fs/ext4/fsmap.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2017 Oracle.  All Rights Reserved.
   4  *
   5  * Author: Darrick J. Wong <[email protected]>
   6  */
   7 #include "ext4.h"
   8 #include <linux/fsmap.h>
   9 #include "fsmap.h"
  10 #include "mballoc.h"
  11 #include <linux/sort.h>
  12 #include <linux/list_sort.h>
  13 #include <trace/events/ext4.h>
  14
  15 /* Convert an ext4_fsmap to an fsmap. */
  16 void ext4_fsmap_from_internal(struct super_block *sb, struct fsmap *dest,
  17                               struct ext4_fsmap *src)
  18 {
  19         dest->fmr_device = src->fmr_device;
  20         dest->fmr_flags = src->fmr_flags;
  21         dest->fmr_physical = src->fmr_physical << sb->s_blocksize_bits;
  22         dest->fmr_owner = src->fmr_owner;
  23         dest->fmr_offset = 0;
  24         dest->fmr_length = src->fmr_length << sb->s_blocksize_bits;
  25         dest->fmr_reserved[0] = 0;
  26         dest->fmr_reserved[1] = 0;
  27         dest->fmr_reserved[2] = 0;
  28 }
  29
  30 /* Convert an fsmap to an ext4_fsmap. */
  31 void ext4_fsmap_to_internal(struct super_block *sb, struct ext4_fsmap *dest,
  32                             struct fsmap *src)
  33 {
  34         dest->fmr_device = src->fmr_device;
  35         dest->fmr_flags = src->fmr_flags;
  36         dest->fmr_physical = src->fmr_physical >> sb->s_blocksize_bits;
  37         dest->fmr_owner = src->fmr_owner;
  38         dest->fmr_length = src->fmr_length >> sb->s_blocksize_bits;
  39 }
  40
  41 /* getfsmap query state */
  42 struct ext4_getfsmap_info {
  43         struct ext4_fsmap_head  *gfi_head;
  44         ext4_fsmap_format_t     gfi_formatter;  /* formatting fn */
  45         void                    *gfi_format_arg;/* format buffer */
  46         ext4_fsblk_t            gfi_next_fsblk; /* next fsblock we expect */
  47         u32                     gfi_dev;        /* device id */
  48         ext4_group_t            gfi_agno;       /* bg number, if applicable */
  49         struct ext4_fsmap       gfi_low;        /* low rmap key */
  50         struct ext4_fsmap       gfi_high;       /* high rmap key */
  51         struct ext4_fsmap       gfi_lastfree;   /* free ext at end of last bg */
  52         struct list_head        gfi_meta_list;  /* fixed metadata list */
  53         bool                    gfi_last;       /* last extent? */
  54 };
  55
  56 /* Associate a device with a getfsmap handler. */
  57 struct ext4_getfsmap_dev {
  58         int                     (*gfd_fn)(struct super_block *sb,
  59                                       struct ext4_fsmap *keys,
  60                                       struct ext4_getfsmap_info *info);
  61         u32                     gfd_dev;
  62 };
  63
  64 /* Compare two getfsmap device handlers. */
  65 static int ext4_getfsmap_dev_compare(const void *p1, const void *p2)
  66 {
  67         const struct ext4_getfsmap_dev *d1 = p1;
  68         const struct ext4_getfsmap_dev *d2 = p2;
  69
  70         return d1->gfd_dev - d2->gfd_dev;
  71 }
  72
  73 /* Compare a record against our starting point */
  74 static bool ext4_getfsmap_rec_before_low_key(struct ext4_getfsmap_info *info,
  75                                              struct ext4_fsmap *rec)
  76 {
  77         return rec->fmr_physical < info->gfi_low.fmr_physical;
  78 }
  79
  80 /*
  81  * Format a reverse mapping for getfsmap, having translated rm_startblock
  82  * into the appropriate daddr units.
  83  */
  84 static int ext4_getfsmap_helper(struct super_block *sb,
  85                                 struct ext4_getfsmap_info *info,
  86                                 struct ext4_fsmap *rec)
  87 {
  88         struct ext4_fsmap fmr;
  89         struct ext4_sb_info *sbi = EXT4_SB(sb);
  90         ext4_fsblk_t rec_fsblk = rec->fmr_physical;
  91         ext4_group_t agno;
  92         ext4_grpblk_t cno;
  93         int error;
  94
  95         if (fatal_signal_pending(current))
  96                 return -EINTR;
  97
  98         /*
  99          * Filter out records that start before our startpoint, if the
 100          * caller requested that.
 101          */
 102         if (ext4_getfsmap_rec_before_low_key(info, rec)) {
 103                 rec_fsblk += rec->fmr_length;
 104                 if (info->gfi_next_fsblk < rec_fsblk)
 105                         info->gfi_next_fsblk = rec_fsblk;
 106                 return EXT4_QUERY_RANGE_CONTINUE;
 107         }
 108
 109         /* Are we just counting mappings? */
 110         if (info->gfi_head->fmh_count == 0) {
 111                 if (info->gfi_head->fmh_entries == UINT_MAX)
 112                         return EXT4_QUERY_RANGE_ABORT;
 113
 114                 if (rec_fsblk > info->gfi_next_fsblk)
 115                         info->gfi_head->fmh_entries++;
 116
 117                 if (info->gfi_last)
 118                         return EXT4_QUERY_RANGE_CONTINUE;
 119
 120                 info->gfi_head->fmh_entries++;
 121
 122                 rec_fsblk += rec->fmr_length;
 123                 if (info->gfi_next_fsblk < rec_fsblk)
 124                         info->gfi_next_fsblk = rec_fsblk;
 125                 return EXT4_QUERY_RANGE_CONTINUE;
 126         }
 127
 128         /*
 129          * If the record starts past the last physical block we saw,
 130          * then we've found a gap.  Report the gap as being owned by
 131          * whatever the caller specified is the missing owner.
 132          */
 133         if (rec_fsblk > info->gfi_next_fsblk) {
 134                 if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
 135                         return EXT4_QUERY_RANGE_ABORT;
 136
 137                 ext4_get_group_no_and_offset(sb, info->gfi_next_fsblk,
 138                                 &agno, &cno);
 139                 trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno,
 140                                 EXT4_C2B(sbi, cno),
 141                                 rec_fsblk - info->gfi_next_fsblk,
 142                                 EXT4_FMR_OWN_UNKNOWN);
 143
 144                 fmr.fmr_device = info->gfi_dev;
 145                 fmr.fmr_physical = info->gfi_next_fsblk;
 146                 fmr.fmr_owner = EXT4_FMR_OWN_UNKNOWN;
 147                 fmr.fmr_length = rec_fsblk - info->gfi_next_fsblk;
 148                 fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
 149                 error = info->gfi_formatter(&fmr, info->gfi_format_arg);
 150                 if (error)
 151                         return error;
 152                 info->gfi_head->fmh_entries++;
 153         }
 154
 155         if (info->gfi_last)
 156                 goto out;
 157
 158         /* Fill out the extent we found */
 159         if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
 160                 return EXT4_QUERY_RANGE_ABORT;
 161
 162         ext4_get_group_no_and_offset(sb, rec_fsblk, &agno, &cno);
 163         trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno, EXT4_C2B(sbi, cno),
 164                         rec->fmr_length, rec->fmr_owner);
 165
 166         fmr.fmr_device = info->gfi_dev;
 167         fmr.fmr_physical = rec_fsblk;
 168         fmr.fmr_owner = rec->fmr_owner;
 169         fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
 170         fmr.fmr_length = rec->fmr_length;
 171         error = info->gfi_formatter(&fmr, info->gfi_format_arg);
 172         if (error)
 173                 return error;
 174         info->gfi_head->fmh_entries++;
 175
 176 out:
 177         rec_fsblk += rec->fmr_length;
 178         if (info->gfi_next_fsblk < rec_fsblk)
 179                 info->gfi_next_fsblk = rec_fsblk;
 180         return EXT4_QUERY_RANGE_CONTINUE;
 181 }
 182
 183 static inline ext4_fsblk_t ext4_fsmap_next_pblk(struct ext4_fsmap *fmr)
 184 {
 185         return fmr->fmr_physical + fmr->fmr_length;
 186 }
 187
 188 static int ext4_getfsmap_meta_helper(struct super_block *sb,
 189                                      ext4_group_t agno, ext4_grpblk_t start,
 190                                      ext4_grpblk_t len, void *priv)
 191 {
 192         struct ext4_getfsmap_info *info = priv;
 193         struct ext4_fsmap *p;
 194         struct ext4_fsmap *tmp;
 195         struct ext4_sb_info *sbi = EXT4_SB(sb);
 196         ext4_fsblk_t fsb, fs_start, fs_end;
 197         int error;
 198
 199         fs_start = fsb = (EXT4_C2B(sbi, start) +
 200                           ext4_group_first_block_no(sb, agno));
 201         fs_end = fs_start + EXT4_C2B(sbi, len);
 202
 203         /* Return relevant extents from the meta_list */
 204         list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
 205                 if (p->fmr_physical < info->gfi_next_fsblk) {
 206                         list_del(&p->fmr_list);
 207                         kfree(p);
 208                         continue;
 209                 }
 210                 if (p->fmr_physical <= fs_start ||
 211                     p->fmr_physical + p->fmr_length <= fs_end) {
 212                         /* Emit the retained free extent record if present */
 213                         if (info->gfi_lastfree.fmr_owner) {
 214                                 error = ext4_getfsmap_helper(sb, info,
 215                                                         &info->gfi_lastfree);
 216                                 if (error)
 217                                         return error;
 218                                 info->gfi_lastfree.fmr_owner = 0;
 219                         }
 220                         error = ext4_getfsmap_helper(sb, info, p);
 221                         if (error)
 222                                 return error;
 223                         fsb = p->fmr_physical + p->fmr_length;
 224                         if (info->gfi_next_fsblk < fsb)
 225                                 info->gfi_next_fsblk = fsb;
 226                         list_del(&p->fmr_list);
 227                         kfree(p);
 228                         continue;
 229                 }
 230         }
 231         if (info->gfi_next_fsblk < fsb)
 232                 info->gfi_next_fsblk = fsb;
 233
 234         return 0;
 235 }
 236
 237
 238 /* Transform a blockgroup's free record into a fsmap */
 239 static int ext4_getfsmap_datadev_helper(struct super_block *sb,
 240                                         ext4_group_t agno, ext4_grpblk_t start,
 241                                         ext4_grpblk_t len, void *priv)
 242 {
 243         struct ext4_fsmap irec;
 244         struct ext4_getfsmap_info *info = priv;
 245         struct ext4_fsmap *p;
 246         struct ext4_fsmap *tmp;
 247         struct ext4_sb_info *sbi = EXT4_SB(sb);
 248         ext4_fsblk_t fsb;
 249         ext4_fsblk_t fslen;
 250         int error;
 251
 252         fsb = (EXT4_C2B(sbi, start) + ext4_group_first_block_no(sb, agno));
 253         fslen = EXT4_C2B(sbi, len);
 254
 255         /* If the retained free extent record is set... */
 256         if (info->gfi_lastfree.fmr_owner) {
 257                 /* ...and abuts this one, lengthen it and return. */
 258                 if (ext4_fsmap_next_pblk(&info->gfi_lastfree) == fsb) {
 259                         info->gfi_lastfree.fmr_length += fslen;
 260                         return 0;
 261                 }
 262
 263                 /*
 264                  * There's a gap between the two free extents; emit the
 265                  * retained extent prior to merging the meta_list.
 266                  */
 267                 error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
 268                 if (error)
 269                         return error;
 270                 info->gfi_lastfree.fmr_owner = 0;
 271         }
 272
 273         /* Merge in any relevant extents from the meta_list */
 274         list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
 275                 if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) {
 276                         list_del(&p->fmr_list);
 277                         kfree(p);
 278                 } else if (p->fmr_physical < fsb) {
 279                         error = ext4_getfsmap_helper(sb, info, p);
 280                         if (error)
 281                                 return error;
 282
 283                         list_del(&p->fmr_list);
 284                         kfree(p);
 285                 }
 286         }
 287
 288         irec.fmr_device = 0;
 289         irec.fmr_physical = fsb;
 290         irec.fmr_length = fslen;
 291         irec.fmr_owner = EXT4_FMR_OWN_FREE;
 292         irec.fmr_flags = 0;
 293
 294         /* If this is a free extent at the end of a bg, buffer it. */
 295         if (ext4_fsmap_next_pblk(&irec) ==
 296                         ext4_group_first_block_no(sb, agno + 1)) {
 297                 info->gfi_lastfree = irec;
 298                 return 0;
 299         }
 300
 301         /* Otherwise, emit it */
 302         return ext4_getfsmap_helper(sb, info, &irec);
 303 }
 304
 305 /* Execute a getfsmap query against the log device. */
 306 static int ext4_getfsmap_logdev(struct super_block *sb, struct ext4_fsmap *keys,
 307                                 struct ext4_getfsmap_info *info)
 308 {
 309         journal_t *journal = EXT4_SB(sb)->s_journal;
 310         struct ext4_fsmap irec;
 311
 312         /* Set up search keys */
 313         info->gfi_low = keys[0];
 314         info->gfi_low.fmr_length = 0;
 315
 316         memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
 317
 318         trace_ext4_fsmap_low_key(sb, info->gfi_dev, 0,
 319                         info->gfi_low.fmr_physical,
 320                         info->gfi_low.fmr_length,
 321                         info->gfi_low.fmr_owner);
 322
 323         trace_ext4_fsmap_high_key(sb, info->gfi_dev, 0,
 324                         info->gfi_high.fmr_physical,
 325                         info->gfi_high.fmr_length,
 326                         info->gfi_high.fmr_owner);
 327
 328         if (keys[0].fmr_physical > 0)
 329                 return 0;
 330
 331         /* Fabricate an rmap entry for the external log device. */
 332         irec.fmr_physical = journal->j_blk_offset;
 333         irec.fmr_length = journal->j_total_len;
 334         irec.fmr_owner = EXT4_FMR_OWN_LOG;
 335         irec.fmr_flags = 0;
 336
 337         return ext4_getfsmap_helper(sb, info, &irec);
 338 }
 339
 340 /* Helper to fill out an ext4_fsmap. */
 341 static inline int ext4_getfsmap_fill(struct list_head *meta_list,
 342                                      ext4_fsblk_t fsb, ext4_fsblk_t len,
 343                                      uint64_t owner)
 344 {
 345         struct ext4_fsmap *fsm;
 346
 347         fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
 348         if (!fsm)
 349                 return -ENOMEM;
 350         fsm->fmr_device = 0;
 351         fsm->fmr_flags = 0;
 352         fsm->fmr_physical = fsb;
 353         fsm->fmr_owner = owner;
 354         fsm->fmr_length = len;
 355         list_add_tail(&fsm->fmr_list, meta_list);
 356
 357         return 0;
 358 }
 359
 360 /*
 361  * This function returns the number of file system metadata blocks at
 362  * the beginning of a block group, including the reserved gdt blocks.
 363  */
 364 static unsigned int ext4_getfsmap_find_sb(struct super_block *sb,
 365                                           ext4_group_t agno,
 366                                           struct list_head *meta_list)
 367 {
 368         struct ext4_sb_info *sbi = EXT4_SB(sb);
 369         ext4_fsblk_t fsb = ext4_group_first_block_no(sb, agno);
 370         ext4_fsblk_t len;
 371         unsigned long first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);
 372         unsigned long metagroup = agno / EXT4_DESC_PER_BLOCK(sb);
 373         int error;
 374
 375         /* Record the superblock. */
 376         if (ext4_bg_has_super(sb, agno)) {
 377                 error = ext4_getfsmap_fill(meta_list, fsb, 1, EXT4_FMR_OWN_FS);
 378                 if (error)
 379                         return error;
 380                 fsb++;
 381         }
 382
 383         /* Record the group descriptors. */
 384         len = ext4_bg_num_gdb(sb, agno);
 385         if (!len)
 386                 return 0;
 387         error = ext4_getfsmap_fill(meta_list, fsb, len,
 388                                    EXT4_FMR_OWN_GDT);
 389         if (error)
 390                 return error;
 391         fsb += len;
 392
 393         /* Reserved GDT blocks */
 394         if (!ext4_has_feature_meta_bg(sb) || metagroup < first_meta_bg) {
 395                 len = le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 396                 error = ext4_getfsmap_fill(meta_list, fsb, len,
 397                                            EXT4_FMR_OWN_RESV_GDT);
 398                 if (error)
 399                         return error;
 400         }
 401
 402         return 0;
 403 }
 404
 405 /* Compare two fsmap items. */
 406 static int ext4_getfsmap_compare(void *priv,
 407                                  const struct list_head *a,
 408                                  const struct list_head *b)
 409 {
 410         struct ext4_fsmap *fa;
 411         struct ext4_fsmap *fb;
 412
 413         fa = container_of(a, struct ext4_fsmap, fmr_list);
 414         fb = container_of(b, struct ext4_fsmap, fmr_list);
 415         if (fa->fmr_physical < fb->fmr_physical)
 416                 return -1;
 417         else if (fa->fmr_physical > fb->fmr_physical)
 418                 return 1;
 419         return 0;
 420 }
 421
 422 /* Merge adjacent extents of fixed metadata. */
 423 static void ext4_getfsmap_merge_fixed_metadata(struct list_head *meta_list)
 424 {
 425         struct ext4_fsmap *p;
 426         struct ext4_fsmap *prev = NULL;
 427         struct ext4_fsmap *tmp;
 428
 429         list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
 430                 if (!prev) {
 431                         prev = p;
 432                         continue;
 433                 }
 434
 435                 if (prev->fmr_owner == p->fmr_owner &&
 436                     prev->fmr_physical + prev->fmr_length == p->fmr_physical) {
 437                         prev->fmr_length += p->fmr_length;
 438                         list_del(&p->fmr_list);
 439                         kfree(p);
 440                 } else
 441                         prev = p;
 442         }
 443 }
 444
 445 /* Free a list of fixed metadata. */
 446 static void ext4_getfsmap_free_fixed_metadata(struct list_head *meta_list)
 447 {
 448         struct ext4_fsmap *p;
 449         struct ext4_fsmap *tmp;
 450
 451         list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
 452                 list_del(&p->fmr_list);
 453                 kfree(p);
 454         }
 455 }
 456
 457 /* Find all the fixed metadata in the filesystem. */
 458 static int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
 459                                              struct list_head *meta_list)
 460 {
 461         struct ext4_group_desc *gdp;
 462         ext4_group_t agno;
 463         int error;
 464
 465         INIT_LIST_HEAD(meta_list);
 466
 467         /* Collect everything. */
 468         for (agno = 0; agno < EXT4_SB(sb)->s_groups_count; agno++) {
 469                 gdp = ext4_get_group_desc(sb, agno, NULL);
 470                 if (!gdp) {
 471                         error = -EFSCORRUPTED;
 472                         goto err;
 473                 }
 474
 475                 /* Superblock & GDT */
 476                 error = ext4_getfsmap_find_sb(sb, agno, meta_list);
 477                 if (error)
 478                         goto err;
 479
 480                 /* Block bitmap */
 481                 error = ext4_getfsmap_fill(meta_list,
 482                                            ext4_block_bitmap(sb, gdp), 1,
 483                                            EXT4_FMR_OWN_BLKBM);
 484                 if (error)
 485                         goto err;
 486
 487                 /* Inode bitmap */
 488                 error = ext4_getfsmap_fill(meta_list,
 489                                            ext4_inode_bitmap(sb, gdp), 1,
 490                                            EXT4_FMR_OWN_INOBM);
 491                 if (error)
 492                         goto err;
 493
 494                 /* Inodes */
 495                 error = ext4_getfsmap_fill(meta_list,
 496                                            ext4_inode_table(sb, gdp),
 497                                            EXT4_SB(sb)->s_itb_per_group,
 498                                            EXT4_FMR_OWN_INODES);
 499                 if (error)
 500                         goto err;
 501         }
 502
 503         /* Sort the list */
 504         list_sort(NULL, meta_list, ext4_getfsmap_compare);
 505
 506         /* Merge adjacent extents */
 507         ext4_getfsmap_merge_fixed_metadata(meta_list);
 508
 509         return 0;
 510 err:
 511         ext4_getfsmap_free_fixed_metadata(meta_list);
 512         return error;
 513 }
 514
 515 /* Execute a getfsmap query against the buddy bitmaps */
 516 static int ext4_getfsmap_datadev(struct super_block *sb,
 517                                  struct ext4_fsmap *keys,
 518                                  struct ext4_getfsmap_info *info)
 519 {
 520         struct ext4_sb_info *sbi = EXT4_SB(sb);
 521         ext4_fsblk_t start_fsb;
 522         ext4_fsblk_t end_fsb;
 523         ext4_fsblk_t bofs;
 524         ext4_fsblk_t eofs;
 525         ext4_group_t start_ag;
 526         ext4_group_t end_ag;
 527         ext4_grpblk_t first_cluster;
 528         ext4_grpblk_t last_cluster;
 529         int error = 0;
 530
 531         bofs = le32_to_cpu(sbi->s_es->s_first_data_block);
 532         eofs = ext4_blocks_count(sbi->s_es);
 533         if (keys[0].fmr_physical >= eofs)
 534                 return 0;
 535         else if (keys[0].fmr_physical < bofs)
 536                 keys[0].fmr_physical = bofs;
 537         if (keys[1].fmr_physical >= eofs)
 538                 keys[1].fmr_physical = eofs - 1;
 539         if (keys[1].fmr_physical < keys[0].fmr_physical)
 540                 return 0;
 541         start_fsb = keys[0].fmr_physical;
 542         end_fsb = keys[1].fmr_physical;
 543
 544         /* Determine first and last group to examine based on start and end */
 545         ext4_get_group_no_and_offset(sb, start_fsb, &start_ag, &first_cluster);
 546         ext4_get_group_no_and_offset(sb, end_fsb, &end_ag, &last_cluster);
 547
 548         /*
 549          * Convert the fsmap low/high keys to bg based keys.  Initialize
 550          * low to the fsmap low key and max out the high key to the end
 551          * of the bg.
 552          */
 553         info->gfi_low = keys[0];
 554         info->gfi_low.fmr_physical = EXT4_C2B(sbi, first_cluster);
 555         info->gfi_low.fmr_length = 0;
 556
 557         memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
 558
 559         /* Assemble a list of all the fixed-location metadata. */
 560         error = ext4_getfsmap_find_fixed_metadata(sb, &info->gfi_meta_list);
 561         if (error)
 562                 goto err;
 563
 564         /* Query each bg */
 565         for (info->gfi_agno = start_ag;
 566              info->gfi_agno <= end_ag;
 567              info->gfi_agno++) {
 568                 /*
 569                  * Set the bg high key from the fsmap high key if this
 570                  * is the last bg that we're querying.
 571                  */
 572                 if (info->gfi_agno == end_ag) {
 573                         info->gfi_high = keys[1];
 574                         info->gfi_high.fmr_physical = EXT4_C2B(sbi,
 575                                         last_cluster);
 576                         info->gfi_high.fmr_length = 0;
 577                 }
 578
 579                 trace_ext4_fsmap_low_key(sb, info->gfi_dev, info->gfi_agno,
 580                                 info->gfi_low.fmr_physical,
 581                                 info->gfi_low.fmr_length,
 582                                 info->gfi_low.fmr_owner);
 583
 584                 trace_ext4_fsmap_high_key(sb, info->gfi_dev, info->gfi_agno,
 585                                 info->gfi_high.fmr_physical,
 586                                 info->gfi_high.fmr_length,
 587                                 info->gfi_high.fmr_owner);
 588
 589                 error = ext4_mballoc_query_range(sb, info->gfi_agno,
 590                                 EXT4_B2C(sbi, info->gfi_low.fmr_physical),
 591                                 EXT4_B2C(sbi, info->gfi_high.fmr_physical),
 592                                 ext4_getfsmap_meta_helper,
 593                                 ext4_getfsmap_datadev_helper, info);
 594                 if (error)
 595                         goto err;
 596
 597                 /*
 598                  * Set the bg low key to the start of the bg prior to
 599                  * moving on to the next bg.
 600                  */
 601                 if (info->gfi_agno == start_ag)
 602                         memset(&info->gfi_low, 0, sizeof(info->gfi_low));
 603         }
 604
 605         /* Do we have a retained free extent? */
 606         if (info->gfi_lastfree.fmr_owner) {
 607                 error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
 608                 if (error)
 609                         goto err;
 610         }
 611
 612         /* Report any gaps at the end of the bg */
 613         info->gfi_last = true;
 614         error = ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster + 1,
 615                                              0, info);
 616         if (error)
 617                 goto err;
 618
 619 err:
 620         ext4_getfsmap_free_fixed_metadata(&info->gfi_meta_list);
 621         return error;
 622 }
 623
 624 /* Do we recognize the device? */
 625 static bool ext4_getfsmap_is_valid_device(struct super_block *sb,
 626                                           struct ext4_fsmap *fm)
 627 {
 628         if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
 629             fm->fmr_device == new_encode_dev(sb->s_bdev->bd_dev))
 630                 return true;
 631         if (EXT4_SB(sb)->s_journal_bdev_file &&
 632             fm->fmr_device ==
 633             new_encode_dev(file_bdev(EXT4_SB(sb)->s_journal_bdev_file)->bd_dev))
 634                 return true;
 635         return false;
 636 }
 637
 638 /* Ensure that the low key is less than the high key. */
 639 static bool ext4_getfsmap_check_keys(struct ext4_fsmap *low_key,
 640                                      struct ext4_fsmap *high_key)
 641 {
 642         if (low_key->fmr_device > high_key->fmr_device)
 643                 return false;
 644         if (low_key->fmr_device < high_key->fmr_device)
 645                 return true;
 646
 647         if (low_key->fmr_physical > high_key->fmr_physical)
 648                 return false;
 649         if (low_key->fmr_physical < high_key->fmr_physical)
 650                 return true;
 651
 652         if (low_key->fmr_owner > high_key->fmr_owner)
 653                 return false;
 654         if (low_key->fmr_owner < high_key->fmr_owner)
 655                 return true;
 656
 657         return false;
 658 }
 659
 660 #define EXT4_GETFSMAP_DEVS      2
 661 /*
 662  * Get filesystem's extents as described in head, and format for
 663  * output.  Calls formatter to fill the user's buffer until all
 664  * extents are mapped, until the passed-in head->fmh_count slots have
 665  * been filled, or until the formatter short-circuits the loop, if it
 666  * is tracking filled-in extents on its own.
 667  *
 668  * Key to Confusion
 669  * ----------------
 670  * There are multiple levels of keys and counters at work here:
 671  * _fsmap_head.fmh_keys         -- low and high fsmap keys passed in;
 672  *                                 these reflect fs-wide block addrs.
 673  * dkeys                        -- fmh_keys used to query each device;
 674  *                                 these are fmh_keys but w/ the low key
 675  *                                 bumped up by fmr_length.
 676  * _getfsmap_info.gfi_next_fsblk-- next fs block we expect to see; this
 677  *                                 is how we detect gaps in the fsmap
 678  *                                 records and report them.
 679  * _getfsmap_info.gfi_low/high  -- per-bg low/high keys computed from
 680  *                                 dkeys; used to query the free space.
 681  */
 682 int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
 683                   ext4_fsmap_format_t formatter, void *arg)
 684 {
 685         struct ext4_fsmap dkeys[2];     /* per-dev keys */
 686         struct ext4_getfsmap_dev handlers[EXT4_GETFSMAP_DEVS];
 687         struct ext4_getfsmap_info info = { NULL };
 688         int i;
 689         int error = 0;
 690
 691         if (head->fmh_iflags & ~FMH_IF_VALID)
 692                 return -EINVAL;
 693         if (!ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[0]) ||
 694             !ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[1]))
 695                 return -EINVAL;
 696
 697         head->fmh_entries = 0;
 698
 699         /* Set up our device handlers. */
 700         memset(handlers, 0, sizeof(handlers));
 701         handlers[0].gfd_dev = new_encode_dev(sb->s_bdev->bd_dev);
 702         handlers[0].gfd_fn = ext4_getfsmap_datadev;
 703         if (EXT4_SB(sb)->s_journal_bdev_file) {
 704                 handlers[1].gfd_dev = new_encode_dev(
 705                         file_bdev(EXT4_SB(sb)->s_journal_bdev_file)->bd_dev);
 706                 handlers[1].gfd_fn = ext4_getfsmap_logdev;
 707         }
 708
 709         sort(handlers, EXT4_GETFSMAP_DEVS, sizeof(struct ext4_getfsmap_dev),
 710                         ext4_getfsmap_dev_compare, NULL);
 711
 712         /*
 713          * To continue where we left off, we allow userspace to use the
 714          * last mapping from a previous call as the low key of the next.
 715          * This is identified by a non-zero length in the low key. We
 716          * have to increment the low key in this scenario to ensure we
 717          * don't return the same mapping again, and instead return the
 718          * very next mapping.
 719          *
 720          * Bump the physical offset as there can be no other mapping for
 721          * the same physical block range.
 722          */
 723         dkeys[0] = head->fmh_keys[0];
 724         dkeys[0].fmr_physical += dkeys[0].fmr_length;
 725         dkeys[0].fmr_owner = 0;
 726         dkeys[0].fmr_length = 0;
 727         memset(&dkeys[1], 0xFF, sizeof(struct ext4_fsmap));
 728
 729         if (!ext4_getfsmap_check_keys(dkeys, &head->fmh_keys[1]))
 730                 return -EINVAL;
 731
 732         info.gfi_next_fsblk = head->fmh_keys[0].fmr_physical +
 733                           head->fmh_keys[0].fmr_length;
 734         info.gfi_formatter = formatter;
 735         info.gfi_format_arg = arg;
 736         info.gfi_head = head;
 737
 738         /* For each device we support... */
 739         for (i = 0; i < EXT4_GETFSMAP_DEVS; i++) {
 740                 /* Is this device within the range the user asked for? */
 741                 if (!handlers[i].gfd_fn)
 742                         continue;
 743                 if (head->fmh_keys[0].fmr_device > handlers[i].gfd_dev)
 744                         continue;
 745                 if (head->fmh_keys[1].fmr_device < handlers[i].gfd_dev)
 746                         break;
 747
 748                 /*
 749                  * If this device number matches the high key, we have
 750                  * to pass the high key to the handler to limit the
 751                  * query results.  If the device number exceeds the
 752                  * low key, zero out the low key so that we get
 753                  * everything from the beginning.
 754                  */
 755                 if (handlers[i].gfd_dev == head->fmh_keys[1].fmr_device)
 756                         dkeys[1] = head->fmh_keys[1];
 757                 if (handlers[i].gfd_dev > head->fmh_keys[0].fmr_device)
 758                         memset(&dkeys[0], 0, sizeof(struct ext4_fsmap));
 759
 760                 info.gfi_dev = handlers[i].gfd_dev;
 761                 info.gfi_last = false;
 762                 info.gfi_agno = -1;
 763                 error = handlers[i].gfd_fn(sb, dkeys, &info);
 764                 if (error)
 765                         break;
 766                 info.gfi_next_fsblk = 0;
 767         }
 768
 769         head->fmh_oflags = FMH_OF_DEV_T;
 770         return error;
 771 }