fs/ext4/fsmap.c

   1 /*
   2  * Copyright (C) 2017 Oracle.  All Rights Reserved.
   3  *
   4  * Author: Darrick J. Wong <darrick.wong@oracle.com>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version 2
   9  * of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it would be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write the Free Software Foundation,
  18  * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
  19  */
  20 #include "ext4.h"
  21 #include <linux/fsmap.h>
  22 #include "fsmap.h"
  23 #include "mballoc.h"
  24 #include <linux/sort.h>
  25 #include <linux/list_sort.h>
  26 #include <trace/events/ext4.h>
  27
  28 /* Convert an ext4_fsmap to an fsmap. */
  29 void ext4_fsmap_from_internal(struct super_block *sb, struct fsmap *dest,
  30                               struct ext4_fsmap *src)
  31 {
  32         dest->fmr_device = src->fmr_device;
  33         dest->fmr_flags = src->fmr_flags;
  34         dest->fmr_physical = src->fmr_physical << sb->s_blocksize_bits;
  35         dest->fmr_owner = src->fmr_owner;
  36         dest->fmr_offset = 0;
  37         dest->fmr_length = src->fmr_length << sb->s_blocksize_bits;
  38         dest->fmr_reserved[0] = 0;
  39         dest->fmr_reserved[1] = 0;
  40         dest->fmr_reserved[2] = 0;
  41 }
  42
  43 /* Convert an fsmap to an ext4_fsmap. */
  44 void ext4_fsmap_to_internal(struct super_block *sb, struct ext4_fsmap *dest,
  45                             struct fsmap *src)
  46 {
  47         dest->fmr_device = src->fmr_device;
  48         dest->fmr_flags = src->fmr_flags;
  49         dest->fmr_physical = src->fmr_physical >> sb->s_blocksize_bits;
  50         dest->fmr_owner = src->fmr_owner;
  51         dest->fmr_length = src->fmr_length >> sb->s_blocksize_bits;
  52 }
  53
  54 /* getfsmap query state */
  55 struct ext4_getfsmap_info {
  56         struct ext4_fsmap_head  *gfi_head;
  57         ext4_fsmap_format_t     gfi_formatter;  /* formatting fn */
  58         void                    *gfi_format_arg;/* format buffer */
  59         ext4_fsblk_t            gfi_next_fsblk; /* next fsblock we expect */
  60         u32                     gfi_dev;        /* device id */
  61         ext4_group_t            gfi_agno;       /* bg number, if applicable */
  62         struct ext4_fsmap       gfi_low;        /* low rmap key */
  63         struct ext4_fsmap       gfi_high;       /* high rmap key */
  64         struct ext4_fsmap       gfi_lastfree;   /* free ext at end of last bg */
  65         struct list_head        gfi_meta_list;  /* fixed metadata list */
  66         bool                    gfi_last;       /* last extent? */
  67 };
  68
  69 /* Associate a device with a getfsmap handler. */
  70 struct ext4_getfsmap_dev {
  71         int                     (*gfd_fn)(struct super_block *sb,
  72                                       struct ext4_fsmap *keys,
  73                                       struct ext4_getfsmap_info *info);
  74         u32                     gfd_dev;
  75 };
  76
  77 /* Compare two getfsmap device handlers. */
  78 static int ext4_getfsmap_dev_compare(const void *p1, const void *p2)
  79 {
  80         const struct ext4_getfsmap_dev *d1 = p1;
  81         const struct ext4_getfsmap_dev *d2 = p2;
  82
  83         return d1->gfd_dev - d2->gfd_dev;
  84 }
  85
  86 /* Compare a record against our starting point */
  87 static bool ext4_getfsmap_rec_before_low_key(struct ext4_getfsmap_info *info,
  88                                              struct ext4_fsmap *rec)
  89 {
  90         return rec->fmr_physical < info->gfi_low.fmr_physical;
  91 }
  92
  93 /*
  94  * Format a reverse mapping for getfsmap, having translated rm_startblock
  95  * into the appropriate daddr units.
  96  */
  97 static int ext4_getfsmap_helper(struct super_block *sb,
  98                                 struct ext4_getfsmap_info *info,
  99                                 struct ext4_fsmap *rec)
 100 {
 101         struct ext4_fsmap fmr;
 102         struct ext4_sb_info *sbi = EXT4_SB(sb);
 103         ext4_fsblk_t rec_fsblk = rec->fmr_physical;
 104         ext4_group_t agno;
 105         ext4_grpblk_t cno;
 106         int error;
 107
 108         if (fatal_signal_pending(current))
 109                 return -EINTR;
 110
 111         /*
 112          * Filter out records that start before our startpoint, if the
 113          * caller requested that.
 114          */
 115         if (ext4_getfsmap_rec_before_low_key(info, rec)) {
 116                 rec_fsblk += rec->fmr_length;
 117                 if (info->gfi_next_fsblk < rec_fsblk)
 118                         info->gfi_next_fsblk = rec_fsblk;
 119                 return EXT4_QUERY_RANGE_CONTINUE;
 120         }
 121
 122         /* Are we just counting mappings? */
 123         if (info->gfi_head->fmh_count == 0) {
 124                 if (rec_fsblk > info->gfi_next_fsblk)
 125                         info->gfi_head->fmh_entries++;
 126
 127                 if (info->gfi_last)
 128                         return EXT4_QUERY_RANGE_CONTINUE;
 129
 130                 info->gfi_head->fmh_entries++;
 131
 132                 rec_fsblk += rec->fmr_length;
 133                 if (info->gfi_next_fsblk < rec_fsblk)
 134                         info->gfi_next_fsblk = rec_fsblk;
 135                 return EXT4_QUERY_RANGE_CONTINUE;
 136         }
 137
 138         /*
 139          * If the record starts past the last physical block we saw,
 140          * then we've found a gap.  Report the gap as being owned by
 141          * whatever the caller specified is the missing owner.
 142          */
 143         if (rec_fsblk > info->gfi_next_fsblk) {
 144                 if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
 145                         return EXT4_QUERY_RANGE_ABORT;
 146
 147                 ext4_get_group_no_and_offset(sb, info->gfi_next_fsblk,
 148                                 &agno, &cno);
 149                 trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno,
 150                                 EXT4_C2B(sbi, cno),
 151                                 rec_fsblk - info->gfi_next_fsblk,
 152                                 EXT4_FMR_OWN_UNKNOWN);
 153
 154                 fmr.fmr_device = info->gfi_dev;
 155                 fmr.fmr_physical = info->gfi_next_fsblk;
 156                 fmr.fmr_owner = EXT4_FMR_OWN_UNKNOWN;
 157                 fmr.fmr_length = rec_fsblk - info->gfi_next_fsblk;
 158                 fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
 159                 error = info->gfi_formatter(&fmr, info->gfi_format_arg);
 160                 if (error)
 161                         return error;
 162                 info->gfi_head->fmh_entries++;
 163         }
 164
 165         if (info->gfi_last)
 166                 goto out;
 167
 168         /* Fill out the extent we found */
 169         if (info->gfi_head->fmh_entries >= info->gfi_head->fmh_count)
 170                 return EXT4_QUERY_RANGE_ABORT;
 171
 172         ext4_get_group_no_and_offset(sb, rec_fsblk, &agno, &cno);
 173         trace_ext4_fsmap_mapping(sb, info->gfi_dev, agno, EXT4_C2B(sbi, cno),
 174                         rec->fmr_length, rec->fmr_owner);
 175
 176         fmr.fmr_device = info->gfi_dev;
 177         fmr.fmr_physical = rec_fsblk;
 178         fmr.fmr_owner = rec->fmr_owner;
 179         fmr.fmr_flags = FMR_OF_SPECIAL_OWNER;
 180         fmr.fmr_length = rec->fmr_length;
 181         error = info->gfi_formatter(&fmr, info->gfi_format_arg);
 182         if (error)
 183                 return error;
 184         info->gfi_head->fmh_entries++;
 185
 186 out:
 187         rec_fsblk += rec->fmr_length;
 188         if (info->gfi_next_fsblk < rec_fsblk)
 189                 info->gfi_next_fsblk = rec_fsblk;
 190         return EXT4_QUERY_RANGE_CONTINUE;
 191 }
 192
 193 static inline ext4_fsblk_t ext4_fsmap_next_pblk(struct ext4_fsmap *fmr)
 194 {
 195         return fmr->fmr_physical + fmr->fmr_length;
 196 }
 197
 198 /* Transform a blockgroup's free record into a fsmap */
 199 static int ext4_getfsmap_datadev_helper(struct super_block *sb,
 200                                         ext4_group_t agno, ext4_grpblk_t start,
 201                                         ext4_grpblk_t len, void *priv)
 202 {
 203         struct ext4_fsmap irec;
 204         struct ext4_getfsmap_info *info = priv;
 205         struct ext4_fsmap *p;
 206         struct ext4_fsmap *tmp;
 207         struct ext4_sb_info *sbi = EXT4_SB(sb);
 208         ext4_fsblk_t fsb;
 209         ext4_fsblk_t fslen;
 210         int error;
 211
 212         fsb = (EXT4_C2B(sbi, start) + ext4_group_first_block_no(sb, agno));
 213         fslen = EXT4_C2B(sbi, len);
 214
 215         /* If the retained free extent record is set... */
 216         if (info->gfi_lastfree.fmr_owner) {
 217                 /* ...and abuts this one, lengthen it and return. */
 218                 if (ext4_fsmap_next_pblk(&info->gfi_lastfree) == fsb) {
 219                         info->gfi_lastfree.fmr_length += fslen;
 220                         return 0;
 221                 }
 222
 223                 /*
 224                  * There's a gap between the two free extents; emit the
 225                  * retained extent prior to merging the meta_list.
 226                  */
 227                 error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
 228                 if (error)
 229                         return error;
 230                 info->gfi_lastfree.fmr_owner = 0;
 231         }
 232
 233         /* Merge in any relevant extents from the meta_list */
 234         list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
 235                 if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) {
 236                         list_del(&p->fmr_list);
 237                         kfree(p);
 238                 } else if (p->fmr_physical < fsb) {
 239                         error = ext4_getfsmap_helper(sb, info, p);
 240                         if (error)
 241                                 return error;
 242
 243                         list_del(&p->fmr_list);
 244                         kfree(p);
 245                 }
 246         }
 247
 248         irec.fmr_device = 0;
 249         irec.fmr_physical = fsb;
 250         irec.fmr_length = fslen;
 251         irec.fmr_owner = EXT4_FMR_OWN_FREE;
 252         irec.fmr_flags = 0;
 253
 254         /* If this is a free extent at the end of a bg, buffer it. */
 255         if (ext4_fsmap_next_pblk(&irec) ==
 256                         ext4_group_first_block_no(sb, agno + 1)) {
 257                 info->gfi_lastfree = irec;
 258                 return 0;
 259         }
 260
 261         /* Otherwise, emit it */
 262         return ext4_getfsmap_helper(sb, info, &irec);
 263 }
 264
 265 /* Execute a getfsmap query against the log device. */
 266 static int ext4_getfsmap_logdev(struct super_block *sb, struct ext4_fsmap *keys,
 267                                 struct ext4_getfsmap_info *info)
 268 {
 269         journal_t *journal = EXT4_SB(sb)->s_journal;
 270         struct ext4_fsmap irec;
 271
 272         /* Set up search keys */
 273         info->gfi_low = keys[0];
 274         info->gfi_low.fmr_length = 0;
 275
 276         memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
 277
 278         trace_ext4_fsmap_low_key(sb, info->gfi_dev, 0,
 279                         info->gfi_low.fmr_physical,
 280                         info->gfi_low.fmr_length,
 281                         info->gfi_low.fmr_owner);
 282
 283         trace_ext4_fsmap_high_key(sb, info->gfi_dev, 0,
 284                         info->gfi_high.fmr_physical,
 285                         info->gfi_high.fmr_length,
 286                         info->gfi_high.fmr_owner);
 287
 288         if (keys[0].fmr_physical > 0)
 289                 return 0;
 290
 291         /* Fabricate an rmap entry for the external log device. */
 292         irec.fmr_physical = journal->j_blk_offset;
 293         irec.fmr_length = journal->j_maxlen;
 294         irec.fmr_owner = EXT4_FMR_OWN_LOG;
 295         irec.fmr_flags = 0;
 296
 297         return ext4_getfsmap_helper(sb, info, &irec);
 298 }
 299
 300 /* Helper to fill out an ext4_fsmap. */
 301 static inline int ext4_getfsmap_fill(struct list_head *meta_list,
 302                                      ext4_fsblk_t fsb, ext4_fsblk_t len,
 303                                      uint64_t owner)
 304 {
 305         struct ext4_fsmap *fsm;
 306
 307         fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
 308         if (!fsm)
 309                 return -ENOMEM;
 310         fsm->fmr_device = 0;
 311         fsm->fmr_flags = 0;
 312         fsm->fmr_physical = fsb;
 313         fsm->fmr_owner = owner;
 314         fsm->fmr_length = len;
 315         list_add_tail(&fsm->fmr_list, meta_list);
 316
 317         return 0;
 318 }
 319
 320 /*
 321  * This function returns the number of file system metadata blocks at
 322  * the beginning of a block group, including the reserved gdt blocks.
 323  */
 324 static unsigned int ext4_getfsmap_find_sb(struct super_block *sb,
 325                                           ext4_group_t agno,
 326                                           struct list_head *meta_list)
 327 {
 328         struct ext4_sb_info *sbi = EXT4_SB(sb);
 329         ext4_fsblk_t fsb = ext4_group_first_block_no(sb, agno);
 330         ext4_fsblk_t len;
 331         unsigned long first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);
 332         unsigned long metagroup = agno / EXT4_DESC_PER_BLOCK(sb);
 333         int error;
 334
 335         /* Record the superblock. */
 336         if (ext4_bg_has_super(sb, agno)) {
 337                 error = ext4_getfsmap_fill(meta_list, fsb, 1, EXT4_FMR_OWN_FS);
 338                 if (error)
 339                         return error;
 340                 fsb++;
 341         }
 342
 343         /* Record the group descriptors. */
 344         len = ext4_bg_num_gdb(sb, agno);
 345         if (!len)
 346                 return 0;
 347         error = ext4_getfsmap_fill(meta_list, fsb, len,
 348                                    EXT4_FMR_OWN_GDT);
 349         if (error)
 350                 return error;
 351         fsb += len;
 352
 353         /* Reserved GDT blocks */
 354         if (!ext4_has_feature_meta_bg(sb) || metagroup < first_meta_bg) {
 355                 len = le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 356                 error = ext4_getfsmap_fill(meta_list, fsb, len,
 357                                            EXT4_FMR_OWN_RESV_GDT);
 358                 if (error)
 359                         return error;
 360         }
 361
 362         return 0;
 363 }
 364
 365 /* Compare two fsmap items. */
 366 static int ext4_getfsmap_compare(void *priv,
 367                                  struct list_head *a,
 368                                  struct list_head *b)
 369 {
 370         struct ext4_fsmap *fa;
 371         struct ext4_fsmap *fb;
 372
 373         fa = container_of(a, struct ext4_fsmap, fmr_list);
 374         fb = container_of(b, struct ext4_fsmap, fmr_list);
 375         if (fa->fmr_physical < fb->fmr_physical)
 376                 return -1;
 377         else if (fa->fmr_physical > fb->fmr_physical)
 378                 return 1;
 379         return 0;
 380 }
 381
 382 /* Merge adjacent extents of fixed metadata. */
 383 static void ext4_getfsmap_merge_fixed_metadata(struct list_head *meta_list)
 384 {
 385         struct ext4_fsmap *p;
 386         struct ext4_fsmap *prev = NULL;
 387         struct ext4_fsmap *tmp;
 388
 389         list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
 390                 if (!prev) {
 391                         prev = p;
 392                         continue;
 393                 }
 394
 395                 if (prev->fmr_owner == p->fmr_owner &&
 396                     prev->fmr_physical + prev->fmr_length == p->fmr_physical) {
 397                         prev->fmr_length += p->fmr_length;
 398                         list_del(&p->fmr_list);
 399                         kfree(p);
 400                 } else
 401                         prev = p;
 402         }
 403 }
 404
 405 /* Free a list of fixed metadata. */
 406 static void ext4_getfsmap_free_fixed_metadata(struct list_head *meta_list)
 407 {
 408         struct ext4_fsmap *p;
 409         struct ext4_fsmap *tmp;
 410
 411         list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
 412                 list_del(&p->fmr_list);
 413                 kfree(p);
 414         }
 415 }
 416
 417 /* Find all the fixed metadata in the filesystem. */
 418 int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
 419                                       struct list_head *meta_list)
 420 {
 421         struct ext4_group_desc *gdp;
 422         ext4_group_t agno;
 423         int error;
 424
 425         INIT_LIST_HEAD(meta_list);
 426
 427         /* Collect everything. */
 428         for (agno = 0; agno < EXT4_SB(sb)->s_groups_count; agno++) {
 429                 gdp = ext4_get_group_desc(sb, agno, NULL);
 430                 if (!gdp) {
 431                         error = -EFSCORRUPTED;
 432                         goto err;
 433                 }
 434
 435                 /* Superblock & GDT */
 436                 error = ext4_getfsmap_find_sb(sb, agno, meta_list);
 437                 if (error)
 438                         goto err;
 439
 440                 /* Block bitmap */
 441                 error = ext4_getfsmap_fill(meta_list,
 442                                            ext4_block_bitmap(sb, gdp), 1,
 443                                            EXT4_FMR_OWN_BLKBM);
 444                 if (error)
 445                         goto err;
 446
 447                 /* Inode bitmap */
 448                 error = ext4_getfsmap_fill(meta_list,
 449                                            ext4_inode_bitmap(sb, gdp), 1,
 450                                            EXT4_FMR_OWN_INOBM);
 451                 if (error)
 452                         goto err;
 453
 454                 /* Inodes */
 455                 error = ext4_getfsmap_fill(meta_list,
 456                                            ext4_inode_table(sb, gdp),
 457                                            EXT4_SB(sb)->s_itb_per_group,
 458                                            EXT4_FMR_OWN_INODES);
 459                 if (error)
 460                         goto err;
 461         }
 462
 463         /* Sort the list */
 464         list_sort(NULL, meta_list, ext4_getfsmap_compare);
 465
 466         /* Merge adjacent extents */
 467         ext4_getfsmap_merge_fixed_metadata(meta_list);
 468
 469         return 0;
 470 err:
 471         ext4_getfsmap_free_fixed_metadata(meta_list);
 472         return error;
 473 }
 474
 475 /* Execute a getfsmap query against the buddy bitmaps */
 476 static int ext4_getfsmap_datadev(struct super_block *sb,
 477                                  struct ext4_fsmap *keys,
 478                                  struct ext4_getfsmap_info *info)
 479 {
 480         struct ext4_sb_info *sbi = EXT4_SB(sb);
 481         ext4_fsblk_t start_fsb;
 482         ext4_fsblk_t end_fsb;
 483         ext4_fsblk_t eofs;
 484         ext4_group_t start_ag;
 485         ext4_group_t end_ag;
 486         ext4_grpblk_t first_cluster;
 487         ext4_grpblk_t last_cluster;
 488         int error = 0;
 489
 490         eofs = ext4_blocks_count(sbi->s_es);
 491         if (keys[0].fmr_physical >= eofs)
 492                 return 0;
 493         if (keys[1].fmr_physical >= eofs)
 494                 keys[1].fmr_physical = eofs - 1;
 495         start_fsb = keys[0].fmr_physical;
 496         end_fsb = keys[1].fmr_physical;
 497
 498         /* Determine first and last group to examine based on start and end */
 499         ext4_get_group_no_and_offset(sb, start_fsb, &start_ag, &first_cluster);
 500         ext4_get_group_no_and_offset(sb, end_fsb, &end_ag, &last_cluster);
 501
 502         /*
 503          * Convert the fsmap low/high keys to bg based keys.  Initialize
 504          * low to the fsmap low key and max out the high key to the end
 505          * of the bg.
 506          */
 507         info->gfi_low = keys[0];
 508         info->gfi_low.fmr_physical = EXT4_C2B(sbi, first_cluster);
 509         info->gfi_low.fmr_length = 0;
 510
 511         memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
 512
 513         /* Assemble a list of all the fixed-location metadata. */
 514         error = ext4_getfsmap_find_fixed_metadata(sb, &info->gfi_meta_list);
 515         if (error)
 516                 goto err;
 517
 518         /* Query each bg */
 519         for (info->gfi_agno = start_ag;
 520              info->gfi_agno <= end_ag;
 521              info->gfi_agno++) {
 522                 /*
 523                  * Set the bg high key from the fsmap high key if this
 524                  * is the last bg that we're querying.
 525                  */
 526                 if (info->gfi_agno == end_ag) {
 527                         info->gfi_high = keys[1];
 528                         info->gfi_high.fmr_physical = EXT4_C2B(sbi,
 529                                         last_cluster);
 530                         info->gfi_high.fmr_length = 0;
 531                 }
 532
 533                 trace_ext4_fsmap_low_key(sb, info->gfi_dev, info->gfi_agno,
 534                                 info->gfi_low.fmr_physical,
 535                                 info->gfi_low.fmr_length,
 536                                 info->gfi_low.fmr_owner);
 537
 538                 trace_ext4_fsmap_high_key(sb, info->gfi_dev, info->gfi_agno,
 539                                 info->gfi_high.fmr_physical,
 540                                 info->gfi_high.fmr_length,
 541                                 info->gfi_high.fmr_owner);
 542
 543                 error = ext4_mballoc_query_range(sb, info->gfi_agno,
 544                                 EXT4_B2C(sbi, info->gfi_low.fmr_physical),
 545                                 EXT4_B2C(sbi, info->gfi_high.fmr_physical),
 546                                 ext4_getfsmap_datadev_helper, info);
 547                 if (error)
 548                         goto err;
 549
 550                 /*
 551                  * Set the bg low key to the start of the bg prior to
 552                  * moving on to the next bg.
 553                  */
 554                 if (info->gfi_agno == start_ag)
 555                         memset(&info->gfi_low, 0, sizeof(info->gfi_low));
 556         }
 557
 558         /* Do we have a retained free extent? */
 559         if (info->gfi_lastfree.fmr_owner) {
 560                 error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
 561                 if (error)
 562                         goto err;
 563         }
 564
 565         /* Report any gaps at the end of the bg */
 566         info->gfi_last = true;
 567         error = ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster, 0, info);
 568         if (error)
 569                 goto err;
 570
 571 err:
 572         ext4_getfsmap_free_fixed_metadata(&info->gfi_meta_list);
 573         return error;
 574 }
 575
 576 /* Do we recognize the device? */
 577 static bool ext4_getfsmap_is_valid_device(struct super_block *sb,
 578                                           struct ext4_fsmap *fm)
 579 {
 580         if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
 581             fm->fmr_device == new_encode_dev(sb->s_bdev->bd_dev))
 582                 return true;
 583         if (EXT4_SB(sb)->journal_bdev &&
 584             fm->fmr_device == new_encode_dev(EXT4_SB(sb)->journal_bdev->bd_dev))
 585                 return true;
 586         return false;
 587 }
 588
 589 /* Ensure that the low key is less than the high key. */
 590 static bool ext4_getfsmap_check_keys(struct ext4_fsmap *low_key,
 591                                      struct ext4_fsmap *high_key)
 592 {
 593         if (low_key->fmr_device > high_key->fmr_device)
 594                 return false;
 595         if (low_key->fmr_device < high_key->fmr_device)
 596                 return true;
 597
 598         if (low_key->fmr_physical > high_key->fmr_physical)
 599                 return false;
 600         if (low_key->fmr_physical < high_key->fmr_physical)
 601                 return true;
 602
 603         if (low_key->fmr_owner > high_key->fmr_owner)
 604                 return false;
 605         if (low_key->fmr_owner < high_key->fmr_owner)
 606                 return true;
 607
 608         return false;
 609 }
 610
 611 #define EXT4_GETFSMAP_DEVS      2
 612 /*
 613  * Get filesystem's extents as described in head, and format for
 614  * output.  Calls formatter to fill the user's buffer until all
 615  * extents are mapped, until the passed-in head->fmh_count slots have
 616  * been filled, or until the formatter short-circuits the loop, if it
 617  * is tracking filled-in extents on its own.
 618  *
 619  * Key to Confusion
 620  * ----------------
 621  * There are multiple levels of keys and counters at work here:
 622  * _fsmap_head.fmh_keys         -- low and high fsmap keys passed in;
 623  *                                 these reflect fs-wide block addrs.
 624  * dkeys                        -- fmh_keys used to query each device;
 625  *                                 these are fmh_keys but w/ the low key
 626  *                                 bumped up by fmr_length.
 627  * _getfsmap_info.gfi_next_fsblk-- next fs block we expect to see; this
 628  *                                 is how we detect gaps in the fsmap
 629  *                                 records and report them.
 630  * _getfsmap_info.gfi_low/high  -- per-bg low/high keys computed from
 631  *                                 dkeys; used to query the free space.
 632  */
 633 int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
 634                   ext4_fsmap_format_t formatter, void *arg)
 635 {
 636         struct ext4_fsmap dkeys[2];     /* per-dev keys */
 637         struct ext4_getfsmap_dev handlers[EXT4_GETFSMAP_DEVS];
 638         struct ext4_getfsmap_info info = {0};
 639         int i;
 640         int error = 0;
 641
 642         if (head->fmh_iflags & ~FMH_IF_VALID)
 643                 return -EINVAL;
 644         if (!ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[0]) ||
 645             !ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[1]))
 646                 return -EINVAL;
 647
 648         head->fmh_entries = 0;
 649
 650         /* Set up our device handlers. */
 651         memset(handlers, 0, sizeof(handlers));
 652         handlers[0].gfd_dev = new_encode_dev(sb->s_bdev->bd_dev);
 653         handlers[0].gfd_fn = ext4_getfsmap_datadev;
 654         if (EXT4_SB(sb)->journal_bdev) {
 655                 handlers[1].gfd_dev = new_encode_dev(
 656                                 EXT4_SB(sb)->journal_bdev->bd_dev);
 657                 handlers[1].gfd_fn = ext4_getfsmap_logdev;
 658         }
 659
 660         sort(handlers, EXT4_GETFSMAP_DEVS, sizeof(struct ext4_getfsmap_dev),
 661                         ext4_getfsmap_dev_compare, NULL);
 662
 663         /*
 664          * To continue where we left off, we allow userspace to use the
 665          * last mapping from a previous call as the low key of the next.
 666          * This is identified by a non-zero length in the low key. We
 667          * have to increment the low key in this scenario to ensure we
 668          * don't return the same mapping again, and instead return the
 669          * very next mapping.
 670          *
 671          * Bump the physical offset as there can be no other mapping for
 672          * the same physical block range.
 673          */
 674         dkeys[0] = head->fmh_keys[0];
 675         dkeys[0].fmr_physical += dkeys[0].fmr_length;
 676         dkeys[0].fmr_owner = 0;
 677         dkeys[0].fmr_length = 0;
 678         memset(&dkeys[1], 0xFF, sizeof(struct ext4_fsmap));
 679
 680         if (!ext4_getfsmap_check_keys(dkeys, &head->fmh_keys[1]))
 681                 return -EINVAL;
 682
 683         info.gfi_next_fsblk = head->fmh_keys[0].fmr_physical +
 684                           head->fmh_keys[0].fmr_length;
 685         info.gfi_formatter = formatter;
 686         info.gfi_format_arg = arg;
 687         info.gfi_head = head;
 688
 689         /* For each device we support... */
 690         for (i = 0; i < EXT4_GETFSMAP_DEVS; i++) {
 691                 /* Is this device within the range the user asked for? */
 692                 if (!handlers[i].gfd_fn)
 693                         continue;
 694                 if (head->fmh_keys[0].fmr_device > handlers[i].gfd_dev)
 695                         continue;
 696                 if (head->fmh_keys[1].fmr_device < handlers[i].gfd_dev)
 697                         break;
 698
 699                 /*
 700                  * If this device number matches the high key, we have
 701                  * to pass the high key to the handler to limit the
 702                  * query results.  If the device number exceeds the
 703                  * low key, zero out the low key so that we get
 704                  * everything from the beginning.
 705                  */
 706                 if (handlers[i].gfd_dev == head->fmh_keys[1].fmr_device)
 707                         dkeys[1] = head->fmh_keys[1];
 708                 if (handlers[i].gfd_dev > head->fmh_keys[0].fmr_device)
 709                         memset(&dkeys[0], 0, sizeof(struct ext4_fsmap));
 710
 711                 info.gfi_dev = handlers[i].gfd_dev;
 712                 info.gfi_last = false;
 713                 info.gfi_agno = -1;
 714                 error = handlers[i].gfd_fn(sb, dkeys, &info);
 715                 if (error)
 716                         break;
 717                 info.gfi_next_fsblk = 0;
 718         }
 719
 720         head->fmh_oflags = FMH_OF_DEV_T;
 721         return error;
 722 }