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