150                                u16 csum_size);
 151 static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
 152                                          struct scrub_block *sblock,
 153                                          int is_metadata, int have_csum,
 154                                          const u8 *csum, u64 generation,
 155                                          u16 csum_size);
 156 static void scrub_complete_bio_end_io(struct bio *bio, int err);
 157 static int scrub_repair_block_from_good_copy(struct scrub_block *sblock_bad,
 158                                              struct scrub_block *sblock_good,
 159                                              int force_write);
 160 static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
 161                                             struct scrub_block *sblock_good,
 162                                             int page_num, int force_write);
 163 static int scrub_checksum_data(struct scrub_block *sblock);
 164 static int scrub_checksum_tree_block(struct scrub_block *sblock);
 165 static int scrub_checksum_super(struct scrub_block *sblock);
 166 static void scrub_block_get(struct scrub_block *sblock);
 167 static void scrub_block_put(struct scrub_block *sblock);
 168 static int scrub_add_page_to_bio(struct scrub_ctx *sctx,
 169                                  struct scrub_page *spage);
 170 static int scrub_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
 171                        u64 physical, struct btrfs_device *dev, u64 flags,
 172                        u64 gen, int mirror_num, u8 *csum, int force);
 173 static void scrub_bio_end_io(struct bio *bio, int err);
 174 static void scrub_bio_end_io_worker(struct btrfs_work *work);
 175 static void scrub_block_complete(struct scrub_block *sblock);
 176
 177
 178 static void scrub_free_csums(struct scrub_ctx *sctx)
 179 {
 180         while (!list_empty(&sctx->csum_list)) {
 181                 struct btrfs_ordered_sum *sum;
 182                 sum = list_first_entry(&sctx->csum_list,
 183                                        struct btrfs_ordered_sum, list);
 184                 list_del(&sum->list);
 185                 kfree(sum);
 186         }
 187 }
 188
 189 static noinline_for_stack void scrub_free_ctx(struct scrub_ctx *sctx)
 190 {
 191         int i;
 192
 193         if (!sctx)
 194                 return;
 195
 196         /* this can happen when scrub is cancelled */
 197         if (sctx->curr != -1) {
 198                 struct scrub_bio *sbio = sctx->bios[sctx->curr];
 199
 200                 for (i = 0; i < sbio->page_count; i++) {
 201                         BUG_ON(!sbio->pagev[i]);
 202                         BUG_ON(!sbio->pagev[i]->page);
 203                         scrub_block_put(sbio->pagev[i]->sblock);
 204                 }
 205                 bio_put(sbio->bio);
 206         }
 207
 208         for (i = 0; i < SCRUB_BIOS_PER_CTX; ++i) {
 209                 struct scrub_bio *sbio = sctx->bios[i];
 210
 211                 if (!sbio)
 212                         break;
 213                 kfree(sbio);
 214         }
 215
 216         scrub_free_csums(sctx);
 217         kfree(sctx);
 218 }
 219
 220 static noinline_for_stack
 221 struct scrub_ctx *scrub_setup_ctx(struct btrfs_device *dev)
 222 {
 223         struct scrub_ctx *sctx;
 224         int             i;
 225         struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
 226         int pages_per_bio;
 227
 228         pages_per_bio = min_t(int, SCRUB_PAGES_PER_BIO,
 229                               bio_get_nr_vecs(dev->bdev));
 230         sctx = kzalloc(sizeof(*sctx), GFP_NOFS);
 231         if (!sctx)
 232                 goto nomem;
 233         sctx->pages_per_bio = pages_per_bio;
 234         sctx->curr = -1;
 235         sctx->dev_root = dev->dev_root;
 236         for (i = 0; i < SCRUB_BIOS_PER_CTX; ++i) {
 237                 struct scrub_bio *sbio;
 238
 239                 sbio = kzalloc(sizeof(*sbio), GFP_NOFS);
 240                 if (!sbio)
 241                         goto nomem;
 242                 sctx->bios[i] = sbio;
 243
 244                 sbio->index = i;
 245                 sbio->sctx = sctx;
 246                 sbio->page_count = 0;
 247                 sbio->work.func = scrub_bio_end_io_worker;
 248
 249                 if (i != SCRUB_BIOS_PER_CTX - 1)
 250                         sctx->bios[i]->next_free = i + 1;
 251                 else
 252                         sctx->bios[i]->next_free = -1;
 253         }
 254         sctx->first_free = 0;
 255         sctx->nodesize = dev->dev_root->nodesize;
 256         sctx->leafsize = dev->dev_root->leafsize;
 257         sctx->sectorsize = dev->dev_root->sectorsize;
 258         atomic_set(&sctx->in_flight, 0);
 259         atomic_set(&sctx->fixup_cnt, 0);
 260         atomic_set(&sctx->cancel_req, 0);
 261         sctx->csum_size = btrfs_super_csum_size(fs_info->super_copy);
 262         INIT_LIST_HEAD(&sctx->csum_list);
 263
 264         spin_lock_init(&sctx->list_lock);
 265         spin_lock_init(&sctx->stat_lock);
 266         init_waitqueue_head(&sctx->list_wait);
 267         return sctx;
 268
 269 nomem:
 270         scrub_free_ctx(sctx);
 271         return ERR_PTR(-ENOMEM);
 272 }
 273
 274 static int scrub_print_warning_inode(u64 inum, u64 offset, u64 root, void *ctx)
 275 {
 276         u64 isize;
 277         u32 nlink;
 278         int ret;
 279         int i;
 280         struct extent_buffer *eb;
 281         struct btrfs_inode_item *inode_item;
 282         struct scrub_warning *swarn = ctx;
 283         struct btrfs_fs_info *fs_info = swarn->dev->dev_root->fs_info;
 284         struct inode_fs_paths *ipath = NULL;
 285         struct btrfs_root *local_root;
 286         struct btrfs_key root_key;
 287
 288         root_key.objectid = root;
 289         root_key.type = BTRFS_ROOT_ITEM_KEY;
 290         root_key.offset = (u64)-1;
 291         local_root = btrfs_read_fs_root_no_name(fs_info, &root_key);
 292         if (IS_ERR(local_root)) {
 293                 ret = PTR_ERR(local_root);
 294                 goto err;
 295         }
 296
 297         ret = inode_item_info(inum, 0, local_root, swarn->path);
 298         if (ret) {
 299                 btrfs_release_path(swarn->path);
 300                 goto err;
 301         }
 302
 303         eb = swarn->path->nodes[0];
 304         inode_item = btrfs_item_ptr(eb, swarn->path->slots[0],
 305                                         struct btrfs_inode_item);
 306         isize = btrfs_inode_size(eb, inode_item);
 307         nlink = btrfs_inode_nlink(eb, inode_item);
 308         btrfs_release_path(swarn->path);
 309
 310         ipath = init_ipath(4096, local_root, swarn->path);
 311         if (IS_ERR(ipath)) {
 312                 ret = PTR_ERR(ipath);
 313                 ipath = NULL;
 314                 goto err;
 315         }
 316         ret = paths_from_inode(inum, ipath);
 317
 318         if (ret < 0)
 319                 goto err;
 320
 321         /*
 322          * we deliberately ignore the bit ipath might have been too small to
 323          * hold all of the paths here
 324          */
 325         for (i = 0; i < ipath->fspath->elem_cnt; ++i)
 326                 printk_in_rcu(KERN_WARNING "btrfs: %s at logical %llu on dev "
 327                         "%s, sector %llu, root %llu, inode %llu, offset %llu, "
 328                         "length %llu, links %u (path: %s)\n", swarn->errstr,
 329                         swarn->logical, rcu_str_deref(swarn->dev->name),
 330                         (unsigned long long)swarn->sector, root, inum, offset,
 331                         min(isize - offset, (u64)PAGE_SIZE), nlink,
 332                         (char *)(unsigned long)ipath->fspath->val[i]);
 333
 334         free_ipath(ipath);
 335         return 0;
 336
 337 err:
 338         printk_in_rcu(KERN_WARNING "btrfs: %s at logical %llu on dev "
 339                 "%s, sector %llu, root %llu, inode %llu, offset %llu: path "
 340                 "resolving failed with ret=%d\n", swarn->errstr,
 341                 swarn->logical, rcu_str_deref(swarn->dev->name),
 342                 (unsigned long long)swarn->sector, root, inum, offset, ret);
 343
 344         free_ipath(ipath);
 345         return 0;
 346 }
 347
 348 static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
 349 {
 350         struct btrfs_device *dev;
 351         struct btrfs_fs_info *fs_info;
 352         struct btrfs_path *path;
 353         struct btrfs_key found_key;
 354         struct extent_buffer *eb;
 355         struct btrfs_extent_item *ei;
 356         struct scrub_warning swarn;
 357         unsigned long ptr = 0;
 358         u64 extent_item_pos;
 359         u64 flags = 0;
 360         u64 ref_root;
 361         u32 item_size;
 362         u8 ref_level;
 363         const int bufsize = 4096;
 364         int ret;
 365
 366         WARN_ON(sblock->page_count < 1);
 367         dev = sblock->pagev[0].dev;
 368         fs_info = sblock->sctx->dev_root->fs_info;
 369
 370         path = btrfs_alloc_path();
 371
 372         swarn.scratch_buf = kmalloc(bufsize, GFP_NOFS);
 373         swarn.msg_buf = kmalloc(bufsize, GFP_NOFS);
 374         swarn.sector = (sblock->pagev[0].physical) >> 9;
 375         swarn.logical = sblock->pagev[0].logical;
 376         swarn.errstr = errstr;
 377         swarn.dev = NULL;
 378         swarn.msg_bufsize = bufsize;
 379         swarn.scratch_bufsize = bufsize;
 380
 381         if (!path || !swarn.scratch_buf || !swarn.msg_buf)
 382                 goto out;
 383
 384         ret = extent_from_logical(fs_info, swarn.logical, path, &found_key,
 385                                   &flags);
 386         if (ret < 0)
 387                 goto out;
 388
 389         extent_item_pos = swarn.logical - found_key.objectid;
 390         swarn.extent_item_size = found_key.offset;
 391
 392         eb = path->nodes[0];
 393         ei = btrfs_item_ptr(eb, path->slots[0], struct btrfs_extent_item);
 394         item_size = btrfs_item_size_nr(eb, path->slots[0]);
 395         btrfs_release_path(path);
 396
 397         if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 398                 do {
 399                         ret = tree_backref_for_extent(&ptr, eb, ei, item_size,
 400                                                         &ref_root, &ref_level);
 401                         printk_in_rcu(KERN_WARNING
 402                                 "btrfs: %s at logical %llu on dev %s, "
 403                                 "sector %llu: metadata %s (level %d) in tree "
 404                                 "%llu\n", errstr, swarn.logical,
 405                                 rcu_str_deref(dev->name),
 406                                 (unsigned long long)swarn.sector,
 407                                 ref_level ? "node" : "leaf",
 408                                 ret < 0 ? -1 : ref_level,
 409                                 ret < 0 ? -1 : ref_root);
 410                 } while (ret != 1);
 411         } else {
 412                 swarn.path = path;
 413                 swarn.dev = dev;
 414                 iterate_extent_inodes(fs_info, found_key.objectid,
 415                                         extent_item_pos, 1,
 416                                         scrub_print_warning_inode, &swarn);
 417         }
 418
 419 out:
 420         btrfs_free_path(path);
 421         kfree(swarn.scratch_buf);
 422         kfree(swarn.msg_buf);
 423 }
 424
 425 static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *ctx)
 426 {
 427         struct page *page = NULL;
 428         unsigned long index;
 429         struct scrub_fixup_nodatasum *fixup = ctx;
 430         int ret;
 431         int corrected = 0;
 432         struct btrfs_key key;
 433         struct inode *inode = NULL;
 434         u64 end = offset + PAGE_SIZE - 1;
 435         struct btrfs_root *local_root;
 436
 437         key.objectid = root;
 438         key.type = BTRFS_ROOT_ITEM_KEY;
 439         key.offset = (u64)-1;
 440         local_root = btrfs_read_fs_root_no_name(fixup->root->fs_info, &key);
 441         if (IS_ERR(local_root))
 442                 return PTR_ERR(local_root);
 443
 444         key.type = BTRFS_INODE_ITEM_KEY;
 445         key.objectid = inum;
 446         key.offset = 0;
 447         inode = btrfs_iget(fixup->root->fs_info->sb, &key, local_root, NULL);
 448         if (IS_ERR(inode))
 449                 return PTR_ERR(inode);
 450
 451         index = offset >> PAGE_CACHE_SHIFT;
 452
 453         page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
 454         if (!page) {
 455                 ret = -ENOMEM;
 456                 goto out;
 457         }
 458
 459         if (PageUptodate(page)) {
 460                 struct btrfs_mapping_tree *map_tree;
 461                 if (PageDirty(page)) {
 462                         /*
 463                          * we need to write the data to the defect sector. the
 464                          * data that was in that sector is not in memory,
 465                          * because the page was modified. we must not write the
 466                          * modified page to that sector.
 467                          *
 468                          * TODO: what could be done here: wait for the delalloc
 469                          *       runner to write out that page (might involve
 470                          *       COW) and see whether the sector is still
 471                          *       referenced afterwards.
 472                          *
 473                          * For the meantime, we'll treat this error
 474                          * incorrectable, although there is a chance that a
 475                          * later scrub will find the bad sector again and that
 476                          * there's no dirty page in memory, then.
 477                          */
 478                         ret = -EIO;
 479                         goto out;
 480                 }
 481                 map_tree = &BTRFS_I(inode)->root->fs_info->mapping_tree;
 482                 ret = repair_io_failure(map_tree, offset, PAGE_SIZE,
 483                                         fixup->logical, page,
 484                                         fixup->mirror_num);
 485                 unlock_page(page);
 486                 corrected = !ret;
 487         } else {
 488                 /*
 489                  * we need to get good data first. the general readpage path
 490                  * will call repair_io_failure for us, we just have to make
 491                  * sure we read the bad mirror.
 492                  */
 493                 ret = set_extent_bits(&BTRFS_I(inode)->io_tree, offset, end,
 494                                         EXTENT_DAMAGED, GFP_NOFS);
 495                 if (ret) {
 496                         /* set_extent_bits should give proper error */
 497                         WARN_ON(ret > 0);
 498                         if (ret > 0)
 499                                 ret = -EFAULT;
 500                         goto out;
 501                 }
 502
 503                 ret = extent_read_full_page(&BTRFS_I(inode)->io_tree, page,
 504                                                 btrfs_get_extent,
 505                                                 fixup->mirror_num);
 506                 wait_on_page_locked(page);
 507
 508                 corrected = !test_range_bit(&BTRFS_I(inode)->io_tree, offset,
 509                                                 end, EXTENT_DAMAGED, 0, NULL);
 510                 if (!corrected)
 511                         clear_extent_bits(&BTRFS_I(inode)->io_tree, offset, end,
 512                                                 EXTENT_DAMAGED, GFP_NOFS);
 513         }
 514
 515 out:
 516         if (page)
 517                 put_page(page);
 518         if (inode)
 519                 iput(inode);
 520
 521         if (ret < 0)
 522                 return ret;
 523
 524         if (ret == 0 && corrected) {
 525                 /*
 526                  * we only need to call readpage for one of the inodes belonging
 527                  * to this extent. so make iterate_extent_inodes stop
 528                  */
 529                 return 1;
 530         }
 531
 532         return -EIO;
 533 }
 534
 535 static void scrub_fixup_nodatasum(struct btrfs_work *work)
 536 {
 537         int ret;
 538         struct scrub_fixup_nodatasum *fixup;
 539         struct scrub_ctx *sctx;
 540         struct btrfs_trans_handle *trans = NULL;
 541         struct btrfs_fs_info *fs_info;
 542         struct btrfs_path *path;
 543         int uncorrectable = 0;
 544
 545         fixup = container_of(work, struct scrub_fixup_nodatasum, work);
 546         sctx = fixup->sctx;
 547         fs_info = fixup->root->fs_info;
 548
 549         path = btrfs_alloc_path();
 550         if (!path) {
 551                 spin_lock(&sctx->stat_lock);
 552                 ++sctx->stat.malloc_errors;
 553                 spin_unlock(&sctx->stat_lock);
 554                 uncorrectable = 1;
 555                 goto out;
 556         }
 557
 558         trans = btrfs_join_transaction(fixup->root);
 559         if (IS_ERR(trans)) {
 560                 uncorrectable = 1;
 561                 goto out;
 562         }
 563
 564         /*
 565          * the idea is to trigger a regular read through the standard path. we
 566          * read a page from the (failed) logical address by specifying the
 567          * corresponding copynum of the failed sector. thus, that readpage is
 568          * expected to fail.
 569          * that is the point where on-the-fly error correction will kick in
 570          * (once it's finished) and rewrite the failed sector if a good copy
 571          * can be found.
 572          */
 573         ret = iterate_inodes_from_logical(fixup->logical, fixup->root->fs_info,
 574                                                 path, scrub_fixup_readpage,
 575                                                 fixup);
 576         if (ret < 0) {
 577                 uncorrectable = 1;
 578                 goto out;
 579         }
 580         WARN_ON(ret != 1);
 581
 582         spin_lock(&sctx->stat_lock);
 583         ++sctx->stat.corrected_errors;
 584         spin_unlock(&sctx->stat_lock);
 585
 586 out:
 587         if (trans && !IS_ERR(trans))
 588                 btrfs_end_transaction(trans, fixup->root);
 589         if (uncorrectable) {
 590                 spin_lock(&sctx->stat_lock);
 591                 ++sctx->stat.uncorrectable_errors;
 592                 spin_unlock(&sctx->stat_lock);
 593
 594                 printk_ratelimited_in_rcu(KERN_ERR
 595                         "btrfs: unable to fixup (nodatasum) error at logical %llu on dev %s\n",
 596                         (unsigned long long)fixup->logical,
 597                         rcu_str_deref(fixup->dev->name));
 598         }
 599
 600         btrfs_free_path(path);
 601         kfree(fixup);
 602
 603         /* see caller why we're pretending to be paused in the scrub counters */
 604         mutex_lock(&fs_info->scrub_lock);
 605         atomic_dec(&fs_info->scrubs_running);
 606         atomic_dec(&fs_info->scrubs_paused);
 607         mutex_unlock(&fs_info->scrub_lock);
 608         atomic_dec(&sctx->fixup_cnt);
 609         wake_up(&fs_info->scrub_pause_wait);
 610         wake_up(&sctx->list_wait);
 611 }
 612
 613 /*
 614  * scrub_handle_errored_block gets called when either verification of the
 615  * pages failed or the bio failed to read, e.g. with EIO. In the latter
 616  * case, this function handles all pages in the bio, even though only one
 617  * may be bad.
 618  * The goal of this function is to repair the errored block by using the
 619  * contents of one of the mirrors.
 620  */
 621 static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
 622 {
 623         struct scrub_ctx *sctx = sblock_to_check->sctx;
 624         struct btrfs_device *dev;
 625         struct btrfs_fs_info *fs_info;
 626         u64 length;
 627         u64 logical;
 628         u64 generation;
 629         unsigned int failed_mirror_index;
 630         unsigned int is_metadata;
 631         unsigned int have_csum;
 632         u8 *csum;
 633         struct scrub_block *sblocks_for_recheck; /* holds one for each mirror */
 634         struct scrub_block *sblock_bad;
 635         int ret;
 636         int mirror_index;
 637         int page_num;
 638         int success;
 639         static DEFINE_RATELIMIT_STATE(_rs, DEFAULT_RATELIMIT_INTERVAL,
 640                                       DEFAULT_RATELIMIT_BURST);
 641
 642         BUG_ON(sblock_to_check->page_count < 1);
 643         fs_info = sctx->dev_root->fs_info;
 644         length = sblock_to_check->page_count * PAGE_SIZE;
 645         logical = sblock_to_check->pagev[0].logical;
 646         generation = sblock_to_check->pagev[0].generation;
 647         BUG_ON(sblock_to_check->pagev[0].mirror_num < 1);
 648         failed_mirror_index = sblock_to_check->pagev[0].mirror_num - 1;
 649         is_metadata = !(sblock_to_check->pagev[0].flags &
 650                         BTRFS_EXTENT_FLAG_DATA);
 651         have_csum = sblock_to_check->pagev[0].have_csum;
 652         csum = sblock_to_check->pagev[0].csum;
 653         dev = sblock_to_check->pagev[0].dev;
 654
 655         /*
 656          * read all mirrors one after the other. This includes to
 657          * re-read the extent or metadata block that failed (that was
 658          * the cause that this fixup code is called) another time,
 659          * page by page this time in order to know which pages
 660          * caused I/O errors and which ones are good (for all mirrors).
 661          * It is the goal to handle the situation when more than one
 662          * mirror contains I/O errors, but the errors do not
 663          * overlap, i.e. the data can be repaired by selecting the
 664          * pages from those mirrors without I/O error on the
 665          * particular pages. One example (with blocks >= 2 * PAGE_SIZE)
 666          * would be that mirror #1 has an I/O error on the first page,
 667          * the second page is good, and mirror #2 has an I/O error on
 668          * the second page, but the first page is good.
 669          * Then the first page of the first mirror can be repaired by
 670          * taking the first page of the second mirror, and the
 671          * second page of the second mirror can be repaired by
 672          * copying the contents of the 2nd page of the 1st mirror.
 673          * One more note: if the pages of one mirror contain I/O
 674          * errors, the checksum cannot be verified. In order to get
 675          * the best data for repairing, the first attempt is to find
 676          * a mirror without I/O errors and with a validated checksum.
 677          * Only if this is not possible, the pages are picked from
 678          * mirrors with I/O errors without considering the checksum.
 679          * If the latter is the case, at the end, the checksum of the
 680          * repaired area is verified in order to correctly maintain
 681          * the statistics.
 682          */
 683
 684         sblocks_for_recheck = kzalloc(BTRFS_MAX_MIRRORS *
 685                                      sizeof(*sblocks_for_recheck),
 686                                      GFP_NOFS);
 687         if (!sblocks_for_recheck) {
 688                 spin_lock(&sctx->stat_lock);
 689                 sctx->stat.malloc_errors++;
 690                 sctx->stat.read_errors++;
 691                 sctx->stat.uncorrectable_errors++;
 692                 spin_unlock(&sctx->stat_lock);
 693                 btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 694                 goto out;
 695         }
 696
 697         /* setup the context, map the logical blocks and alloc the pages */
 698         ret = scrub_setup_recheck_block(sctx, &fs_info->mapping_tree, length,
 699                                         logical, sblocks_for_recheck);
 700         if (ret) {
 701                 spin_lock(&sctx->stat_lock);
 702                 sctx->stat.read_errors++;
 703                 sctx->stat.uncorrectable_errors++;
 704                 spin_unlock(&sctx->stat_lock);
 705                 btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 706                 goto out;
 707         }
 708         BUG_ON(failed_mirror_index >= BTRFS_MAX_MIRRORS);
 709         sblock_bad = sblocks_for_recheck + failed_mirror_index;
 710
 711         /* build and submit the bios for the failed mirror, check checksums */
 712         ret = scrub_recheck_block(fs_info, sblock_bad, is_metadata, have_csum,
 713                                   csum, generation, sctx->csum_size);
 714         if (ret) {
 715                 spin_lock(&sctx->stat_lock);
 716                 sctx->stat.read_errors++;
 717                 sctx->stat.uncorrectable_errors++;
 718                 spin_unlock(&sctx->stat_lock);
 719                 btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 720                 goto out;
 721         }
 722
 723         if (!sblock_bad->header_error && !sblock_bad->checksum_error &&
 724             sblock_bad->no_io_error_seen) {
 725                 /*
 726                  * the error disappeared after reading page by page, or
 727                  * the area was part of a huge bio and other parts of the
 728                  * bio caused I/O errors, or the block layer merged several
 729                  * read requests into one and the error is caused by a
 730                  * different bio (usually one of the two latter cases is
 731                  * the cause)
 732                  */
 733                 spin_lock(&sctx->stat_lock);
 734                 sctx->stat.unverified_errors++;
 735                 spin_unlock(&sctx->stat_lock);
 736
 737                 goto out;
 738         }
 739
 740         if (!sblock_bad->no_io_error_seen) {
 741                 spin_lock(&sctx->stat_lock);
 742                 sctx->stat.read_errors++;
 743                 spin_unlock(&sctx->stat_lock);
 744                 if (__ratelimit(&_rs))
 745                         scrub_print_warning("i/o error", sblock_to_check);
 746                 btrfs_dev_stat_inc_and_print(dev, BTRFS_DEV_STAT_READ_ERRS);
 747         } else if (sblock_bad->checksum_error) {
 748                 spin_lock(&sctx->stat_lock);
 749                 sctx->stat.csum_errors++;
 750                 spin_unlock(&sctx->stat_lock);
 751                 if (__ratelimit(&_rs))
 752                         scrub_print_warning("checksum error", sblock_to_check);
 753                 btrfs_dev_stat_inc_and_print(dev,
 754                                              BTRFS_DEV_STAT_CORRUPTION_ERRS);
 755         } else if (sblock_bad->header_error) {
 756                 spin_lock(&sctx->stat_lock);
 757                 sctx->stat.verify_errors++;
 758                 spin_unlock(&sctx->stat_lock);
 759                 if (__ratelimit(&_rs))
 760                         scrub_print_warning("checksum/header error",
 761                                             sblock_to_check);
 762                 if (sblock_bad->generation_error)
 763                         btrfs_dev_stat_inc_and_print(dev,
 764                                 BTRFS_DEV_STAT_GENERATION_ERRS);
 765                 else
 766                         btrfs_dev_stat_inc_and_print(dev,
 767                                 BTRFS_DEV_STAT_CORRUPTION_ERRS);
 768         }
 769
 770         if (sctx->readonly)
 771                 goto did_not_correct_error;
 772
 773         if (!is_metadata && !have_csum) {
 774                 struct scrub_fixup_nodatasum *fixup_nodatasum;
 775
 776                 /*
 777                  * !is_metadata and !have_csum, this means that the data
 778                  * might not be COW'ed, that it might be modified
 779                  * concurrently. The general strategy to work on the
 780                  * commit root does not help in the case when COW is not
 781                  * used.
 782                  */
 783                 fixup_nodatasum = kzalloc(sizeof(*fixup_nodatasum), GFP_NOFS);
 784                 if (!fixup_nodatasum)
 785                         goto did_not_correct_error;
 786                 fixup_nodatasum->sctx = sctx;
 787                 fixup_nodatasum->dev = dev;
 788                 fixup_nodatasum->logical = logical;
 789                 fixup_nodatasum->root = fs_info->extent_root;
 790                 fixup_nodatasum->mirror_num = failed_mirror_index + 1;
 791                 /*
 792                  * increment scrubs_running to prevent cancel requests from
 793                  * completing as long as a fixup worker is running. we must also
 794                  * increment scrubs_paused to prevent deadlocking on pause
 795                  * requests used for transactions commits (as the worker uses a
 796                  * transaction context). it is safe to regard the fixup worker
 797                  * as paused for all matters practical. effectively, we only
 798                  * avoid cancellation requests from completing.
 799                  */
 800                 mutex_lock(&fs_info->scrub_lock);
 801                 atomic_inc(&fs_info->scrubs_running);
 802                 atomic_inc(&fs_info->scrubs_paused);
 803                 mutex_unlock(&fs_info->scrub_lock);
 804                 atomic_inc(&sctx->fixup_cnt);
 805                 fixup_nodatasum->work.func = scrub_fixup_nodatasum;
 806                 btrfs_queue_worker(&fs_info->scrub_workers,
 807                                    &fixup_nodatasum->work);
 808                 goto out;
 809         }
 810
 811         /*
 812          * now build and submit the bios for the other mirrors, check
 813          * checksums
 814          */
 815         for (mirror_index = 0;
 816              mirror_index < BTRFS_MAX_MIRRORS &&
 817              sblocks_for_recheck[mirror_index].page_count > 0;
 818              mirror_index++) {
 819                 if (mirror_index == failed_mirror_index)
 820                         continue;
 821
 822                 /* build and submit the bios, check checksums */
 823                 ret = scrub_recheck_block(fs_info,
 824                                           sblocks_for_recheck + mirror_index,
 825                                           is_metadata, have_csum, csum,
 826                                           generation, sctx->csum_size);
 827                 if (ret)
 828                         goto did_not_correct_error;
 829         }
 830
 831         /*
 832          * first try to pick the mirror which is completely without I/O
 833          * errors and also does not have a checksum error.
 834          * If one is found, and if a checksum is present, the full block
 835          * that is known to contain an error is rewritten. Afterwards
 836          * the block is known to be corrected.
 837          * If a mirror is found which is completely correct, and no
 838          * checksum is present, only those pages are rewritten that had
 839          * an I/O error in the block to be repaired, since it cannot be
 840          * determined, which copy of the other pages is better (and it
 841          * could happen otherwise that a correct page would be
 842          * overwritten by a bad one).
 843          */
 844         for (mirror_index = 0;
 845              mirror_index < BTRFS_MAX_MIRRORS &&
 846              sblocks_for_recheck[mirror_index].page_count > 0;
 847              mirror_index++) {
 848                 struct scrub_block *sblock_other = sblocks_for_recheck +
 849                                                    mirror_index;
 850
 851                 if (!sblock_other->header_error &&
 852                     !sblock_other->checksum_error &&
 853                     sblock_other->no_io_error_seen) {
 854                         int force_write = is_metadata || have_csum;
 855
 856                         ret = scrub_repair_block_from_good_copy(sblock_bad,
 857                                                                 sblock_other,
 858                                                                 force_write);
 859                         if (0 == ret)
 860                                 goto corrected_error;
 861                 }
 862         }
 863
 864         /*
 865          * in case of I/O errors in the area that is supposed to be
 866          * repaired, continue by picking good copies of those pages.
 867          * Select the good pages from mirrors to rewrite bad pages from
 868          * the area to fix. Afterwards verify the checksum of the block
 869          * that is supposed to be repaired. This verification step is
 870          * only done for the purpose of statistic counting and for the
 871          * final scrub report, whether errors remain.
 872          * A perfect algorithm could make use of the checksum and try
 873          * all possible combinations of pages from the different mirrors
 874          * until the checksum verification succeeds. For example, when
 875          * the 2nd page of mirror #1 faces I/O errors, and the 2nd page
 876          * of mirror #2 is readable but the final checksum test fails,
 877          * then the 2nd page of mirror #3 could be tried, whether now
 878          * the final checksum succeedes. But this would be a rare
 879          * exception and is therefore not implemented. At least it is
 880          * avoided that the good copy is overwritten.
 881          * A more useful improvement would be to pick the sectors
 882          * without I/O error based on sector sizes (512 bytes on legacy
 883          * disks) instead of on PAGE_SIZE. Then maybe 512 byte of one
 884          * mirror could be repaired by taking 512 byte of a different
 885          * mirror, even if other 512 byte sectors in the same PAGE_SIZE
 886          * area are unreadable.
 887          */
 888
 889         /* can only fix I/O errors from here on */
 890         if (sblock_bad->no_io_error_seen)
 891                 goto did_not_correct_error;
 892
 893         success = 1;
 894         for (page_num = 0; page_num < sblock_bad->page_count; page_num++) {
 895                 struct scrub_page *page_bad = sblock_bad->pagev + page_num;
 896
 897                 if (!page_bad->io_error)
 898                         continue;
 899
 900                 for (mirror_index = 0;
 901                      mirror_index < BTRFS_MAX_MIRRORS &&
 902                      sblocks_for_recheck[mirror_index].page_count > 0;
 903                      mirror_index++) {
 904                         struct scrub_block *sblock_other = sblocks_for_recheck +
 905                                                            mirror_index;
 906                         struct scrub_page *page_other = sblock_other->pagev +
 907                                                         page_num;
 908
 909                         if (!page_other->io_error) {
 910                                 ret = scrub_repair_page_from_good_copy(
 911                                         sblock_bad, sblock_other, page_num, 0);
 912                                 if (0 == ret) {
 913                                         page_bad->io_error = 0;
 914                                         break; /* succeeded for this page */
 915                                 }
 916                         }
 917                 }
 918
 919                 if (page_bad->io_error) {
 920                         /* did not find a mirror to copy the page from */
 921                         success = 0;
 922                 }
 923         }
 924
 925         if (success) {
 926                 if (is_metadata || have_csum) {
 927                         /*
 928                          * need to verify the checksum now that all
 929                          * sectors on disk are repaired (the write
 930                          * request for data to be repaired is on its way).
 931                          * Just be lazy and use scrub_recheck_block()
 932                          * which re-reads the data before the checksum
 933                          * is verified, but most likely the data comes out
 934                          * of the page cache.
 935                          */
 936                         ret = scrub_recheck_block(fs_info, sblock_bad,
 937                                                   is_metadata, have_csum, csum,
 938                                                   generation, sctx->csum_size);
 939                         if (!ret && !sblock_bad->header_error &&
 940                             !sblock_bad->checksum_error &&
 941                             sblock_bad->no_io_error_seen)
 942                                 goto corrected_error;
 943                         else
 944                                 goto did_not_correct_error;
 945                 } else {
 946 corrected_error:
 947                         spin_lock(&sctx->stat_lock);
 948                         sctx->stat.corrected_errors++;
 949                         spin_unlock(&sctx->stat_lock);
 950                         printk_ratelimited_in_rcu(KERN_ERR
 951                                 "btrfs: fixed up error at logical %llu on dev %s\n",
 952                                 (unsigned long long)logical,
 953                                 rcu_str_deref(dev->name));
 954                 }
 955         } else {
 956 did_not_correct_error:
 957                 spin_lock(&sctx->stat_lock);
 958                 sctx->stat.uncorrectable_errors++;
 959                 spin_unlock(&sctx->stat_lock);
 960                 printk_ratelimited_in_rcu(KERN_ERR
 961                         "btrfs: unable to fixup (regular) error at logical %llu on dev %s\n",
 962                         (unsigned long long)logical,
 963                         rcu_str_deref(dev->name));
 964         }
 965
 966 out:
 967         if (sblocks_for_recheck) {
 968                 for (mirror_index = 0; mirror_index < BTRFS_MAX_MIRRORS;
 969                      mirror_index++) {
 970                         struct scrub_block *sblock = sblocks_for_recheck +
 971                                                      mirror_index;
 972                         int page_index;
 973
 974                         for (page_index = 0; page_index < SCRUB_PAGES_PER_BIO;
 975                              page_index++)
 976                                 if (sblock->pagev[page_index].page)
 977                                         __free_page(
 978                                                 sblock->pagev[page_index].page);
 979                 }
 980                 kfree(sblocks_for_recheck);
 981         }
 982
 983         return 0;
 984 }
 985
 986 static int scrub_setup_recheck_block(struct scrub_ctx *sctx,
 987                                      struct btrfs_mapping_tree *map_tree,
 988                                      u64 length, u64 logical,
 989                                      struct scrub_block *sblocks_for_recheck)
 990 {
 991         int page_index;
 992         int mirror_index;
 993         int ret;
 994
 995         /*
 996          * note: the three members sctx, ref_count and outstanding_pages
 997          * are not used (and not set) in the blocks that are used for
 998          * the recheck procedure
 999          */
1000
1001         page_index = 0;
1002         while (length > 0) {
1003                 u64 sublen = min_t(u64, length, PAGE_SIZE);
1004                 u64 mapped_length = sublen;
1005                 struct btrfs_bio *bbio = NULL;
1006
1007                 /*
1008                  * with a length of PAGE_SIZE, each returned stripe
1009                  * represents one mirror
1010                  */
1011                 ret = btrfs_map_block(map_tree, WRITE, logical, &mapped_length,
1012                                       &bbio, 0);
1013                 if (ret || !bbio || mapped_length < sublen) {
1014                         kfree(bbio);
1015                         return -EIO;
1016                 }
1017
1018                 BUG_ON(page_index >= SCRUB_PAGES_PER_BIO);
1019                 for (mirror_index = 0; mirror_index < (int)bbio->num_stripes;
1020                      mirror_index++) {
1021                         struct scrub_block *sblock;
1022                         struct scrub_page *page;
1023
1024                         if (mirror_index >= BTRFS_MAX_MIRRORS)
1025                                 continue;
1026
1027                         sblock = sblocks_for_recheck + mirror_index;
1028                         page = sblock->pagev + page_index;
1029                         page->logical = logical;
1030                         page->physical = bbio->stripes[mirror_index].physical;
1031                         /* for missing devices, dev->bdev is NULL */
1032                         page->dev = bbio->stripes[mirror_index].dev;
1033                         page->mirror_num = mirror_index + 1;
1034                         page->page = alloc_page(GFP_NOFS);
1035                         if (!page->page) {
1036                                 spin_lock(&sctx->stat_lock);
1037                                 sctx->stat.malloc_errors++;
1038                                 spin_unlock(&sctx->stat_lock);
1039                                 kfree(bbio);
1040                                 return -ENOMEM;
1041                         }
1042                         sblock->page_count++;
1043                 }
1044                 kfree(bbio);
1045                 length -= sublen;
1046                 logical += sublen;
1047                 page_index++;
1048         }
1049
1050         return 0;
1051 }
1052
1053 /*
1054  * this function will check the on disk data for checksum errors, header
1055  * errors and read I/O errors. If any I/O errors happen, the exact pages
1056  * which are errored are marked as being bad. The goal is to enable scrub
1057  * to take those pages that are not errored from all the mirrors so that
1058  * the pages that are errored in the just handled mirror can be repaired.
1059  */
1060 static int scrub_recheck_block(struct btrfs_fs_info *fs_info,
1061                                struct scrub_block *sblock, int is_metadata,
1062                                int have_csum, u8 *csum, u64 generation,
1063                                u16 csum_size)
1064 {
1065         int page_num;
1066
1067         sblock->no_io_error_seen = 1;
1068         sblock->header_error = 0;
1069         sblock->checksum_error = 0;
1070
1071         for (page_num = 0; page_num < sblock->page_count; page_num++) {
1072                 struct bio *bio;
1073                 int ret;
1074                 struct scrub_page *page = sblock->pagev + page_num;
1075                 DECLARE_COMPLETION_ONSTACK(complete);
1076
1077                 if (page->dev->bdev == NULL) {
1078                         page->io_error = 1;
1079                         sblock->no_io_error_seen = 0;
1080                         continue;
1081                 }
1082
1083                 BUG_ON(!page->page);
1084                 bio = bio_alloc(GFP_NOFS, 1);
1085                 if (!bio)
1086                         return -EIO;
1087                 bio->bi_bdev = page->dev->bdev;
1088                 bio->bi_sector = page->physical >> 9;
1089                 bio->bi_end_io = scrub_complete_bio_end_io;
1090                 bio->bi_private = &complete;
1091
1092                 ret = bio_add_page(bio, page->page, PAGE_SIZE, 0);
1093                 if (PAGE_SIZE != ret) {
1094                         bio_put(bio);
1095                         return -EIO;
1096                 }
1097                 btrfsic_submit_bio(READ, bio);
1098
1099                 /* this will also unplug the queue */
1100                 wait_for_completion(&complete);
1101
1102                 page->io_error = !test_bit(BIO_UPTODATE, &bio->bi_flags);
1103                 if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
1104                         sblock->no_io_error_seen = 0;
1105                 bio_put(bio);
1106         }
1107
1108         if (sblock->no_io_error_seen)
1109                 scrub_recheck_block_checksum(fs_info, sblock, is_metadata,
1110                                              have_csum, csum, generation,
1111                                              csum_size);
1112
1113         return 0;
1114 }
1115
1116 static void scrub_recheck_block_checksum(struct btrfs_fs_info *fs_info,
1117                                          struct scrub_block *sblock,
1118                                          int is_metadata, int have_csum,
1119                                          const u8 *csum, u64 generation,
1120                                          u16 csum_size)
1121 {
1122         int page_num;
1123         u8 calculated_csum[BTRFS_CSUM_SIZE];
1124         u32 crc = ~(u32)0;
1125         struct btrfs_root *root = fs_info->extent_root;
1126         void *mapped_buffer;
1127
1128         BUG_ON(!sblock->pagev[0].page);
1129         if (is_metadata) {
1130                 struct btrfs_header *h;
1131
1132                 mapped_buffer = kmap_atomic(sblock->pagev[0].page);
1133                 h = (struct btrfs_header *)mapped_buffer;
1134
1135                 if (sblock->pagev[0].logical != le64_to_cpu(h->bytenr) ||
1136                     memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE) ||
1137                     memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
1138                            BTRFS_UUID_SIZE)) {
1139                         sblock->header_error = 1;
1140                 } else if (generation != le64_to_cpu(h->generation)) {
1141                         sblock->header_error = 1;
1142                         sblock->generation_error = 1;
1143                 }
1144                 csum = h->csum;
1145         } else {
1146                 if (!have_csum)
1147                         return;
1148
1149                 mapped_buffer = kmap_atomic(sblock->pagev[0].page);
1150         }
1151
1152         for (page_num = 0;;) {
1153                 if (page_num == 0 && is_metadata)
1154                         crc = btrfs_csum_data(root,
1155                                 ((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE,
1156                                 crc, PAGE_SIZE - BTRFS_CSUM_SIZE);
1157                 else
1158                         crc = btrfs_csum_data(root, mapped_buffer, crc,
1159                                               PAGE_SIZE);
1160
1161                 kunmap_atomic(mapped_buffer);
1162                 page_num++;
1163                 if (page_num >= sblock->page_count)
1164                         break;
1165                 BUG_ON(!sblock->pagev[page_num].page);
1166
1167                 mapped_buffer = kmap_atomic(sblock->pagev[page_num].page);
1168         }
1169
1170         btrfs_csum_final(crc, calculated_csum);
1171         if (memcmp(calculated_csum, csum, csum_size))
1172                 sblock->checksum_error = 1;
1173 }
1174
1175 static void scrub_complete_bio_end_io(struct bio *bio, int err)
1176 {
1177         complete((struct completion *)bio->bi_private);
1178 }
1179
1180 static int scrub_repair_block_from_good_copy(struct scrub_block *sblock_bad,
1181                                              struct scrub_block *sblock_good,
1182                                              int force_write)
1183 {
1184         int page_num;
1185         int ret = 0;
1186
1187         for (page_num = 0; page_num < sblock_bad->page_count; page_num++) {
1188                 int ret_sub;
1189
1190                 ret_sub = scrub_repair_page_from_good_copy(sblock_bad,
1191                                                            sblock_good,
1192                                                            page_num,
1193                                                            force_write);
1194                 if (ret_sub)
1195                         ret = ret_sub;
1196         }
1197
1198         return ret;
1199 }
1200
1201 static int scrub_repair_page_from_good_copy(struct scrub_block *sblock_bad,
1202                                             struct scrub_block *sblock_good,
1203                                             int page_num, int force_write)
1204 {
1205         struct scrub_page *page_bad = sblock_bad->pagev + page_num;
1206         struct scrub_page *page_good = sblock_good->pagev + page_num;
1207
1208         BUG_ON(sblock_bad->pagev[page_num].page == NULL);
1209         BUG_ON(sblock_good->pagev[page_num].page == NULL);
1210         if (force_write || sblock_bad->header_error ||
1211             sblock_bad->checksum_error || page_bad->io_error) {
1212                 struct bio *bio;
1213                 int ret;
1214                 DECLARE_COMPLETION_ONSTACK(complete);
1215
1216                 bio = bio_alloc(GFP_NOFS, 1);
1217                 if (!bio)
1218                         return -EIO;
1219                 bio->bi_bdev = page_bad->dev->bdev;
1220                 bio->bi_sector = page_bad->physical >> 9;
1221                 bio->bi_end_io = scrub_complete_bio_end_io;
1222                 bio->bi_private = &complete;
1223
1224                 ret = bio_add_page(bio, page_good->page, PAGE_SIZE, 0);
1225                 if (PAGE_SIZE != ret) {
1226                         bio_put(bio);
1227                         return -EIO;
1228                 }
1229                 btrfsic_submit_bio(WRITE, bio);
1230
1231                 /* this will also unplug the queue */
1232                 wait_for_completion(&complete);
1233                 if (!bio_flagged(bio, BIO_UPTODATE)) {
1234                         btrfs_dev_stat_inc_and_print(page_bad->dev,
1235                                 BTRFS_DEV_STAT_WRITE_ERRS);
1236                         bio_put(bio);
1237                         return -EIO;
1238                 }
1239                 bio_put(bio);
1240         }
1241
1242         return 0;
1243 }
1244
1245 static void scrub_checksum(struct scrub_block *sblock)
1246 {
1247         u64 flags;
1248         int ret;
1249
1250         BUG_ON(sblock->page_count < 1);
1251         flags = sblock->pagev[0].flags;
1252         ret = 0;
1253         if (flags & BTRFS_EXTENT_FLAG_DATA)
1254                 ret = scrub_checksum_data(sblock);
1255         else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)
1256                 ret = scrub_checksum_tree_block(sblock);
1257         else if (flags & BTRFS_EXTENT_FLAG_SUPER)
1258                 (void)scrub_checksum_super(sblock);
1259         else
1260                 WARN_ON(1);
1261         if (ret)
1262                 scrub_handle_errored_block(sblock);
1263 }
1264
1265 static int scrub_checksum_data(struct scrub_block *sblock)
1266 {
1267         struct scrub_ctx *sctx = sblock->sctx;
1268         u8 csum[BTRFS_CSUM_SIZE];
1269         u8 *on_disk_csum;
1270         struct page *page;
1271         void *buffer;
1272         u32 crc = ~(u32)0;
1273         int fail = 0;
1274         struct btrfs_root *root = sctx->dev_root;
1275         u64 len;
1276         int index;
1277
1278         BUG_ON(sblock->page_count < 1);
1279         if (!sblock->pagev[0].have_csum)
1280                 return 0;
1281
1282         on_disk_csum = sblock->pagev[0].csum;
1283         page = sblock->pagev[0].page;
1284         buffer = kmap_atomic(page);
1285
1286         len = sctx->sectorsize;
1287         index = 0;
1288         for (;;) {
1289                 u64 l = min_t(u64, len, PAGE_SIZE);
1290
1291                 crc = btrfs_csum_data(root, buffer, crc, l);
1292                 kunmap_atomic(buffer);
1293                 len -= l;
1294                 if (len == 0)
1295                         break;
1296                 index++;
1297                 BUG_ON(index >= sblock->page_count);
1298                 BUG_ON(!sblock->pagev[index].page);
1299                 page = sblock->pagev[index].page;
1300                 buffer = kmap_atomic(page);
1301         }
1302
1303         btrfs_csum_final(crc, csum);
1304         if (memcmp(csum, on_disk_csum, sctx->csum_size))
1305                 fail = 1;
1306
1307         return fail;
1308 }
1309
1310 static int scrub_checksum_tree_block(struct scrub_block *sblock)
1311 {
1312         struct scrub_ctx *sctx = sblock->sctx;
1313         struct btrfs_header *h;
1314         struct btrfs_root *root = sctx->dev_root;
1315         struct btrfs_fs_info *fs_info = root->fs_info;
1316         u8 calculated_csum[BTRFS_CSUM_SIZE];
1317         u8 on_disk_csum[BTRFS_CSUM_SIZE];
1318         struct page *page;
1319         void *mapped_buffer;
1320         u64 mapped_size;
1321         void *p;
1322         u32 crc = ~(u32)0;
1323         int fail = 0;
1324         int crc_fail = 0;
1325         u64 len;
1326         int index;
1327
1328         BUG_ON(sblock->page_count < 1);
1329         page = sblock->pagev[0].page;
1330         mapped_buffer = kmap_atomic(page);
1331         h = (struct btrfs_header *)mapped_buffer;
1332         memcpy(on_disk_csum, h->csum, sctx->csum_size);
1333
1334         /*
1335          * we don't use the getter functions here, as we
1336          * a) don't have an extent buffer and
1337          * b) the page is already kmapped
1338          */
1339
1340         if (sblock->pagev[0].logical != le64_to_cpu(h->bytenr))
1341                 ++fail;
1342
1343         if (sblock->pagev[0].generation != le64_to_cpu(h->generation))
1344                 ++fail;
1345
1346         if (memcmp(h->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
1347                 ++fail;
1348
1349         if (memcmp(h->chunk_tree_uuid, fs_info->chunk_tree_uuid,
1350                    BTRFS_UUID_SIZE))
1351                 ++fail;
1352
1353         BUG_ON(sctx->nodesize != sctx->leafsize);
1354         len = sctx->nodesize - BTRFS_CSUM_SIZE;
1355         mapped_size = PAGE_SIZE - BTRFS_CSUM_SIZE;
1356         p = ((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE;
1357         index = 0;
1358         for (;;) {
1359                 u64 l = min_t(u64, len, mapped_size);
1360
1361                 crc = btrfs_csum_data(root, p, crc, l);
1362                 kunmap_atomic(mapped_buffer);
1363                 len -= l;
1364                 if (len == 0)
1365                         break;
1366                 index++;
1367                 BUG_ON(index >= sblock->page_count);
1368                 BUG_ON(!sblock->pagev[index].page);
1369                 page = sblock->pagev[index].page;
1370                 mapped_buffer = kmap_atomic(page);
1371                 mapped_size = PAGE_SIZE;
1372                 p = mapped_buffer;
1373         }
1374
1375         btrfs_csum_final(crc, calculated_csum);
1376         if (memcmp(calculated_csum, on_disk_csum, sctx->csum_size))
1377                 ++crc_fail;
1378
1379         return fail || crc_fail;
1380 }
1381
1382 static int scrub_checksum_super(struct scrub_block *sblock)
1383 {
1384         struct btrfs_super_block *s;
1385         struct scrub_ctx *sctx = sblock->sctx;
1386         struct btrfs_root *root = sctx->dev_root;
1387         struct btrfs_fs_info *fs_info = root->fs_info;
1388         u8 calculated_csum[BTRFS_CSUM_SIZE];
1389         u8 on_disk_csum[BTRFS_CSUM_SIZE];
1390         struct page *page;
1391         void *mapped_buffer;
1392         u64 mapped_size;
1393         void *p;
1394         u32 crc = ~(u32)0;
1395         int fail_gen = 0;
1396         int fail_cor = 0;
1397         u64 len;
1398         int index;
1399
1400         BUG_ON(sblock->page_count < 1);
1401         page = sblock->pagev[0].page;
1402         mapped_buffer = kmap_atomic(page);
1403         s = (struct btrfs_super_block *)mapped_buffer;
1404         memcpy(on_disk_csum, s->csum, sctx->csum_size);
1405
1406         if (sblock->pagev[0].logical != le64_to_cpu(s->bytenr))
1407                 ++fail_cor;
1408
1409         if (sblock->pagev[0].generation != le64_to_cpu(s->generation))
1410                 ++fail_gen;
1411
1412         if (memcmp(s->fsid, fs_info->fsid, BTRFS_UUID_SIZE))
1413                 ++fail_cor;
1414
1415         len = BTRFS_SUPER_INFO_SIZE - BTRFS_CSUM_SIZE;
1416         mapped_size = PAGE_SIZE - BTRFS_CSUM_SIZE;
1417         p = ((u8 *)mapped_buffer) + BTRFS_CSUM_SIZE;
1418         index = 0;
1419         for (;;) {
1420                 u64 l = min_t(u64, len, mapped_size);
1421
1422                 crc = btrfs_csum_data(root, p, crc, l);
1423                 kunmap_atomic(mapped_buffer);
1424                 len -= l;
1425                 if (len == 0)
1426                         break;
1427                 index++;
1428                 BUG_ON(index >= sblock->page_count);
1429                 BUG_ON(!sblock->pagev[index].page);
1430                 page = sblock->pagev[index].page;
1431                 mapped_buffer = kmap_atomic(page);
1432                 mapped_size = PAGE_SIZE;
1433                 p = mapped_buffer;
1434         }
1435
1436         btrfs_csum_final(crc, calculated_csum);
1437         if (memcmp(calculated_csum, on_disk_csum, sctx->csum_size))
1438                 ++fail_cor;
1439
1440         if (fail_cor + fail_gen) {
1441                 /*
1442                  * if we find an error in a super block, we just report it.
1443                  * They will get written with the next transaction commit
1444                  * anyway
1445                  */
1446                 spin_lock(&sctx->stat_lock);
1447                 ++sctx->stat.super_errors;
1448                 spin_unlock(&sctx->stat_lock);
1449                 if (fail_cor)
1450                         btrfs_dev_stat_inc_and_print(sblock->pagev[0].dev,
1451                                 BTRFS_DEV_STAT_CORRUPTION_ERRS);
1452                 else
1453                         btrfs_dev_stat_inc_and_print(sblock->pagev[0].dev,
1454                                 BTRFS_DEV_STAT_GENERATION_ERRS);
1455         }
1456
1457         return fail_cor + fail_gen;
1458 }
1459
1460 static void scrub_block_get(struct scrub_block *sblock)
1461 {
1462         atomic_inc(&sblock->ref_count);
1463 }
1464
1465 static void scrub_block_put(struct scrub_block *sblock)
1466 {
1467         if (atomic_dec_and_test(&sblock->ref_count)) {
1468                 int i;
1469
1470                 for (i = 0; i < sblock->page_count; i++)
1471                         if (sblock->pagev[i].page)
1472                                 __free_page(sblock->pagev[i].page);
1473                 kfree(sblock);
1474         }
1475 }
1476
1477 static void scrub_submit(struct scrub_ctx *sctx)
1478 {
1479         struct scrub_bio *sbio;
1480
1481         if (sctx->curr == -1)
1482                 return;
1483
1484         sbio = sctx->bios[sctx->curr];
1485         sctx->curr = -1;
1486         atomic_inc(&sctx->in_flight);
1487
1488         btrfsic_submit_bio(READ, sbio->bio);
1489 }
1490
1491 static int scrub_add_page_to_bio(struct scrub_ctx *sctx,
1492                                  struct scrub_page *spage)
1493 {
1494         struct scrub_block *sblock = spage->sblock;
1495         struct scrub_bio *sbio;
1496         int ret;
1497
1498 again:
1499         /*
1500          * grab a fresh bio or wait for one to become available
1501          */
1502         while (sctx->curr == -1) {
1503                 spin_lock(&sctx->list_lock);
1504                 sctx->curr = sctx->first_free;
1505                 if (sctx->curr != -1) {
1506                         sctx->first_free = sctx->bios[sctx->curr]->next_free;
1507                         sctx->bios[sctx->curr]->next_free = -1;
1508                         sctx->bios[sctx->curr]->page_count = 0;
1509                         spin_unlock(&sctx->list_lock);
1510                 } else {
1511                         spin_unlock(&sctx->list_lock);
1512                         wait_event(sctx->list_wait, sctx->first_free != -1);
1513                 }
1514         }
1515         sbio = sctx->bios[sctx->curr];
1516         if (sbio->page_count == 0) {
1517                 struct bio *bio;
1518
1519                 sbio->physical = spage->physical;
1520                 sbio->logical = spage->logical;
1521                 sbio->dev = spage->dev;
1522                 bio = sbio->bio;
1523                 if (!bio) {
1524                         bio = bio_alloc(GFP_NOFS, sctx->pages_per_bio);
1525                         if (!bio)
1526                                 return -ENOMEM;
1527                         sbio->bio = bio;
1528                 }
1529
1530                 bio->bi_private = sbio;
1531                 bio->bi_end_io = scrub_bio_end_io;
1532                 bio->bi_bdev = sbio->dev->bdev;
1533                 bio->bi_sector = sbio->physical >> 9;
1534                 sbio->err = 0;
1535         } else if (sbio->physical + sbio->page_count * PAGE_SIZE !=
1536                    spage->physical ||
1537                    sbio->logical + sbio->page_count * PAGE_SIZE !=
1538                    spage->logical ||
1539                    sbio->dev != spage->dev) {
1540                 scrub_submit(sctx);
1541                 goto again;
1542         }
1543
1544         sbio->pagev[sbio->page_count] = spage;
1545         ret = bio_add_page(sbio->bio, spage->page, PAGE_SIZE, 0);
1546         if (ret != PAGE_SIZE) {
1547                 if (sbio->page_count < 1) {
1548                         bio_put(sbio->bio);
1549                         sbio->bio = NULL;
1550                         return -EIO;
1551                 }
1552                 scrub_submit(sctx);
1553                 goto again;
1554         }
1555
1556         scrub_block_get(sblock); /* one for the added page */
1557         atomic_inc(&sblock->outstanding_pages);
1558         sbio->page_count++;
1559         if (sbio->page_count == sctx->pages_per_bio)
1560                 scrub_submit(sctx);
1561
1562         return 0;
1563 }
1564
1565 static int scrub_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
1566                        u64 physical, struct btrfs_device *dev, u64 flags,
1567                        u64 gen, int mirror_num, u8 *csum, int force)
1568 {
1569         struct scrub_block *sblock;
1570         int index;
1571
1572         sblock = kzalloc(sizeof(*sblock), GFP_NOFS);
1573         if (!sblock) {
1574                 spin_lock(&sctx->stat_lock);
1575                 sctx->stat.malloc_errors++;
1576                 spin_unlock(&sctx->stat_lock);
1577                 return -ENOMEM;
1578         }
1579
1580         /* one ref inside this function, plus one for each page later on */
1581         atomic_set(&sblock->ref_count, 1);
1582         sblock->sctx = sctx;
1583         sblock->no_io_error_seen = 1;
1584
1585         for (index = 0; len > 0; index++) {
1586                 struct scrub_page *spage = sblock->pagev + index;
1587                 u64 l = min_t(u64, len, PAGE_SIZE);
1588
1589                 BUG_ON(index >= SCRUB_MAX_PAGES_PER_BLOCK);
1590                 spage->page = alloc_page(GFP_NOFS);
1591                 if (!spage->page) {
1592                         spin_lock(&sctx->stat_lock);
1593                         sctx->stat.malloc_errors++;
1594                         spin_unlock(&sctx->stat_lock);
1595                         while (index > 0) {
1596                                 index--;
1597                                 __free_page(sblock->pagev[index].page);
1598                         }
1599                         kfree(sblock);
1600                         return -ENOMEM;
1601                 }
1602                 spage->sblock = sblock;
1603                 spage->dev = dev;
1604                 spage->flags = flags;
1605                 spage->generation = gen;
1606                 spage->logical = logical;
1607                 spage->physical = physical;
1608                 spage->mirror_num = mirror_num;
1609                 if (csum) {
1610                         spage->have_csum = 1;
1611                         memcpy(spage->csum, csum, sctx->csum_size);
1612                 } else {
1613                         spage->have_csum = 0;
1614                 }
1615                 sblock->page_count++;
1616                 len -= l;
1617                 logical += l;
1618                 physical += l;
1619         }
1620
1621         BUG_ON(sblock->page_count == 0);
1622         for (index = 0; index < sblock->page_count; index++) {
1623                 struct scrub_page *spage = sblock->pagev + index;
1624                 int ret;
1625
1626                 ret = scrub_add_page_to_bio(sctx, spage);
1627                 if (ret) {
1628                         scrub_block_put(sblock);
1629                         return ret;
1630                 }
1631         }
1632
1633         if (force)
1634                 scrub_submit(sctx);
1635
1636         /* last one frees, either here or in bio completion for last page */
1637         scrub_block_put(sblock);
1638         return 0;
1639 }
1640
1641 static void scrub_bio_end_io(struct bio *bio, int err)
1642 {
1643         struct scrub_bio *sbio = bio->bi_private;
1644         struct btrfs_fs_info *fs_info = sbio->dev->dev_root->fs_info;
1645
1646         sbio->err = err;
1647         sbio->bio = bio;
1648
1649         btrfs_queue_worker(&fs_info->scrub_workers, &sbio->work);
1650 }
1651
1652 static void scrub_bio_end_io_worker(struct btrfs_work *work)
1653 {
1654         struct scrub_bio *sbio = container_of(work, struct scrub_bio, work);
1655         struct scrub_ctx *sctx = sbio->sctx;
1656         int i;
1657
1658         BUG_ON(sbio->page_count > SCRUB_PAGES_PER_BIO);
1659         if (sbio->err) {
1660                 for (i = 0; i < sbio->page_count; i++) {
1661                         struct scrub_page *spage = sbio->pagev[i];
1662
1663                         spage->io_error = 1;
1664                         spage->sblock->no_io_error_seen = 0;
1665                 }
1666         }
1667
1668         /* now complete the scrub_block items that have all pages completed */
1669         for (i = 0; i < sbio->page_count; i++) {
1670                 struct scrub_page *spage = sbio->pagev[i];
1671                 struct scrub_block *sblock = spage->sblock;
1672
1673                 if (atomic_dec_and_test(&sblock->outstanding_pages))
1674                         scrub_block_complete(sblock);
1675                 scrub_block_put(sblock);
1676         }
1677
1678         bio_put(sbio->bio);
1679         sbio->bio = NULL;
1680         spin_lock(&sctx->list_lock);
1681         sbio->next_free = sctx->first_free;
1682         sctx->first_free = sbio->index;
1683         spin_unlock(&sctx->list_lock);
1684         atomic_dec(&sctx->in_flight);
1685         wake_up(&sctx->list_wait);
1686 }
1687
1688 static void scrub_block_complete(struct scrub_block *sblock)
1689 {
1690         if (!sblock->no_io_error_seen)
1691                 scrub_handle_errored_block(sblock);
1692         else
1693                 scrub_checksum(sblock);
1694 }
1695
1696 static int scrub_find_csum(struct scrub_ctx *sctx, u64 logical, u64 len,
1697                            u8 *csum)
1698 {
1699         struct btrfs_ordered_sum *sum = NULL;
1700         int ret = 0;
1701         unsigned long i;
1702         unsigned long num_sectors;
1703
1704         while (!list_empty(&sctx->csum_list)) {
1705                 sum = list_first_entry(&sctx->csum_list,
1706                                        struct btrfs_ordered_sum, list);
1707                 if (sum->bytenr > logical)
1708                         return 0;
1709                 if (sum->bytenr + sum->len > logical)
1710                         break;
1711
1712                 ++sctx->stat.csum_discards;
1713                 list_del(&sum->list);
1714                 kfree(sum);
1715                 sum = NULL;
1716         }
1717         if (!sum)
1718                 return 0;
1719
1720         num_sectors = sum->len / sctx->sectorsize;
1721         for (i = 0; i < num_sectors; ++i) {
1722                 if (sum->sums[i].bytenr == logical) {
1723                         memcpy(csum, &sum->sums[i].sum, sctx->csum_size);
1724                         ret = 1;
1725                         break;
1726                 }
1727         }
1728         if (ret && i == num_sectors - 1) {
1729                 list_del(&sum->list);
1730                 kfree(sum);
1731         }
1732         return ret;
1733 }
1734
1735 /* scrub extent tries to collect up to 64 kB for each bio */
1736 static int scrub_extent(struct scrub_ctx *sctx, u64 logical, u64 len,
1737                         u64 physical, struct btrfs_device *dev, u64 flags,
1738                         u64 gen, int mirror_num)
1739 {
1740         int ret;
1741         u8 csum[BTRFS_CSUM_SIZE];
1742         u32 blocksize;
1743
1744         if (flags & BTRFS_EXTENT_FLAG_DATA) {
1745                 blocksize = sctx->sectorsize;
1746                 spin_lock(&sctx->stat_lock);
1747                 sctx->stat.data_extents_scrubbed++;
1748                 sctx->stat.data_bytes_scrubbed += len;
1749                 spin_unlock(&sctx->stat_lock);
1750         } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
1751                 BUG_ON(sctx->nodesize != sctx->leafsize);
1752                 blocksize = sctx->nodesize;
1753                 spin_lock(&sctx->stat_lock);
1754                 sctx->stat.tree_extents_scrubbed++;
1755                 sctx->stat.tree_bytes_scrubbed += len;
1756                 spin_unlock(&sctx->stat_lock);
1757         } else {
1758                 blocksize = sctx->sectorsize;
1759                 BUG_ON(1);
1760         }
1761
1762         while (len) {
1763                 u64 l = min_t(u64, len, blocksize);
1764                 int have_csum = 0;
1765
1766                 if (flags & BTRFS_EXTENT_FLAG_DATA) {
1767                         /* push csums to sbio */
1768                         have_csum = scrub_find_csum(sctx, logical, l, csum);
1769                         if (have_csum == 0)
1770                                 ++sctx->stat.no_csum;
1771                 }
1772                 ret = scrub_pages(sctx, logical, l, physical, dev, flags, gen,
1773                                   mirror_num, have_csum ? csum : NULL, 0);
1774                 if (ret)
1775                         return ret;
1776                 len -= l;
1777                 logical += l;
1778                 physical += l;
1779         }
1780         return 0;
1781 }
1782
1783 static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
1784                                            struct map_lookup *map,
1785                                            struct btrfs_device *scrub_dev,
1786                                            int num, u64 base, u64 length)
1787 {
1788         struct btrfs_path *path;
1789         struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
1790         struct btrfs_root *root = fs_info->extent_root;
1791         struct btrfs_root *csum_root = fs_info->csum_root;
1792         struct btrfs_extent_item *extent;
1793         struct blk_plug plug;
1794         u64 flags;
1795         int ret;
1796         int slot;
1797         int i;
1798         u64 nstripes;
1799         struct extent_buffer *l;
1800         struct btrfs_key key;
1801         u64 physical;
1802         u64 logical;
1803         u64 generation;
1804         int mirror_num;
1805         struct reada_control *reada1;
1806         struct reada_control *reada2;
1807         struct btrfs_key key_start;
1808         struct btrfs_key key_end;
1809         u64 increment = map->stripe_len;
1810         u64 offset;
1811
1812         nstripes = length;
1813         offset = 0;
1814         do_div(nstripes, map->stripe_len);
1815         if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
1816                 offset = map->stripe_len * num;
1817                 increment = map->stripe_len * map->num_stripes;
1818                 mirror_num = 1;
1819         } else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
1820                 int factor = map->num_stripes / map->sub_stripes;
1821                 offset = map->stripe_len * (num / map->sub_stripes);
1822                 increment = map->stripe_len * factor;
1823                 mirror_num = num % map->sub_stripes + 1;
1824         } else if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
1825                 increment = map->stripe_len;
1826                 mirror_num = num % map->num_stripes + 1;
1827         } else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
1828                 increment = map->stripe_len;
1829                 mirror_num = num % map->num_stripes + 1;
1830         } else {
1831                 increment = map->stripe_len;
1832                 mirror_num = 1;
1833         }
1834
1835         path = btrfs_alloc_path();
1836         if (!path)
1837                 return -ENOMEM;
1838
1839         /*
1840          * work on commit root. The related disk blocks are static as
1841          * long as COW is applied. This means, it is save to rewrite
1842          * them to repair disk errors without any race conditions
1843          */
1844         path->search_commit_root = 1;
1845         path->skip_locking = 1;
1846
1847         /*
1848          * trigger the readahead for extent tree csum tree and wait for
1849          * completion. During readahead, the scrub is officially paused
1850          * to not hold off transaction commits
1851          */
1852         logical = base + offset;
1853
1854         wait_event(sctx->list_wait,
1855                    atomic_read(&sctx->in_flight) == 0);
1856         atomic_inc(&fs_info->scrubs_paused);
1857         wake_up(&fs_info->scrub_pause_wait);
1858
1859         /* FIXME it might be better to start readahead at commit root */
1860         key_start.objectid = logical;
1861         key_start.type = BTRFS_EXTENT_ITEM_KEY;
1862         key_start.offset = (u64)0;
1863         key_end.objectid = base + offset + nstripes * increment;
1864         key_end.type = BTRFS_EXTENT_ITEM_KEY;
1865         key_end.offset = (u64)0;
1866         reada1 = btrfs_reada_add(root, &key_start, &key_end);
1867
1868         key_start.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
1869         key_start.type = BTRFS_EXTENT_CSUM_KEY;
1870         key_start.offset = logical;
1871         key_end.objectid = BTRFS_EXTENT_CSUM_OBJECTID;
1872         key_end.type = BTRFS_EXTENT_CSUM_KEY;
1873         key_end.offset = base + offset + nstripes * increment;
1874         reada2 = btrfs_reada_add(csum_root, &key_start, &key_end);
1875
1876         if (!IS_ERR(reada1))
1877                 btrfs_reada_wait(reada1);
1878         if (!IS_ERR(reada2))
1879                 btrfs_reada_wait(reada2);
1880
1881         mutex_lock(&fs_info->scrub_lock);
1882         while (atomic_read(&fs_info->scrub_pause_req)) {
1883                 mutex_unlock(&fs_info->scrub_lock);
1884                 wait_event(fs_info->scrub_pause_wait,
1885                    atomic_read(&fs_info->scrub_pause_req) == 0);
1886                 mutex_lock(&fs_info->scrub_lock);
1887         }
1888         atomic_dec(&fs_info->scrubs_paused);
1889         mutex_unlock(&fs_info->scrub_lock);
1890         wake_up(&fs_info->scrub_pause_wait);
1891
1892         /*
1893          * collect all data csums for the stripe to avoid seeking during
1894          * the scrub. This might currently (crc32) end up to be about 1MB
1895          */
1896         blk_start_plug(&plug);
1897
1898         /*
1899          * now find all extents for each stripe and scrub them
1900          */
1901         logical = base + offset;
1902         physical = map->stripes[num].physical;
1903         ret = 0;
1904         for (i = 0; i < nstripes; ++i) {
1905                 /*
1906                  * canceled?
1907                  */
1908                 if (atomic_read(&fs_info->scrub_cancel_req) ||
1909                     atomic_read(&sctx->cancel_req)) {
1910                         ret = -ECANCELED;
1911                         goto out;
1912                 }
1913                 /*
1914                  * check to see if we have to pause
1915                  */
1916                 if (atomic_read(&fs_info->scrub_pause_req)) {
1917                         /* push queued extents */
1918                         scrub_submit(sctx);
1919                         wait_event(sctx->list_wait,
1920                                    atomic_read(&sctx->in_flight) == 0);
1921                         atomic_inc(&fs_info->scrubs_paused);
1922                         wake_up(&fs_info->scrub_pause_wait);
1923                         mutex_lock(&fs_info->scrub_lock);
1924                         while (atomic_read(&fs_info->scrub_pause_req)) {
1925                                 mutex_unlock(&fs_info->scrub_lock);
1926                                 wait_event(fs_info->scrub_pause_wait,
1927                                    atomic_read(&fs_info->scrub_pause_req) == 0);
1928                                 mutex_lock(&fs_info->scrub_lock);
1929                         }
1930                         atomic_dec(&fs_info->scrubs_paused);
1931                         mutex_unlock(&fs_info->scrub_lock);
1932                         wake_up(&fs_info->scrub_pause_wait);
1933                 }
1934
1935                 ret = btrfs_lookup_csums_range(csum_root, logical,
1936                                                logical + map->stripe_len - 1,
1937                                                &sctx->csum_list, 1);
1938                 if (ret)
1939                         goto out;
1940
1941                 key.objectid = logical;
1942                 key.type = BTRFS_EXTENT_ITEM_KEY;
1943                 key.offset = (u64)0;
1944
1945                 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
1946                 if (ret < 0)
1947                         goto out;
1948                 if (ret > 0) {
1949                         ret = btrfs_previous_item(root, path, 0,
1950                                                   BTRFS_EXTENT_ITEM_KEY);
1951                         if (ret < 0)
1952                                 goto out;
1953                         if (ret > 0) {
1954                                 /* there's no smaller item, so stick with the
1955                                  * larger one */
1956                                 btrfs_release_path(path);
1957                                 ret = btrfs_search_slot(NULL, root, &key,
1958                                                         path, 0, 0);
1959                                 if (ret < 0)
1960                                         goto out;
1961                         }
1962                 }
1963
1964                 while (1) {
1965                         l = path->nodes[0];
1966                         slot = path->slots[0];
1967                         if (slot >= btrfs_header_nritems(l)) {
1968                                 ret = btrfs_next_leaf(root, path);
1969                                 if (ret == 0)
1970                                         continue;
1971                                 if (ret < 0)
1972                                         goto out;
1973
1974                                 break;
1975                         }
1976                         btrfs_item_key_to_cpu(l, &key, slot);
1977
1978                         if (key.objectid + key.offset <= logical)
1979                                 goto next;
1980
1981                         if (key.objectid >= logical + map->stripe_len)
1982                                 break;
1983
1984                         if (btrfs_key_type(&key) != BTRFS_EXTENT_ITEM_KEY)
1985                                 goto next;
1986
1987                         extent = btrfs_item_ptr(l, slot,
1988                                                 struct btrfs_extent_item);
1989                         flags = btrfs_extent_flags(l, extent);
1990                         generation = btrfs_extent_generation(l, extent);
1991
1992                         if (key.objectid < logical &&
1993                             (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
1994                                 printk(KERN_ERR
1995                                        "btrfs scrub: tree block %llu spanning "
1996                                        "stripes, ignored. logical=%llu\n",
1997                                        (unsigned long long)key.objectid,
1998                                        (unsigned long long)logical);
1999                                 goto next;
2000                         }
2001
2002                         /*
2003                          * trim extent to this stripe
2004                          */
2005                         if (key.objectid < logical) {
2006                                 key.offset -= logical - key.objectid;
2007                                 key.objectid = logical;
2008                         }
2009                         if (key.objectid + key.offset >
2010                             logical + map->stripe_len) {
2011                                 key.offset = logical + map->stripe_len -
2012                                              key.objectid;
2013                         }
2014
2015                         ret = scrub_extent(sctx, key.objectid, key.offset,
2016                                            key.objectid - logical + physical,
2017                                            scrub_dev, flags, generation,
2018                                            mirror_num);
2019                         if (ret)
2020                                 goto out;
2021
2022 next:
2023                         path->slots[0]++;
2024                 }
2025                 btrfs_release_path(path);
2026                 logical += increment;
2027                 physical += map->stripe_len;
2028                 spin_lock(&sctx->stat_lock);
2029                 sctx->stat.last_physical = physical;
2030                 spin_unlock(&sctx->stat_lock);
2031         }
2032         /* push queued extents */
2033         scrub_submit(sctx);
2034
2035 out:
2036         blk_finish_plug(&plug);
2037         btrfs_free_path(path);
2038         return ret < 0 ? ret : 0;
2039 }
2040
2041 static noinline_for_stack int scrub_chunk(struct scrub_ctx *sctx,
2042                                           struct btrfs_device *scrub_dev,
2043                                           u64 chunk_tree, u64 chunk_objectid,
2044                                           u64 chunk_offset, u64 length,
2045                                           u64 dev_offset)
2046 {
2047         struct btrfs_mapping_tree *map_tree =
2048                 &sctx->dev_root->fs_info->mapping_tree;
2049         struct map_lookup *map;
2050         struct extent_map *em;
2051         int i;
2052         int ret = -EINVAL;
2053
2054         read_lock(&map_tree->map_tree.lock);
2055         em = lookup_extent_mapping(&map_tree->map_tree, chunk_offset, 1);
2056         read_unlock(&map_tree->map_tree.lock);
2057
2058         if (!em)
2059                 return -EINVAL;
2060
2061         map = (struct map_lookup *)em->bdev;
2062         if (em->start != chunk_offset)
2063                 goto out;
2064
2065         if (em->len < length)
2066                 goto out;
2067
2068         for (i = 0; i < map->num_stripes; ++i) {
2069                 if (map->stripes[i].dev->bdev == scrub_dev->bdev &&
2070                     map->stripes[i].physical == dev_offset) {
2071                         ret = scrub_stripe(sctx, map, scrub_dev, i,
2072                                            chunk_offset, length);
2073                         if (ret)
2074                                 goto out;
2075                 }
2076         }
2077 out:
2078         free_extent_map(em);
2079
2080         return ret;
2081 }
2082
2083 static noinline_for_stack
2084 int scrub_enumerate_chunks(struct scrub_ctx *sctx,
2085                            struct btrfs_device *scrub_dev, u64 start, u64 end)
2086 {
2087         struct btrfs_dev_extent *dev_extent = NULL;
2088         struct btrfs_path *path;
2089         struct btrfs_root *root = sctx->dev_root;
2090         struct btrfs_fs_info *fs_info = root->fs_info;
2091         u64 length;
2092         u64 chunk_tree;
2093         u64 chunk_objectid;
2094         u64 chunk_offset;
2095         int ret;
2096         int slot;
2097         struct extent_buffer *l;
2098         struct btrfs_key key;
2099         struct btrfs_key found_key;
2100         struct btrfs_block_group_cache *cache;
2101
2102         path = btrfs_alloc_path();
2103         if (!path)
2104                 return -ENOMEM;
2105
2106         path->reada = 2;
2107         path->search_commit_root = 1;
2108         path->skip_locking = 1;
2109
2110         key.objectid = scrub_dev->devid;
2111         key.offset = 0ull;
2112         key.type = BTRFS_DEV_EXTENT_KEY;
2113
2114         while (1) {
2115                 ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
2116                 if (ret < 0)
2117                         break;
2118                 if (ret > 0) {
2119                         if (path->slots[0] >=
2120                             btrfs_header_nritems(path->nodes[0])) {
2121                                 ret = btrfs_next_leaf(root, path);
2122                                 if (ret)
2123                                         break;
2124                         }
2125                 }
2126
2127                 l = path->nodes[0];
2128                 slot = path->slots[0];
2129
2130                 btrfs_item_key_to_cpu(l, &found_key, slot);
2131
2132                 if (found_key.objectid != scrub_dev->devid)
2133                         break;
2134
2135                 if (btrfs_key_type(&found_key) != BTRFS_DEV_EXTENT_KEY)
2136                         break;
2137
2138                 if (found_key.offset >= end)
2139                         break;
2140
2141                 if (found_key.offset < key.offset)
2142                         break;
2143
2144                 dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
2145                 length = btrfs_dev_extent_length(l, dev_extent);
2146
2147                 if (found_key.offset + length <= start) {
2148                         key.offset = found_key.offset + length;
2149                         btrfs_release_path(path);
2150                         continue;
2151                 }
2152
2153                 chunk_tree = btrfs_dev_extent_chunk_tree(l, dev_extent);
2154                 chunk_objectid = btrfs_dev_extent_chunk_objectid(l, dev_extent);
2155                 chunk_offset = btrfs_dev_extent_chunk_offset(l, dev_extent);
2156
2157                 /*
2158                  * get a reference on the corresponding block group to prevent
2159                  * the chunk from going away while we scrub it
2160                  */
2161                 cache = btrfs_lookup_block_group(fs_info, chunk_offset);
2162                 if (!cache) {
2163                         ret = -ENOENT;
2164                         break;
2165                 }
2166                 ret = scrub_chunk(sctx, scrub_dev, chunk_tree, chunk_objectid,
2167                                   chunk_offset, length, found_key.offset);
2168                 btrfs_put_block_group(cache);
2169                 if (ret)
2170                         break;
2171
2172                 key.offset = found_key.offset + length;
2173                 btrfs_release_path(path);
2174         }
2175
2176         btrfs_free_path(path);
2177
2178         /*
2179          * ret can still be 1 from search_slot or next_leaf,
2180          * that's not an error
2181          */
2182         return ret < 0 ? ret : 0;
2183 }
2184
2185 static noinline_for_stack int scrub_supers(struct scrub_ctx *sctx,
2186                                            struct btrfs_device *scrub_dev)
2187 {
2188         int     i;
2189         u64     bytenr;
2190         u64     gen;
2191         int     ret;
2192         struct btrfs_root *root = sctx->dev_root;
2193
2194         if (root->fs_info->fs_state & BTRFS_SUPER_FLAG_ERROR)
2195                 return -EIO;
2196
2197         gen = root->fs_info->last_trans_committed;
2198
2199         for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
2200                 bytenr = btrfs_sb_offset(i);
2201                 if (bytenr + BTRFS_SUPER_INFO_SIZE > scrub_dev->total_bytes)
2202                         break;
2203
2204                 ret = scrub_pages(sctx, bytenr, BTRFS_SUPER_INFO_SIZE, bytenr,
2205                                   scrub_dev, BTRFS_EXTENT_FLAG_SUPER, gen, i,
2206                                   NULL, 1);
2207                 if (ret)
2208                         return ret;
2209         }
2210         wait_event(sctx->list_wait, atomic_read(&sctx->in_flight) == 0);
2211
2212         return 0;
2213 }
2214
2215 /*
2216  * get a reference count on fs_info->scrub_workers. start worker if necessary
2217  */
2218 static noinline_for_stack int scrub_workers_get(struct btrfs_root *root)
2219 {
2220         struct btrfs_fs_info *fs_info = root->fs_info;
2221         int ret = 0;
2222
2223         mutex_lock(&fs_info->scrub_lock);
2224         if (fs_info->scrub_workers_refcnt == 0) {
2225                 btrfs_init_workers(&fs_info->scrub_workers, "scrub",
2226                            fs_info->thread_pool_size, &fs_info->generic_worker);
2227                 fs_info->scrub_workers.idle_thresh = 4;
2228                 ret = btrfs_start_workers(&fs_info->scrub_workers);
2229                 if (ret)
2230                         goto out;
2231         }
2232         ++fs_info->scrub_workers_refcnt;
2233 out:
2234         mutex_unlock(&fs_info->scrub_lock);
2235
2236         return ret;
2237 }
2238
2239 static noinline_for_stack void scrub_workers_put(struct btrfs_root *root)
2240 {
2241         struct btrfs_fs_info *fs_info = root->fs_info;
2242
2243         mutex_lock(&fs_info->scrub_lock);
2244         if (--fs_info->scrub_workers_refcnt == 0)
2245                 btrfs_stop_workers(&fs_info->scrub_workers);
2246         WARN_ON(fs_info->scrub_workers_refcnt < 0);
2247         mutex_unlock(&fs_info->scrub_lock);
2248 }
2249
2250
2251 int btrfs_scrub_dev(struct btrfs_root *root, u64 devid, u64 start, u64 end,
2252                     struct btrfs_scrub_progress *progress, int readonly)
2253 {
2254         struct scrub_ctx *sctx;
2255         struct btrfs_fs_info *fs_info = root->fs_info;
2256         int ret;
2257         struct btrfs_device *dev;
2258
2259         if (btrfs_fs_closing(root->fs_info))
2260                 return -EINVAL;
2261
2262         /*
2263          * check some assumptions
2264          */
2265         if (root->nodesize != root->leafsize) {
2266                 printk(KERN_ERR
2267                        "btrfs_scrub: size assumption nodesize == leafsize (%d == %d) fails\n",
2268                        root->nodesize, root->leafsize);
2269                 return -EINVAL;
2270         }
2271
2272         if (root->nodesize > BTRFS_STRIPE_LEN) {
2273                 /*
2274                  * in this case scrub is unable to calculate the checksum
2275                  * the way scrub is implemented. Do not handle this
2276                  * situation at all because it won't ever happen.
2277                  */
2278                 printk(KERN_ERR
2279                        "btrfs_scrub: size assumption nodesize <= BTRFS_STRIPE_LEN (%d <= %d) fails\n",
2280                        root->nodesize, BTRFS_STRIPE_LEN);
2281                 return -EINVAL;
2282         }
2283
2284         if (root->sectorsize != PAGE_SIZE) {
2285                 /* not supported for data w/o checksums */
2286                 printk(KERN_ERR
2287                        "btrfs_scrub: size assumption sectorsize != PAGE_SIZE (%d != %lld) fails\n",
2288                        root->sectorsize, (unsigned long long)PAGE_SIZE);
2289                 return -EINVAL;
2290         }
2291
2292         ret = scrub_workers_get(root);
2293         if (ret)
2294                 return ret;
2295
2296         mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
2297         dev = btrfs_find_device(root, devid, NULL, NULL);
2298         if (!dev || dev->missing) {
2299                 mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
2300                 scrub_workers_put(root);
2301                 return -ENODEV;
2302         }
2303         mutex_lock(&fs_info->scrub_lock);
2304
2305         if (!dev->in_fs_metadata) {
2306                 mutex_unlock(&fs_info->scrub_lock);
2307                 mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
2308                 scrub_workers_put(root);
2309                 return -ENODEV;
2310         }
2311
2312         if (dev->scrub_device) {
2313                 mutex_unlock(&fs_info->scrub_lock);
2314                 mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
2315                 scrub_workers_put(root);
2316                 return -EINPROGRESS;
2317         }
2318         sctx = scrub_setup_ctx(dev);
2319         if (IS_ERR(sctx)) {
2320                 mutex_unlock(&fs_info->scrub_lock);
2321                 mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
2322                 scrub_workers_put(root);
2323                 return PTR_ERR(sctx);
2324         }
2325         sctx->readonly = readonly;
2326         dev->scrub_device = sctx;
2327
2328         atomic_inc(&fs_info->scrubs_running);
2329         mutex_unlock(&fs_info->scrub_lock);
2330         mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
2331
2332         down_read(&fs_info->scrub_super_lock);
2333         ret = scrub_supers(sctx, dev);
2334         up_read(&fs_info->scrub_super_lock);
2335
2336         if (!ret)
2337                 ret = scrub_enumerate_chunks(sctx, dev, start, end);
2338
2339         wait_event(sctx->list_wait, atomic_read(&sctx->in_flight) == 0);
2340         atomic_dec(&fs_info->scrubs_running);
2341         wake_up(&fs_info->scrub_pause_wait);
2342
2343         wait_event(sctx->list_wait, atomic_read(&sctx->fixup_cnt) == 0);
2344
2345         if (progress)
2346                 memcpy(progress, &sctx->stat, sizeof(*progress));
2347
2348         mutex_lock(&fs_info->scrub_lock);
2349         dev->scrub_device = NULL;
2350         mutex_unlock(&fs_info->scrub_lock);
2351
2352         scrub_free_ctx(sctx);
2353         scrub_workers_put(root);
2354
2355         return ret;
2356 }
2357
2358 void btrfs_scrub_pause(struct btrfs_root *root)
2359 {
2360         struct btrfs_fs_info *fs_info = root->fs_info;
2361
2362         mutex_lock(&fs_info->scrub_lock);
2363         atomic_inc(&fs_info->scrub_pause_req);
2364         while (atomic_read(&fs_info->scrubs_paused) !=
2365                atomic_read(&fs_info->scrubs_running)) {
2366                 mutex_unlock(&fs_info->scrub_lock);
2367                 wait_event(fs_info->scrub_pause_wait,
2368                            atomic_read(&fs_info->scrubs_paused) ==
2369                            atomic_read(&fs_info->scrubs_running));
2370                 mutex_lock(&fs_info->scrub_lock);
2371         }
2372         mutex_unlock(&fs_info->scrub_lock);
2373 }
2374
2375 void btrfs_scrub_continue(struct btrfs_root *root)
2376 {
2377         struct btrfs_fs_info *fs_info = root->fs_info;
2378
2379         atomic_dec(&fs_info->scrub_pause_req);
2380         wake_up(&fs_info->scrub_pause_wait);
2381 }
2382
2383 void btrfs_scrub_pause_super(struct btrfs_root *root)
2384 {
2385         down_write(&root->fs_info->scrub_super_lock);
2386 }
2387
2388 void btrfs_scrub_continue_super(struct btrfs_root *root)
2389 {
2390         up_write(&root->fs_info->scrub_super_lock);
2391 }
2392
2393 int __btrfs_scrub_cancel(struct btrfs_fs_info *fs_info)
2394 {
2395
2396         mutex_lock(&fs_info->scrub_lock);
2397         if (!atomic_read(&fs_info->scrubs_running)) {
2398                 mutex_unlock(&fs_info->scrub_lock);
2399                 return -ENOTCONN;
2400         }
2401
2402         atomic_inc(&fs_info->scrub_cancel_req);
2403         while (atomic_read(&fs_info->scrubs_running)) {
2404                 mutex_unlock(&fs_info->scrub_lock);
2405                 wait_event(fs_info->scrub_pause_wait,
2406                            atomic_read(&fs_info->scrubs_running) == 0);
2407                 mutex_lock(&fs_info->scrub_lock);
2408         }
2409         atomic_dec(&fs_info->scrub_cancel_req);
2410         mutex_unlock(&fs_info->scrub_lock);
2411
2412         return 0;
2413 }
2414
2415 int btrfs_scrub_cancel(struct btrfs_root *root)
2416 {
2417         return __btrfs_scrub_cancel(root->fs_info);
2418 }
2419
2420 int btrfs_scrub_cancel_dev(struct btrfs_root *root, struct btrfs_device *dev)
2421 {
2422         struct btrfs_fs_info *fs_info = root->fs_info;
2423         struct scrub_ctx *sctx;
2424
2425         mutex_lock(&fs_info->scrub_lock);
2426         sctx = dev->scrub_device;
2427         if (!sctx) {
2428                 mutex_unlock(&fs_info->scrub_lock);
2429                 return -ENOTCONN;
2430         }
2431         atomic_inc(&sctx->cancel_req);
2432         while (dev->scrub_device) {
2433                 mutex_unlock(&fs_info->scrub_lock);
2434                 wait_event(fs_info->scrub_pause_wait,
2435                            dev->scrub_device == NULL);
2436                 mutex_lock(&fs_info->scrub_lock);
2437         }
2438         mutex_unlock(&fs_info->scrub_lock);
2439
2440         return 0;
2441 }
2442
2443 int btrfs_scrub_cancel_devid(struct btrfs_root *root, u64 devid)
2444 {
2445         struct btrfs_fs_info *fs_info = root->fs_info;
2446         struct btrfs_device *dev;
2447         int ret;
2448
2449         /*
2450          * we have to hold the device_list_mutex here so the device
2451          * does not go away in cancel_dev. FIXME: find a better solution
2452          */
2453         mutex_lock(&fs_info->fs_devices->device_list_mutex);
2454         dev = btrfs_find_device(root, devid, NULL, NULL);
2455         if (!dev) {
2456                 mutex_unlock(&fs_info->fs_devices->device_list_mutex);
2457                 return -ENODEV;
2458         }
2459         ret = btrfs_scrub_cancel_dev(root, dev);
2460         mutex_unlock(&fs_info->fs_devices->device_list_mutex);
2461
2462         return ret;
2463 }
2464
2465 int btrfs_scrub_progress(struct btrfs_root *root, u64 devid,
2466                          struct btrfs_scrub_progress *progress)
2467 {
2468         struct btrfs_device *dev;
2469         struct scrub_ctx *sctx = NULL;
2470
2471         mutex_lock(&root->fs_info->fs_devices->device_list_mutex);
2472         dev = btrfs_find_device(root, devid, NULL, NULL);
2473         if (dev)
2474                 sctx = dev->scrub_device;
2475         if (sctx)
2476                 memcpy(progress, &sctx->stat, sizeof(*progress));
2477         mutex_unlock(&root->fs_info->fs_devices->device_list_mutex);
2478
2479         return dev ? (sctx ? 0 : -ENOTCONN) : -ENODEV;
2480 }