linux/fs/ext4/fsmap.c
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   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. */
  16void 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. */
  31void 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 */
  42struct 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. */
  57struct 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. */
  65static 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 */
  74static 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 */
  84static 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
 176out:
 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
 183static inline ext4_fsblk_t ext4_fsmap_next_pblk(struct ext4_fsmap *fmr)
 184{
 185        return fmr->fmr_physical + fmr->fmr_length;
 186}
 187
 188/* Transform a blockgroup's free record into a fsmap */
 189static int ext4_getfsmap_datadev_helper(struct super_block *sb,
 190                                        ext4_group_t agno, ext4_grpblk_t start,
 191                                        ext4_grpblk_t len, void *priv)
 192{
 193        struct ext4_fsmap irec;
 194        struct ext4_getfsmap_info *info = priv;
 195        struct ext4_fsmap *p;
 196        struct ext4_fsmap *tmp;
 197        struct ext4_sb_info *sbi = EXT4_SB(sb);
 198        ext4_fsblk_t fsb;
 199        ext4_fsblk_t fslen;
 200        int error;
 201
 202        fsb = (EXT4_C2B(sbi, start) + ext4_group_first_block_no(sb, agno));
 203        fslen = EXT4_C2B(sbi, len);
 204
 205        /* If the retained free extent record is set... */
 206        if (info->gfi_lastfree.fmr_owner) {
 207                /* ...and abuts this one, lengthen it and return. */
 208                if (ext4_fsmap_next_pblk(&info->gfi_lastfree) == fsb) {
 209                        info->gfi_lastfree.fmr_length += fslen;
 210                        return 0;
 211                }
 212
 213                /*
 214                 * There's a gap between the two free extents; emit the
 215                 * retained extent prior to merging the meta_list.
 216                 */
 217                error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
 218                if (error)
 219                        return error;
 220                info->gfi_lastfree.fmr_owner = 0;
 221        }
 222
 223        /* Merge in any relevant extents from the meta_list */
 224        list_for_each_entry_safe(p, tmp, &info->gfi_meta_list, fmr_list) {
 225                if (p->fmr_physical + p->fmr_length <= info->gfi_next_fsblk) {
 226                        list_del(&p->fmr_list);
 227                        kfree(p);
 228                } else if (p->fmr_physical < fsb) {
 229                        error = ext4_getfsmap_helper(sb, info, p);
 230                        if (error)
 231                                return error;
 232
 233                        list_del(&p->fmr_list);
 234                        kfree(p);
 235                }
 236        }
 237
 238        irec.fmr_device = 0;
 239        irec.fmr_physical = fsb;
 240        irec.fmr_length = fslen;
 241        irec.fmr_owner = EXT4_FMR_OWN_FREE;
 242        irec.fmr_flags = 0;
 243
 244        /* If this is a free extent at the end of a bg, buffer it. */
 245        if (ext4_fsmap_next_pblk(&irec) ==
 246                        ext4_group_first_block_no(sb, agno + 1)) {
 247                info->gfi_lastfree = irec;
 248                return 0;
 249        }
 250
 251        /* Otherwise, emit it */
 252        return ext4_getfsmap_helper(sb, info, &irec);
 253}
 254
 255/* Execute a getfsmap query against the log device. */
 256static int ext4_getfsmap_logdev(struct super_block *sb, struct ext4_fsmap *keys,
 257                                struct ext4_getfsmap_info *info)
 258{
 259        journal_t *journal = EXT4_SB(sb)->s_journal;
 260        struct ext4_fsmap irec;
 261
 262        /* Set up search keys */
 263        info->gfi_low = keys[0];
 264        info->gfi_low.fmr_length = 0;
 265
 266        memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
 267
 268        trace_ext4_fsmap_low_key(sb, info->gfi_dev, 0,
 269                        info->gfi_low.fmr_physical,
 270                        info->gfi_low.fmr_length,
 271                        info->gfi_low.fmr_owner);
 272
 273        trace_ext4_fsmap_high_key(sb, info->gfi_dev, 0,
 274                        info->gfi_high.fmr_physical,
 275                        info->gfi_high.fmr_length,
 276                        info->gfi_high.fmr_owner);
 277
 278        if (keys[0].fmr_physical > 0)
 279                return 0;
 280
 281        /* Fabricate an rmap entry for the external log device. */
 282        irec.fmr_physical = journal->j_blk_offset;
 283        irec.fmr_length = journal->j_total_len;
 284        irec.fmr_owner = EXT4_FMR_OWN_LOG;
 285        irec.fmr_flags = 0;
 286
 287        return ext4_getfsmap_helper(sb, info, &irec);
 288}
 289
 290/* Helper to fill out an ext4_fsmap. */
 291static inline int ext4_getfsmap_fill(struct list_head *meta_list,
 292                                     ext4_fsblk_t fsb, ext4_fsblk_t len,
 293                                     uint64_t owner)
 294{
 295        struct ext4_fsmap *fsm;
 296
 297        fsm = kmalloc(sizeof(*fsm), GFP_NOFS);
 298        if (!fsm)
 299                return -ENOMEM;
 300        fsm->fmr_device = 0;
 301        fsm->fmr_flags = 0;
 302        fsm->fmr_physical = fsb;
 303        fsm->fmr_owner = owner;
 304        fsm->fmr_length = len;
 305        list_add_tail(&fsm->fmr_list, meta_list);
 306
 307        return 0;
 308}
 309
 310/*
 311 * This function returns the number of file system metadata blocks at
 312 * the beginning of a block group, including the reserved gdt blocks.
 313 */
 314static unsigned int ext4_getfsmap_find_sb(struct super_block *sb,
 315                                          ext4_group_t agno,
 316                                          struct list_head *meta_list)
 317{
 318        struct ext4_sb_info *sbi = EXT4_SB(sb);
 319        ext4_fsblk_t fsb = ext4_group_first_block_no(sb, agno);
 320        ext4_fsblk_t len;
 321        unsigned long first_meta_bg = le32_to_cpu(sbi->s_es->s_first_meta_bg);
 322        unsigned long metagroup = agno / EXT4_DESC_PER_BLOCK(sb);
 323        int error;
 324
 325        /* Record the superblock. */
 326        if (ext4_bg_has_super(sb, agno)) {
 327                error = ext4_getfsmap_fill(meta_list, fsb, 1, EXT4_FMR_OWN_FS);
 328                if (error)
 329                        return error;
 330                fsb++;
 331        }
 332
 333        /* Record the group descriptors. */
 334        len = ext4_bg_num_gdb(sb, agno);
 335        if (!len)
 336                return 0;
 337        error = ext4_getfsmap_fill(meta_list, fsb, len,
 338                                   EXT4_FMR_OWN_GDT);
 339        if (error)
 340                return error;
 341        fsb += len;
 342
 343        /* Reserved GDT blocks */
 344        if (!ext4_has_feature_meta_bg(sb) || metagroup < first_meta_bg) {
 345                len = le16_to_cpu(sbi->s_es->s_reserved_gdt_blocks);
 346                error = ext4_getfsmap_fill(meta_list, fsb, len,
 347                                           EXT4_FMR_OWN_RESV_GDT);
 348                if (error)
 349                        return error;
 350        }
 351
 352        return 0;
 353}
 354
 355/* Compare two fsmap items. */
 356static int ext4_getfsmap_compare(void *priv,
 357                                 struct list_head *a,
 358                                 struct list_head *b)
 359{
 360        struct ext4_fsmap *fa;
 361        struct ext4_fsmap *fb;
 362
 363        fa = container_of(a, struct ext4_fsmap, fmr_list);
 364        fb = container_of(b, struct ext4_fsmap, fmr_list);
 365        if (fa->fmr_physical < fb->fmr_physical)
 366                return -1;
 367        else if (fa->fmr_physical > fb->fmr_physical)
 368                return 1;
 369        return 0;
 370}
 371
 372/* Merge adjacent extents of fixed metadata. */
 373static void ext4_getfsmap_merge_fixed_metadata(struct list_head *meta_list)
 374{
 375        struct ext4_fsmap *p;
 376        struct ext4_fsmap *prev = NULL;
 377        struct ext4_fsmap *tmp;
 378
 379        list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
 380                if (!prev) {
 381                        prev = p;
 382                        continue;
 383                }
 384
 385                if (prev->fmr_owner == p->fmr_owner &&
 386                    prev->fmr_physical + prev->fmr_length == p->fmr_physical) {
 387                        prev->fmr_length += p->fmr_length;
 388                        list_del(&p->fmr_list);
 389                        kfree(p);
 390                } else
 391                        prev = p;
 392        }
 393}
 394
 395/* Free a list of fixed metadata. */
 396static void ext4_getfsmap_free_fixed_metadata(struct list_head *meta_list)
 397{
 398        struct ext4_fsmap *p;
 399        struct ext4_fsmap *tmp;
 400
 401        list_for_each_entry_safe(p, tmp, meta_list, fmr_list) {
 402                list_del(&p->fmr_list);
 403                kfree(p);
 404        }
 405}
 406
 407/* Find all the fixed metadata in the filesystem. */
 408static int ext4_getfsmap_find_fixed_metadata(struct super_block *sb,
 409                                             struct list_head *meta_list)
 410{
 411        struct ext4_group_desc *gdp;
 412        ext4_group_t agno;
 413        int error;
 414
 415        INIT_LIST_HEAD(meta_list);
 416
 417        /* Collect everything. */
 418        for (agno = 0; agno < EXT4_SB(sb)->s_groups_count; agno++) {
 419                gdp = ext4_get_group_desc(sb, agno, NULL);
 420                if (!gdp) {
 421                        error = -EFSCORRUPTED;
 422                        goto err;
 423                }
 424
 425                /* Superblock & GDT */
 426                error = ext4_getfsmap_find_sb(sb, agno, meta_list);
 427                if (error)
 428                        goto err;
 429
 430                /* Block bitmap */
 431                error = ext4_getfsmap_fill(meta_list,
 432                                           ext4_block_bitmap(sb, gdp), 1,
 433                                           EXT4_FMR_OWN_BLKBM);
 434                if (error)
 435                        goto err;
 436
 437                /* Inode bitmap */
 438                error = ext4_getfsmap_fill(meta_list,
 439                                           ext4_inode_bitmap(sb, gdp), 1,
 440                                           EXT4_FMR_OWN_INOBM);
 441                if (error)
 442                        goto err;
 443
 444                /* Inodes */
 445                error = ext4_getfsmap_fill(meta_list,
 446                                           ext4_inode_table(sb, gdp),
 447                                           EXT4_SB(sb)->s_itb_per_group,
 448                                           EXT4_FMR_OWN_INODES);
 449                if (error)
 450                        goto err;
 451        }
 452
 453        /* Sort the list */
 454        list_sort(NULL, meta_list, ext4_getfsmap_compare);
 455
 456        /* Merge adjacent extents */
 457        ext4_getfsmap_merge_fixed_metadata(meta_list);
 458
 459        return 0;
 460err:
 461        ext4_getfsmap_free_fixed_metadata(meta_list);
 462        return error;
 463}
 464
 465/* Execute a getfsmap query against the buddy bitmaps */
 466static int ext4_getfsmap_datadev(struct super_block *sb,
 467                                 struct ext4_fsmap *keys,
 468                                 struct ext4_getfsmap_info *info)
 469{
 470        struct ext4_sb_info *sbi = EXT4_SB(sb);
 471        ext4_fsblk_t start_fsb;
 472        ext4_fsblk_t end_fsb;
 473        ext4_fsblk_t bofs;
 474        ext4_fsblk_t eofs;
 475        ext4_group_t start_ag;
 476        ext4_group_t end_ag;
 477        ext4_grpblk_t first_cluster;
 478        ext4_grpblk_t last_cluster;
 479        int error = 0;
 480
 481        bofs = le32_to_cpu(sbi->s_es->s_first_data_block);
 482        eofs = ext4_blocks_count(sbi->s_es);
 483        if (keys[0].fmr_physical >= eofs)
 484                return 0;
 485        else if (keys[0].fmr_physical < bofs)
 486                keys[0].fmr_physical = bofs;
 487        if (keys[1].fmr_physical >= eofs)
 488                keys[1].fmr_physical = eofs - 1;
 489        start_fsb = keys[0].fmr_physical;
 490        end_fsb = keys[1].fmr_physical;
 491
 492        /* Determine first and last group to examine based on start and end */
 493        ext4_get_group_no_and_offset(sb, start_fsb, &start_ag, &first_cluster);
 494        ext4_get_group_no_and_offset(sb, end_fsb, &end_ag, &last_cluster);
 495
 496        /*
 497         * Convert the fsmap low/high keys to bg based keys.  Initialize
 498         * low to the fsmap low key and max out the high key to the end
 499         * of the bg.
 500         */
 501        info->gfi_low = keys[0];
 502        info->gfi_low.fmr_physical = EXT4_C2B(sbi, first_cluster);
 503        info->gfi_low.fmr_length = 0;
 504
 505        memset(&info->gfi_high, 0xFF, sizeof(info->gfi_high));
 506
 507        /* Assemble a list of all the fixed-location metadata. */
 508        error = ext4_getfsmap_find_fixed_metadata(sb, &info->gfi_meta_list);
 509        if (error)
 510                goto err;
 511
 512        /* Query each bg */
 513        for (info->gfi_agno = start_ag;
 514             info->gfi_agno <= end_ag;
 515             info->gfi_agno++) {
 516                /*
 517                 * Set the bg high key from the fsmap high key if this
 518                 * is the last bg that we're querying.
 519                 */
 520                if (info->gfi_agno == end_ag) {
 521                        info->gfi_high = keys[1];
 522                        info->gfi_high.fmr_physical = EXT4_C2B(sbi,
 523                                        last_cluster);
 524                        info->gfi_high.fmr_length = 0;
 525                }
 526
 527                trace_ext4_fsmap_low_key(sb, info->gfi_dev, info->gfi_agno,
 528                                info->gfi_low.fmr_physical,
 529                                info->gfi_low.fmr_length,
 530                                info->gfi_low.fmr_owner);
 531
 532                trace_ext4_fsmap_high_key(sb, info->gfi_dev, info->gfi_agno,
 533                                info->gfi_high.fmr_physical,
 534                                info->gfi_high.fmr_length,
 535                                info->gfi_high.fmr_owner);
 536
 537                error = ext4_mballoc_query_range(sb, info->gfi_agno,
 538                                EXT4_B2C(sbi, info->gfi_low.fmr_physical),
 539                                EXT4_B2C(sbi, info->gfi_high.fmr_physical),
 540                                ext4_getfsmap_datadev_helper, info);
 541                if (error)
 542                        goto err;
 543
 544                /*
 545                 * Set the bg low key to the start of the bg prior to
 546                 * moving on to the next bg.
 547                 */
 548                if (info->gfi_agno == start_ag)
 549                        memset(&info->gfi_low, 0, sizeof(info->gfi_low));
 550        }
 551
 552        /* Do we have a retained free extent? */
 553        if (info->gfi_lastfree.fmr_owner) {
 554                error = ext4_getfsmap_helper(sb, info, &info->gfi_lastfree);
 555                if (error)
 556                        goto err;
 557        }
 558
 559        /* Report any gaps at the end of the bg */
 560        info->gfi_last = true;
 561        error = ext4_getfsmap_datadev_helper(sb, end_ag, last_cluster, 0, info);
 562        if (error)
 563                goto err;
 564
 565err:
 566        ext4_getfsmap_free_fixed_metadata(&info->gfi_meta_list);
 567        return error;
 568}
 569
 570/* Do we recognize the device? */
 571static bool ext4_getfsmap_is_valid_device(struct super_block *sb,
 572                                          struct ext4_fsmap *fm)
 573{
 574        if (fm->fmr_device == 0 || fm->fmr_device == UINT_MAX ||
 575            fm->fmr_device == new_encode_dev(sb->s_bdev->bd_dev))
 576                return true;
 577        if (EXT4_SB(sb)->s_journal_bdev &&
 578            fm->fmr_device == new_encode_dev(EXT4_SB(sb)->s_journal_bdev->bd_dev))
 579                return true;
 580        return false;
 581}
 582
 583/* Ensure that the low key is less than the high key. */
 584static bool ext4_getfsmap_check_keys(struct ext4_fsmap *low_key,
 585                                     struct ext4_fsmap *high_key)
 586{
 587        if (low_key->fmr_device > high_key->fmr_device)
 588                return false;
 589        if (low_key->fmr_device < high_key->fmr_device)
 590                return true;
 591
 592        if (low_key->fmr_physical > high_key->fmr_physical)
 593                return false;
 594        if (low_key->fmr_physical < high_key->fmr_physical)
 595                return true;
 596
 597        if (low_key->fmr_owner > high_key->fmr_owner)
 598                return false;
 599        if (low_key->fmr_owner < high_key->fmr_owner)
 600                return true;
 601
 602        return false;
 603}
 604
 605#define EXT4_GETFSMAP_DEVS      2
 606/*
 607 * Get filesystem's extents as described in head, and format for
 608 * output.  Calls formatter to fill the user's buffer until all
 609 * extents are mapped, until the passed-in head->fmh_count slots have
 610 * been filled, or until the formatter short-circuits the loop, if it
 611 * is tracking filled-in extents on its own.
 612 *
 613 * Key to Confusion
 614 * ----------------
 615 * There are multiple levels of keys and counters at work here:
 616 * _fsmap_head.fmh_keys         -- low and high fsmap keys passed in;
 617 *                                 these reflect fs-wide block addrs.
 618 * dkeys                        -- fmh_keys used to query each device;
 619 *                                 these are fmh_keys but w/ the low key
 620 *                                 bumped up by fmr_length.
 621 * _getfsmap_info.gfi_next_fsblk-- next fs block we expect to see; this
 622 *                                 is how we detect gaps in the fsmap
 623 *                                 records and report them.
 624 * _getfsmap_info.gfi_low/high  -- per-bg low/high keys computed from
 625 *                                 dkeys; used to query the free space.
 626 */
 627int ext4_getfsmap(struct super_block *sb, struct ext4_fsmap_head *head,
 628                  ext4_fsmap_format_t formatter, void *arg)
 629{
 630        struct ext4_fsmap dkeys[2];     /* per-dev keys */
 631        struct ext4_getfsmap_dev handlers[EXT4_GETFSMAP_DEVS];
 632        struct ext4_getfsmap_info info = { NULL };
 633        int i;
 634        int error = 0;
 635
 636        if (head->fmh_iflags & ~FMH_IF_VALID)
 637                return -EINVAL;
 638        if (!ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[0]) ||
 639            !ext4_getfsmap_is_valid_device(sb, &head->fmh_keys[1]))
 640                return -EINVAL;
 641
 642        head->fmh_entries = 0;
 643
 644        /* Set up our device handlers. */
 645        memset(handlers, 0, sizeof(handlers));
 646        handlers[0].gfd_dev = new_encode_dev(sb->s_bdev->bd_dev);
 647        handlers[0].gfd_fn = ext4_getfsmap_datadev;
 648        if (EXT4_SB(sb)->s_journal_bdev) {
 649                handlers[1].gfd_dev = new_encode_dev(
 650                                EXT4_SB(sb)->s_journal_bdev->bd_dev);
 651                handlers[1].gfd_fn = ext4_getfsmap_logdev;
 652        }
 653
 654        sort(handlers, EXT4_GETFSMAP_DEVS, sizeof(struct ext4_getfsmap_dev),
 655                        ext4_getfsmap_dev_compare, NULL);
 656
 657        /*
 658         * To continue where we left off, we allow userspace to use the
 659         * last mapping from a previous call as the low key of the next.
 660         * This is identified by a non-zero length in the low key. We
 661         * have to increment the low key in this scenario to ensure we
 662         * don't return the same mapping again, and instead return the
 663         * very next mapping.
 664         *
 665         * Bump the physical offset as there can be no other mapping for
 666         * the same physical block range.
 667         */
 668        dkeys[0] = head->fmh_keys[0];
 669        dkeys[0].fmr_physical += dkeys[0].fmr_length;
 670        dkeys[0].fmr_owner = 0;
 671        dkeys[0].fmr_length = 0;
 672        memset(&dkeys[1], 0xFF, sizeof(struct ext4_fsmap));
 673
 674        if (!ext4_getfsmap_check_keys(dkeys, &head->fmh_keys[1]))
 675                return -EINVAL;
 676
 677        info.gfi_next_fsblk = head->fmh_keys[0].fmr_physical +
 678                          head->fmh_keys[0].fmr_length;
 679        info.gfi_formatter = formatter;
 680        info.gfi_format_arg = arg;
 681        info.gfi_head = head;
 682
 683        /* For each device we support... */
 684        for (i = 0; i < EXT4_GETFSMAP_DEVS; i++) {
 685                /* Is this device within the range the user asked for? */
 686                if (!handlers[i].gfd_fn)
 687                        continue;
 688                if (head->fmh_keys[0].fmr_device > handlers[i].gfd_dev)
 689                        continue;
 690                if (head->fmh_keys[1].fmr_device < handlers[i].gfd_dev)
 691                        break;
 692
 693                /*
 694                 * If this device number matches the high key, we have
 695                 * to pass the high key to the handler to limit the
 696                 * query results.  If the device number exceeds the
 697                 * low key, zero out the low key so that we get
 698                 * everything from the beginning.
 699                 */
 700                if (handlers[i].gfd_dev == head->fmh_keys[1].fmr_device)
 701                        dkeys[1] = head->fmh_keys[1];
 702                if (handlers[i].gfd_dev > head->fmh_keys[0].fmr_device)
 703                        memset(&dkeys[0], 0, sizeof(struct ext4_fsmap));
 704
 705                info.gfi_dev = handlers[i].gfd_dev;
 706                info.gfi_last = false;
 707                info.gfi_agno = -1;
 708                error = handlers[i].gfd_fn(sb, dkeys, &info);
 709                if (error)
 710                        break;
 711                info.gfi_next_fsblk = 0;
 712        }
 713
 714        head->fmh_oflags = FMH_OF_DEV_T;
 715        return error;
 716}
 717