linux/fs/ext4/indirect.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/fs/ext4/indirect.c
   4 *
   5 *  from
   6 *
   7 *  linux/fs/ext4/inode.c
   8 *
   9 * Copyright (C) 1992, 1993, 1994, 1995
  10 * Remy Card (card@masi.ibp.fr)
  11 * Laboratoire MASI - Institut Blaise Pascal
  12 * Universite Pierre et Marie Curie (Paris VI)
  13 *
  14 *  from
  15 *
  16 *  linux/fs/minix/inode.c
  17 *
  18 *  Copyright (C) 1991, 1992  Linus Torvalds
  19 *
  20 *  Goal-directed block allocation by Stephen Tweedie
  21 *      (sct@redhat.com), 1993, 1998
  22 */
  23
  24#include "ext4_jbd2.h"
  25#include "truncate.h"
  26#include <linux/dax.h>
  27#include <linux/uio.h>
  28
  29#include <trace/events/ext4.h>
  30
  31typedef struct {
  32        __le32  *p;
  33        __le32  key;
  34        struct buffer_head *bh;
  35} Indirect;
  36
  37static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
  38{
  39        p->key = *(p->p = v);
  40        p->bh = bh;
  41}
  42
  43/**
  44 *      ext4_block_to_path - parse the block number into array of offsets
  45 *      @inode: inode in question (we are only interested in its superblock)
  46 *      @i_block: block number to be parsed
  47 *      @offsets: array to store the offsets in
  48 *      @boundary: set this non-zero if the referred-to block is likely to be
  49 *             followed (on disk) by an indirect block.
  50 *
  51 *      To store the locations of file's data ext4 uses a data structure common
  52 *      for UNIX filesystems - tree of pointers anchored in the inode, with
  53 *      data blocks at leaves and indirect blocks in intermediate nodes.
  54 *      This function translates the block number into path in that tree -
  55 *      return value is the path length and @offsets[n] is the offset of
  56 *      pointer to (n+1)th node in the nth one. If @block is out of range
  57 *      (negative or too large) warning is printed and zero returned.
  58 *
  59 *      Note: function doesn't find node addresses, so no IO is needed. All
  60 *      we need to know is the capacity of indirect blocks (taken from the
  61 *      inode->i_sb).
  62 */
  63
  64/*
  65 * Portability note: the last comparison (check that we fit into triple
  66 * indirect block) is spelled differently, because otherwise on an
  67 * architecture with 32-bit longs and 8Kb pages we might get into trouble
  68 * if our filesystem had 8Kb blocks. We might use long long, but that would
  69 * kill us on x86. Oh, well, at least the sign propagation does not matter -
  70 * i_block would have to be negative in the very beginning, so we would not
  71 * get there at all.
  72 */
  73
  74static int ext4_block_to_path(struct inode *inode,
  75                              ext4_lblk_t i_block,
  76                              ext4_lblk_t offsets[4], int *boundary)
  77{
  78        int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
  79        int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
  80        const long direct_blocks = EXT4_NDIR_BLOCKS,
  81                indirect_blocks = ptrs,
  82                double_blocks = (1 << (ptrs_bits * 2));
  83        int n = 0;
  84        int final = 0;
  85
  86        if (i_block < direct_blocks) {
  87                offsets[n++] = i_block;
  88                final = direct_blocks;
  89        } else if ((i_block -= direct_blocks) < indirect_blocks) {
  90                offsets[n++] = EXT4_IND_BLOCK;
  91                offsets[n++] = i_block;
  92                final = ptrs;
  93        } else if ((i_block -= indirect_blocks) < double_blocks) {
  94                offsets[n++] = EXT4_DIND_BLOCK;
  95                offsets[n++] = i_block >> ptrs_bits;
  96                offsets[n++] = i_block & (ptrs - 1);
  97                final = ptrs;
  98        } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
  99                offsets[n++] = EXT4_TIND_BLOCK;
 100                offsets[n++] = i_block >> (ptrs_bits * 2);
 101                offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
 102                offsets[n++] = i_block & (ptrs - 1);
 103                final = ptrs;
 104        } else {
 105                ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
 106                             i_block + direct_blocks +
 107                             indirect_blocks + double_blocks, inode->i_ino);
 108        }
 109        if (boundary)
 110                *boundary = final - 1 - (i_block & (ptrs - 1));
 111        return n;
 112}
 113
 114/**
 115 *      ext4_get_branch - read the chain of indirect blocks leading to data
 116 *      @inode: inode in question
 117 *      @depth: depth of the chain (1 - direct pointer, etc.)
 118 *      @offsets: offsets of pointers in inode/indirect blocks
 119 *      @chain: place to store the result
 120 *      @err: here we store the error value
 121 *
 122 *      Function fills the array of triples <key, p, bh> and returns %NULL
 123 *      if everything went OK or the pointer to the last filled triple
 124 *      (incomplete one) otherwise. Upon the return chain[i].key contains
 125 *      the number of (i+1)-th block in the chain (as it is stored in memory,
 126 *      i.e. little-endian 32-bit), chain[i].p contains the address of that
 127 *      number (it points into struct inode for i==0 and into the bh->b_data
 128 *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
 129 *      block for i>0 and NULL for i==0. In other words, it holds the block
 130 *      numbers of the chain, addresses they were taken from (and where we can
 131 *      verify that chain did not change) and buffer_heads hosting these
 132 *      numbers.
 133 *
 134 *      Function stops when it stumbles upon zero pointer (absent block)
 135 *              (pointer to last triple returned, *@err == 0)
 136 *      or when it gets an IO error reading an indirect block
 137 *              (ditto, *@err == -EIO)
 138 *      or when it reads all @depth-1 indirect blocks successfully and finds
 139 *      the whole chain, all way to the data (returns %NULL, *err == 0).
 140 *
 141 *      Need to be called with
 142 *      down_read(&EXT4_I(inode)->i_data_sem)
 143 */
 144static Indirect *ext4_get_branch(struct inode *inode, int depth,
 145                                 ext4_lblk_t  *offsets,
 146                                 Indirect chain[4], int *err)
 147{
 148        struct super_block *sb = inode->i_sb;
 149        Indirect *p = chain;
 150        struct buffer_head *bh;
 151        int ret = -EIO;
 152
 153        *err = 0;
 154        /* i_data is not going away, no lock needed */
 155        add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
 156        if (!p->key)
 157                goto no_block;
 158        while (--depth) {
 159                bh = sb_getblk(sb, le32_to_cpu(p->key));
 160                if (unlikely(!bh)) {
 161                        ret = -ENOMEM;
 162                        goto failure;
 163                }
 164
 165                if (!bh_uptodate_or_lock(bh)) {
 166                        if (bh_submit_read(bh) < 0) {
 167                                put_bh(bh);
 168                                goto failure;
 169                        }
 170                        /* validate block references */
 171                        if (ext4_check_indirect_blockref(inode, bh)) {
 172                                put_bh(bh);
 173                                goto failure;
 174                        }
 175                }
 176
 177                add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
 178                /* Reader: end */
 179                if (!p->key)
 180                        goto no_block;
 181        }
 182        return NULL;
 183
 184failure:
 185        *err = ret;
 186no_block:
 187        return p;
 188}
 189
 190/**
 191 *      ext4_find_near - find a place for allocation with sufficient locality
 192 *      @inode: owner
 193 *      @ind: descriptor of indirect block.
 194 *
 195 *      This function returns the preferred place for block allocation.
 196 *      It is used when heuristic for sequential allocation fails.
 197 *      Rules are:
 198 *        + if there is a block to the left of our position - allocate near it.
 199 *        + if pointer will live in indirect block - allocate near that block.
 200 *        + if pointer will live in inode - allocate in the same
 201 *          cylinder group.
 202 *
 203 * In the latter case we colour the starting block by the callers PID to
 204 * prevent it from clashing with concurrent allocations for a different inode
 205 * in the same block group.   The PID is used here so that functionally related
 206 * files will be close-by on-disk.
 207 *
 208 *      Caller must make sure that @ind is valid and will stay that way.
 209 */
 210static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
 211{
 212        struct ext4_inode_info *ei = EXT4_I(inode);
 213        __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
 214        __le32 *p;
 215
 216        /* Try to find previous block */
 217        for (p = ind->p - 1; p >= start; p--) {
 218                if (*p)
 219                        return le32_to_cpu(*p);
 220        }
 221
 222        /* No such thing, so let's try location of indirect block */
 223        if (ind->bh)
 224                return ind->bh->b_blocknr;
 225
 226        /*
 227         * It is going to be referred to from the inode itself? OK, just put it
 228         * into the same cylinder group then.
 229         */
 230        return ext4_inode_to_goal_block(inode);
 231}
 232
 233/**
 234 *      ext4_find_goal - find a preferred place for allocation.
 235 *      @inode: owner
 236 *      @block:  block we want
 237 *      @partial: pointer to the last triple within a chain
 238 *
 239 *      Normally this function find the preferred place for block allocation,
 240 *      returns it.
 241 *      Because this is only used for non-extent files, we limit the block nr
 242 *      to 32 bits.
 243 */
 244static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
 245                                   Indirect *partial)
 246{
 247        ext4_fsblk_t goal;
 248
 249        /*
 250         * XXX need to get goal block from mballoc's data structures
 251         */
 252
 253        goal = ext4_find_near(inode, partial);
 254        goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
 255        return goal;
 256}
 257
 258/**
 259 *      ext4_blks_to_allocate - Look up the block map and count the number
 260 *      of direct blocks need to be allocated for the given branch.
 261 *
 262 *      @branch: chain of indirect blocks
 263 *      @k: number of blocks need for indirect blocks
 264 *      @blks: number of data blocks to be mapped.
 265 *      @blocks_to_boundary:  the offset in the indirect block
 266 *
 267 *      return the total number of blocks to be allocate, including the
 268 *      direct and indirect blocks.
 269 */
 270static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
 271                                 int blocks_to_boundary)
 272{
 273        unsigned int count = 0;
 274
 275        /*
 276         * Simple case, [t,d]Indirect block(s) has not allocated yet
 277         * then it's clear blocks on that path have not allocated
 278         */
 279        if (k > 0) {
 280                /* right now we don't handle cross boundary allocation */
 281                if (blks < blocks_to_boundary + 1)
 282                        count += blks;
 283                else
 284                        count += blocks_to_boundary + 1;
 285                return count;
 286        }
 287
 288        count++;
 289        while (count < blks && count <= blocks_to_boundary &&
 290                le32_to_cpu(*(branch[0].p + count)) == 0) {
 291                count++;
 292        }
 293        return count;
 294}
 295
 296/**
 297 *      ext4_alloc_branch - allocate and set up a chain of blocks.
 298 *      @handle: handle for this transaction
 299 *      @inode: owner
 300 *      @indirect_blks: number of allocated indirect blocks
 301 *      @blks: number of allocated direct blocks
 302 *      @goal: preferred place for allocation
 303 *      @offsets: offsets (in the blocks) to store the pointers to next.
 304 *      @branch: place to store the chain in.
 305 *
 306 *      This function allocates blocks, zeroes out all but the last one,
 307 *      links them into chain and (if we are synchronous) writes them to disk.
 308 *      In other words, it prepares a branch that can be spliced onto the
 309 *      inode. It stores the information about that chain in the branch[], in
 310 *      the same format as ext4_get_branch() would do. We are calling it after
 311 *      we had read the existing part of chain and partial points to the last
 312 *      triple of that (one with zero ->key). Upon the exit we have the same
 313 *      picture as after the successful ext4_get_block(), except that in one
 314 *      place chain is disconnected - *branch->p is still zero (we did not
 315 *      set the last link), but branch->key contains the number that should
 316 *      be placed into *branch->p to fill that gap.
 317 *
 318 *      If allocation fails we free all blocks we've allocated (and forget
 319 *      their buffer_heads) and return the error value the from failed
 320 *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
 321 *      as described above and return 0.
 322 */
 323static int ext4_alloc_branch(handle_t *handle,
 324                             struct ext4_allocation_request *ar,
 325                             int indirect_blks, ext4_lblk_t *offsets,
 326                             Indirect *branch)
 327{
 328        struct buffer_head *            bh;
 329        ext4_fsblk_t                    b, new_blocks[4];
 330        __le32                          *p;
 331        int                             i, j, err, len = 1;
 332
 333        for (i = 0; i <= indirect_blks; i++) {
 334                if (i == indirect_blks) {
 335                        new_blocks[i] = ext4_mb_new_blocks(handle, ar, &err);
 336                } else
 337                        ar->goal = new_blocks[i] = ext4_new_meta_blocks(handle,
 338                                        ar->inode, ar->goal,
 339                                        ar->flags & EXT4_MB_DELALLOC_RESERVED,
 340                                        NULL, &err);
 341                if (err) {
 342                        i--;
 343                        goto failed;
 344                }
 345                branch[i].key = cpu_to_le32(new_blocks[i]);
 346                if (i == 0)
 347                        continue;
 348
 349                bh = branch[i].bh = sb_getblk(ar->inode->i_sb, new_blocks[i-1]);
 350                if (unlikely(!bh)) {
 351                        err = -ENOMEM;
 352                        goto failed;
 353                }
 354                lock_buffer(bh);
 355                BUFFER_TRACE(bh, "call get_create_access");
 356                err = ext4_journal_get_create_access(handle, bh);
 357                if (err) {
 358                        unlock_buffer(bh);
 359                        goto failed;
 360                }
 361
 362                memset(bh->b_data, 0, bh->b_size);
 363                p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
 364                b = new_blocks[i];
 365
 366                if (i == indirect_blks)
 367                        len = ar->len;
 368                for (j = 0; j < len; j++)
 369                        *p++ = cpu_to_le32(b++);
 370
 371                BUFFER_TRACE(bh, "marking uptodate");
 372                set_buffer_uptodate(bh);
 373                unlock_buffer(bh);
 374
 375                BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
 376                err = ext4_handle_dirty_metadata(handle, ar->inode, bh);
 377                if (err)
 378                        goto failed;
 379        }
 380        return 0;
 381failed:
 382        for (; i >= 0; i--) {
 383                /*
 384                 * We want to ext4_forget() only freshly allocated indirect
 385                 * blocks.  Buffer for new_blocks[i-1] is at branch[i].bh and
 386                 * buffer at branch[0].bh is indirect block / inode already
 387                 * existing before ext4_alloc_branch() was called.
 388                 */
 389                if (i > 0 && i != indirect_blks && branch[i].bh)
 390                        ext4_forget(handle, 1, ar->inode, branch[i].bh,
 391                                    branch[i].bh->b_blocknr);
 392                ext4_free_blocks(handle, ar->inode, NULL, new_blocks[i],
 393                                 (i == indirect_blks) ? ar->len : 1, 0);
 394        }
 395        return err;
 396}
 397
 398/**
 399 * ext4_splice_branch - splice the allocated branch onto inode.
 400 * @handle: handle for this transaction
 401 * @inode: owner
 402 * @block: (logical) number of block we are adding
 403 * @chain: chain of indirect blocks (with a missing link - see
 404 *      ext4_alloc_branch)
 405 * @where: location of missing link
 406 * @num:   number of indirect blocks we are adding
 407 * @blks:  number of direct blocks we are adding
 408 *
 409 * This function fills the missing link and does all housekeeping needed in
 410 * inode (->i_blocks, etc.). In case of success we end up with the full
 411 * chain to new block and return 0.
 412 */
 413static int ext4_splice_branch(handle_t *handle,
 414                              struct ext4_allocation_request *ar,
 415                              Indirect *where, int num)
 416{
 417        int i;
 418        int err = 0;
 419        ext4_fsblk_t current_block;
 420
 421        /*
 422         * If we're splicing into a [td]indirect block (as opposed to the
 423         * inode) then we need to get write access to the [td]indirect block
 424         * before the splice.
 425         */
 426        if (where->bh) {
 427                BUFFER_TRACE(where->bh, "get_write_access");
 428                err = ext4_journal_get_write_access(handle, where->bh);
 429                if (err)
 430                        goto err_out;
 431        }
 432        /* That's it */
 433
 434        *where->p = where->key;
 435
 436        /*
 437         * Update the host buffer_head or inode to point to more just allocated
 438         * direct blocks blocks
 439         */
 440        if (num == 0 && ar->len > 1) {
 441                current_block = le32_to_cpu(where->key) + 1;
 442                for (i = 1; i < ar->len; i++)
 443                        *(where->p + i) = cpu_to_le32(current_block++);
 444        }
 445
 446        /* We are done with atomic stuff, now do the rest of housekeeping */
 447        /* had we spliced it onto indirect block? */
 448        if (where->bh) {
 449                /*
 450                 * If we spliced it onto an indirect block, we haven't
 451                 * altered the inode.  Note however that if it is being spliced
 452                 * onto an indirect block at the very end of the file (the
 453                 * file is growing) then we *will* alter the inode to reflect
 454                 * the new i_size.  But that is not done here - it is done in
 455                 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
 456                 */
 457                jbd_debug(5, "splicing indirect only\n");
 458                BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
 459                err = ext4_handle_dirty_metadata(handle, ar->inode, where->bh);
 460                if (err)
 461                        goto err_out;
 462        } else {
 463                /*
 464                 * OK, we spliced it into the inode itself on a direct block.
 465                 */
 466                ext4_mark_inode_dirty(handle, ar->inode);
 467                jbd_debug(5, "splicing direct\n");
 468        }
 469        return err;
 470
 471err_out:
 472        for (i = 1; i <= num; i++) {
 473                /*
 474                 * branch[i].bh is newly allocated, so there is no
 475                 * need to revoke the block, which is why we don't
 476                 * need to set EXT4_FREE_BLOCKS_METADATA.
 477                 */
 478                ext4_free_blocks(handle, ar->inode, where[i].bh, 0, 1,
 479                                 EXT4_FREE_BLOCKS_FORGET);
 480        }
 481        ext4_free_blocks(handle, ar->inode, NULL, le32_to_cpu(where[num].key),
 482                         ar->len, 0);
 483
 484        return err;
 485}
 486
 487/*
 488 * The ext4_ind_map_blocks() function handles non-extents inodes
 489 * (i.e., using the traditional indirect/double-indirect i_blocks
 490 * scheme) for ext4_map_blocks().
 491 *
 492 * Allocation strategy is simple: if we have to allocate something, we will
 493 * have to go the whole way to leaf. So let's do it before attaching anything
 494 * to tree, set linkage between the newborn blocks, write them if sync is
 495 * required, recheck the path, free and repeat if check fails, otherwise
 496 * set the last missing link (that will protect us from any truncate-generated
 497 * removals - all blocks on the path are immune now) and possibly force the
 498 * write on the parent block.
 499 * That has a nice additional property: no special recovery from the failed
 500 * allocations is needed - we simply release blocks and do not touch anything
 501 * reachable from inode.
 502 *
 503 * `handle' can be NULL if create == 0.
 504 *
 505 * return > 0, # of blocks mapped or allocated.
 506 * return = 0, if plain lookup failed.
 507 * return < 0, error case.
 508 *
 509 * The ext4_ind_get_blocks() function should be called with
 510 * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
 511 * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
 512 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
 513 * blocks.
 514 */
 515int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
 516                        struct ext4_map_blocks *map,
 517                        int flags)
 518{
 519        struct ext4_allocation_request ar;
 520        int err = -EIO;
 521        ext4_lblk_t offsets[4];
 522        Indirect chain[4];
 523        Indirect *partial;
 524        int indirect_blks;
 525        int blocks_to_boundary = 0;
 526        int depth;
 527        int count = 0;
 528        ext4_fsblk_t first_block = 0;
 529
 530        trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
 531        J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
 532        J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
 533        depth = ext4_block_to_path(inode, map->m_lblk, offsets,
 534                                   &blocks_to_boundary);
 535
 536        if (depth == 0)
 537                goto out;
 538
 539        partial = ext4_get_branch(inode, depth, offsets, chain, &err);
 540
 541        /* Simplest case - block found, no allocation needed */
 542        if (!partial) {
 543                first_block = le32_to_cpu(chain[depth - 1].key);
 544                count++;
 545                /*map more blocks*/
 546                while (count < map->m_len && count <= blocks_to_boundary) {
 547                        ext4_fsblk_t blk;
 548
 549                        blk = le32_to_cpu(*(chain[depth-1].p + count));
 550
 551                        if (blk == first_block + count)
 552                                count++;
 553                        else
 554                                break;
 555                }
 556                goto got_it;
 557        }
 558
 559        /* Next simple case - plain lookup failed */
 560        if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
 561                unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);
 562                int i;
 563
 564                /* Count number blocks in a subtree under 'partial' */
 565                count = 1;
 566                for (i = 0; partial + i != chain + depth - 1; i++)
 567                        count *= epb;
 568                /* Fill in size of a hole we found */
 569                map->m_pblk = 0;
 570                map->m_len = min_t(unsigned int, map->m_len, count);
 571                goto cleanup;
 572        }
 573
 574        /* Failed read of indirect block */
 575        if (err == -EIO)
 576                goto cleanup;
 577
 578        /*
 579         * Okay, we need to do block allocation.
 580        */
 581        if (ext4_has_feature_bigalloc(inode->i_sb)) {
 582                EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
 583                                 "non-extent mapped inodes with bigalloc");
 584                return -EFSCORRUPTED;
 585        }
 586
 587        /* Set up for the direct block allocation */
 588        memset(&ar, 0, sizeof(ar));
 589        ar.inode = inode;
 590        ar.logical = map->m_lblk;
 591        if (S_ISREG(inode->i_mode))
 592                ar.flags = EXT4_MB_HINT_DATA;
 593        if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
 594                ar.flags |= EXT4_MB_DELALLOC_RESERVED;
 595        if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
 596                ar.flags |= EXT4_MB_USE_RESERVED;
 597
 598        ar.goal = ext4_find_goal(inode, map->m_lblk, partial);
 599
 600        /* the number of blocks need to allocate for [d,t]indirect blocks */
 601        indirect_blks = (chain + depth) - partial - 1;
 602
 603        /*
 604         * Next look up the indirect map to count the totoal number of
 605         * direct blocks to allocate for this branch.
 606         */
 607        ar.len = ext4_blks_to_allocate(partial, indirect_blks,
 608                                       map->m_len, blocks_to_boundary);
 609
 610        /*
 611         * Block out ext4_truncate while we alter the tree
 612         */
 613        err = ext4_alloc_branch(handle, &ar, indirect_blks,
 614                                offsets + (partial - chain), partial);
 615
 616        /*
 617         * The ext4_splice_branch call will free and forget any buffers
 618         * on the new chain if there is a failure, but that risks using
 619         * up transaction credits, especially for bitmaps where the
 620         * credits cannot be returned.  Can we handle this somehow?  We
 621         * may need to return -EAGAIN upwards in the worst case.  --sct
 622         */
 623        if (!err)
 624                err = ext4_splice_branch(handle, &ar, partial, indirect_blks);
 625        if (err)
 626                goto cleanup;
 627
 628        map->m_flags |= EXT4_MAP_NEW;
 629
 630        ext4_update_inode_fsync_trans(handle, inode, 1);
 631        count = ar.len;
 632got_it:
 633        map->m_flags |= EXT4_MAP_MAPPED;
 634        map->m_pblk = le32_to_cpu(chain[depth-1].key);
 635        map->m_len = count;
 636        if (count > blocks_to_boundary)
 637                map->m_flags |= EXT4_MAP_BOUNDARY;
 638        err = count;
 639        /* Clean up and exit */
 640        partial = chain + depth - 1;    /* the whole chain */
 641cleanup:
 642        while (partial > chain) {
 643                BUFFER_TRACE(partial->bh, "call brelse");
 644                brelse(partial->bh);
 645                partial--;
 646        }
 647out:
 648        trace_ext4_ind_map_blocks_exit(inode, flags, map, err);
 649        return err;
 650}
 651
 652/*
 653 * Calculate the number of metadata blocks need to reserve
 654 * to allocate a new block at @lblocks for non extent file based file
 655 */
 656int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
 657{
 658        struct ext4_inode_info *ei = EXT4_I(inode);
 659        sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
 660        int blk_bits;
 661
 662        if (lblock < EXT4_NDIR_BLOCKS)
 663                return 0;
 664
 665        lblock -= EXT4_NDIR_BLOCKS;
 666
 667        if (ei->i_da_metadata_calc_len &&
 668            (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
 669                ei->i_da_metadata_calc_len++;
 670                return 0;
 671        }
 672        ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
 673        ei->i_da_metadata_calc_len = 1;
 674        blk_bits = order_base_2(lblock);
 675        return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
 676}
 677
 678/*
 679 * Calculate number of indirect blocks touched by mapping @nrblocks logically
 680 * contiguous blocks
 681 */
 682int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
 683{
 684        /*
 685         * With N contiguous data blocks, we need at most
 686         * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
 687         * 2 dindirect blocks, and 1 tindirect block
 688         */
 689        return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
 690}
 691
 692/*
 693 * Truncate transactions can be complex and absolutely huge.  So we need to
 694 * be able to restart the transaction at a conventient checkpoint to make
 695 * sure we don't overflow the journal.
 696 *
 697 * Try to extend this transaction for the purposes of truncation.  If
 698 * extend fails, we need to propagate the failure up and restart the
 699 * transaction in the top-level truncate loop. --sct
 700 *
 701 * Returns 0 if we managed to create more room.  If we can't create more
 702 * room, and the transaction must be restarted we return 1.
 703 */
 704static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
 705{
 706        if (!ext4_handle_valid(handle))
 707                return 0;
 708        if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
 709                return 0;
 710        if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
 711                return 0;
 712        return 1;
 713}
 714
 715/*
 716 * Probably it should be a library function... search for first non-zero word
 717 * or memcmp with zero_page, whatever is better for particular architecture.
 718 * Linus?
 719 */
 720static inline int all_zeroes(__le32 *p, __le32 *q)
 721{
 722        while (p < q)
 723                if (*p++)
 724                        return 0;
 725        return 1;
 726}
 727
 728/**
 729 *      ext4_find_shared - find the indirect blocks for partial truncation.
 730 *      @inode:   inode in question
 731 *      @depth:   depth of the affected branch
 732 *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
 733 *      @chain:   place to store the pointers to partial indirect blocks
 734 *      @top:     place to the (detached) top of branch
 735 *
 736 *      This is a helper function used by ext4_truncate().
 737 *
 738 *      When we do truncate() we may have to clean the ends of several
 739 *      indirect blocks but leave the blocks themselves alive. Block is
 740 *      partially truncated if some data below the new i_size is referred
 741 *      from it (and it is on the path to the first completely truncated
 742 *      data block, indeed).  We have to free the top of that path along
 743 *      with everything to the right of the path. Since no allocation
 744 *      past the truncation point is possible until ext4_truncate()
 745 *      finishes, we may safely do the latter, but top of branch may
 746 *      require special attention - pageout below the truncation point
 747 *      might try to populate it.
 748 *
 749 *      We atomically detach the top of branch from the tree, store the
 750 *      block number of its root in *@top, pointers to buffer_heads of
 751 *      partially truncated blocks - in @chain[].bh and pointers to
 752 *      their last elements that should not be removed - in
 753 *      @chain[].p. Return value is the pointer to last filled element
 754 *      of @chain.
 755 *
 756 *      The work left to caller to do the actual freeing of subtrees:
 757 *              a) free the subtree starting from *@top
 758 *              b) free the subtrees whose roots are stored in
 759 *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
 760 *              c) free the subtrees growing from the inode past the @chain[0].
 761 *                      (no partially truncated stuff there).  */
 762
 763static Indirect *ext4_find_shared(struct inode *inode, int depth,
 764                                  ext4_lblk_t offsets[4], Indirect chain[4],
 765                                  __le32 *top)
 766{
 767        Indirect *partial, *p;
 768        int k, err;
 769
 770        *top = 0;
 771        /* Make k index the deepest non-null offset + 1 */
 772        for (k = depth; k > 1 && !offsets[k-1]; k--)
 773                ;
 774        partial = ext4_get_branch(inode, k, offsets, chain, &err);
 775        /* Writer: pointers */
 776        if (!partial)
 777                partial = chain + k-1;
 778        /*
 779         * If the branch acquired continuation since we've looked at it -
 780         * fine, it should all survive and (new) top doesn't belong to us.
 781         */
 782        if (!partial->key && *partial->p)
 783                /* Writer: end */
 784                goto no_top;
 785        for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
 786                ;
 787        /*
 788         * OK, we've found the last block that must survive. The rest of our
 789         * branch should be detached before unlocking. However, if that rest
 790         * of branch is all ours and does not grow immediately from the inode
 791         * it's easier to cheat and just decrement partial->p.
 792         */
 793        if (p == chain + k - 1 && p > chain) {
 794                p->p--;
 795        } else {
 796                *top = *p->p;
 797                /* Nope, don't do this in ext4.  Must leave the tree intact */
 798#if 0
 799                *p->p = 0;
 800#endif
 801        }
 802        /* Writer: end */
 803
 804        while (partial > p) {
 805                brelse(partial->bh);
 806                partial--;
 807        }
 808no_top:
 809        return partial;
 810}
 811
 812/*
 813 * Zero a number of block pointers in either an inode or an indirect block.
 814 * If we restart the transaction we must again get write access to the
 815 * indirect block for further modification.
 816 *
 817 * We release `count' blocks on disk, but (last - first) may be greater
 818 * than `count' because there can be holes in there.
 819 *
 820 * Return 0 on success, 1 on invalid block range
 821 * and < 0 on fatal error.
 822 */
 823static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
 824                             struct buffer_head *bh,
 825                             ext4_fsblk_t block_to_free,
 826                             unsigned long count, __le32 *first,
 827                             __le32 *last)
 828{
 829        __le32 *p;
 830        int     flags = EXT4_FREE_BLOCKS_VALIDATED;
 831        int     err;
 832
 833        if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode) ||
 834            ext4_test_inode_flag(inode, EXT4_INODE_EA_INODE))
 835                flags |= EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_METADATA;
 836        else if (ext4_should_journal_data(inode))
 837                flags |= EXT4_FREE_BLOCKS_FORGET;
 838
 839        if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
 840                                   count)) {
 841                EXT4_ERROR_INODE(inode, "attempt to clear invalid "
 842                                 "blocks %llu len %lu",
 843                                 (unsigned long long) block_to_free, count);
 844                return 1;
 845        }
 846
 847        if (try_to_extend_transaction(handle, inode)) {
 848                if (bh) {
 849                        BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
 850                        err = ext4_handle_dirty_metadata(handle, inode, bh);
 851                        if (unlikely(err))
 852                                goto out_err;
 853                }
 854                err = ext4_mark_inode_dirty(handle, inode);
 855                if (unlikely(err))
 856                        goto out_err;
 857                err = ext4_truncate_restart_trans(handle, inode,
 858                                        ext4_blocks_for_truncate(inode));
 859                if (unlikely(err))
 860                        goto out_err;
 861                if (bh) {
 862                        BUFFER_TRACE(bh, "retaking write access");
 863                        err = ext4_journal_get_write_access(handle, bh);
 864                        if (unlikely(err))
 865                                goto out_err;
 866                }
 867        }
 868
 869        for (p = first; p < last; p++)
 870                *p = 0;
 871
 872        ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
 873        return 0;
 874out_err:
 875        ext4_std_error(inode->i_sb, err);
 876        return err;
 877}
 878
 879/**
 880 * ext4_free_data - free a list of data blocks
 881 * @handle:     handle for this transaction
 882 * @inode:      inode we are dealing with
 883 * @this_bh:    indirect buffer_head which contains *@first and *@last
 884 * @first:      array of block numbers
 885 * @last:       points immediately past the end of array
 886 *
 887 * We are freeing all blocks referred from that array (numbers are stored as
 888 * little-endian 32-bit) and updating @inode->i_blocks appropriately.
 889 *
 890 * We accumulate contiguous runs of blocks to free.  Conveniently, if these
 891 * blocks are contiguous then releasing them at one time will only affect one
 892 * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
 893 * actually use a lot of journal space.
 894 *
 895 * @this_bh will be %NULL if @first and @last point into the inode's direct
 896 * block pointers.
 897 */
 898static void ext4_free_data(handle_t *handle, struct inode *inode,
 899                           struct buffer_head *this_bh,
 900                           __le32 *first, __le32 *last)
 901{
 902        ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
 903        unsigned long count = 0;            /* Number of blocks in the run */
 904        __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
 905                                               corresponding to
 906                                               block_to_free */
 907        ext4_fsblk_t nr;                    /* Current block # */
 908        __le32 *p;                          /* Pointer into inode/ind
 909                                               for current block */
 910        int err = 0;
 911
 912        if (this_bh) {                          /* For indirect block */
 913                BUFFER_TRACE(this_bh, "get_write_access");
 914                err = ext4_journal_get_write_access(handle, this_bh);
 915                /* Important: if we can't update the indirect pointers
 916                 * to the blocks, we can't free them. */
 917                if (err)
 918                        return;
 919        }
 920
 921        for (p = first; p < last; p++) {
 922                nr = le32_to_cpu(*p);
 923                if (nr) {
 924                        /* accumulate blocks to free if they're contiguous */
 925                        if (count == 0) {
 926                                block_to_free = nr;
 927                                block_to_free_p = p;
 928                                count = 1;
 929                        } else if (nr == block_to_free + count) {
 930                                count++;
 931                        } else {
 932                                err = ext4_clear_blocks(handle, inode, this_bh,
 933                                                        block_to_free, count,
 934                                                        block_to_free_p, p);
 935                                if (err)
 936                                        break;
 937                                block_to_free = nr;
 938                                block_to_free_p = p;
 939                                count = 1;
 940                        }
 941                }
 942        }
 943
 944        if (!err && count > 0)
 945                err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
 946                                        count, block_to_free_p, p);
 947        if (err < 0)
 948                /* fatal error */
 949                return;
 950
 951        if (this_bh) {
 952                BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
 953
 954                /*
 955                 * The buffer head should have an attached journal head at this
 956                 * point. However, if the data is corrupted and an indirect
 957                 * block pointed to itself, it would have been detached when
 958                 * the block was cleared. Check for this instead of OOPSing.
 959                 */
 960                if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
 961                        ext4_handle_dirty_metadata(handle, inode, this_bh);
 962                else
 963                        EXT4_ERROR_INODE(inode,
 964                                         "circular indirect block detected at "
 965                                         "block %llu",
 966                                (unsigned long long) this_bh->b_blocknr);
 967        }
 968}
 969
 970/**
 971 *      ext4_free_branches - free an array of branches
 972 *      @handle: JBD handle for this transaction
 973 *      @inode: inode we are dealing with
 974 *      @parent_bh: the buffer_head which contains *@first and *@last
 975 *      @first: array of block numbers
 976 *      @last:  pointer immediately past the end of array
 977 *      @depth: depth of the branches to free
 978 *
 979 *      We are freeing all blocks referred from these branches (numbers are
 980 *      stored as little-endian 32-bit) and updating @inode->i_blocks
 981 *      appropriately.
 982 */
 983static void ext4_free_branches(handle_t *handle, struct inode *inode,
 984                               struct buffer_head *parent_bh,
 985                               __le32 *first, __le32 *last, int depth)
 986{
 987        ext4_fsblk_t nr;
 988        __le32 *p;
 989
 990        if (ext4_handle_is_aborted(handle))
 991                return;
 992
 993        if (depth--) {
 994                struct buffer_head *bh;
 995                int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
 996                p = last;
 997                while (--p >= first) {
 998                        nr = le32_to_cpu(*p);
 999                        if (!nr)
1000                                continue;               /* A hole */
1001
1002                        if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
1003                                                   nr, 1)) {
1004                                EXT4_ERROR_INODE(inode,
1005                                                 "invalid indirect mapped "
1006                                                 "block %lu (level %d)",
1007                                                 (unsigned long) nr, depth);
1008                                break;
1009                        }
1010
1011                        /* Go read the buffer for the next level down */
1012                        bh = sb_bread(inode->i_sb, nr);
1013
1014                        /*
1015                         * A read failure? Report error and clear slot
1016                         * (should be rare).
1017                         */
1018                        if (!bh) {
1019                                EXT4_ERROR_INODE_BLOCK(inode, nr,
1020                                                       "Read failure");
1021                                continue;
1022                        }
1023
1024                        /* This zaps the entire block.  Bottom up. */
1025                        BUFFER_TRACE(bh, "free child branches");
1026                        ext4_free_branches(handle, inode, bh,
1027                                        (__le32 *) bh->b_data,
1028                                        (__le32 *) bh->b_data + addr_per_block,
1029                                        depth);
1030                        brelse(bh);
1031
1032                        /*
1033                         * Everything below this this pointer has been
1034                         * released.  Now let this top-of-subtree go.
1035                         *
1036                         * We want the freeing of this indirect block to be
1037                         * atomic in the journal with the updating of the
1038                         * bitmap block which owns it.  So make some room in
1039                         * the journal.
1040                         *
1041                         * We zero the parent pointer *after* freeing its
1042                         * pointee in the bitmaps, so if extend_transaction()
1043                         * for some reason fails to put the bitmap changes and
1044                         * the release into the same transaction, recovery
1045                         * will merely complain about releasing a free block,
1046                         * rather than leaking blocks.
1047                         */
1048                        if (ext4_handle_is_aborted(handle))
1049                                return;
1050                        if (try_to_extend_transaction(handle, inode)) {
1051                                ext4_mark_inode_dirty(handle, inode);
1052                                ext4_truncate_restart_trans(handle, inode,
1053                                            ext4_blocks_for_truncate(inode));
1054                        }
1055
1056                        /*
1057                         * The forget flag here is critical because if
1058                         * we are journaling (and not doing data
1059                         * journaling), we have to make sure a revoke
1060                         * record is written to prevent the journal
1061                         * replay from overwriting the (former)
1062                         * indirect block if it gets reallocated as a
1063                         * data block.  This must happen in the same
1064                         * transaction where the data blocks are
1065                         * actually freed.
1066                         */
1067                        ext4_free_blocks(handle, inode, NULL, nr, 1,
1068                                         EXT4_FREE_BLOCKS_METADATA|
1069                                         EXT4_FREE_BLOCKS_FORGET);
1070
1071                        if (parent_bh) {
1072                                /*
1073                                 * The block which we have just freed is
1074                                 * pointed to by an indirect block: journal it
1075                                 */
1076                                BUFFER_TRACE(parent_bh, "get_write_access");
1077                                if (!ext4_journal_get_write_access(handle,
1078                                                                   parent_bh)){
1079                                        *p = 0;
1080                                        BUFFER_TRACE(parent_bh,
1081                                        "call ext4_handle_dirty_metadata");
1082                                        ext4_handle_dirty_metadata(handle,
1083                                                                   inode,
1084                                                                   parent_bh);
1085                                }
1086                        }
1087                }
1088        } else {
1089                /* We have reached the bottom of the tree. */
1090                BUFFER_TRACE(parent_bh, "free data blocks");
1091                ext4_free_data(handle, inode, parent_bh, first, last);
1092        }
1093}
1094
1095void ext4_ind_truncate(handle_t *handle, struct inode *inode)
1096{
1097        struct ext4_inode_info *ei = EXT4_I(inode);
1098        __le32 *i_data = ei->i_data;
1099        int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1100        ext4_lblk_t offsets[4];
1101        Indirect chain[4];
1102        Indirect *partial;
1103        __le32 nr = 0;
1104        int n = 0;
1105        ext4_lblk_t last_block, max_block;
1106        unsigned blocksize = inode->i_sb->s_blocksize;
1107
1108        last_block = (inode->i_size + blocksize-1)
1109                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1110        max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1111                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1112
1113        if (last_block != max_block) {
1114                n = ext4_block_to_path(inode, last_block, offsets, NULL);
1115                if (n == 0)
1116                        return;
1117        }
1118
1119        ext4_es_remove_extent(inode, last_block, EXT_MAX_BLOCKS - last_block);
1120
1121        /*
1122         * The orphan list entry will now protect us from any crash which
1123         * occurs before the truncate completes, so it is now safe to propagate
1124         * the new, shorter inode size (held for now in i_size) into the
1125         * on-disk inode. We do this via i_disksize, which is the value which
1126         * ext4 *really* writes onto the disk inode.
1127         */
1128        ei->i_disksize = inode->i_size;
1129
1130        if (last_block == max_block) {
1131                /*
1132                 * It is unnecessary to free any data blocks if last_block is
1133                 * equal to the indirect block limit.
1134                 */
1135                return;
1136        } else if (n == 1) {            /* direct blocks */
1137                ext4_free_data(handle, inode, NULL, i_data+offsets[0],
1138                               i_data + EXT4_NDIR_BLOCKS);
1139                goto do_indirects;
1140        }
1141
1142        partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1143        /* Kill the top of shared branch (not detached) */
1144        if (nr) {
1145                if (partial == chain) {
1146                        /* Shared branch grows from the inode */
1147                        ext4_free_branches(handle, inode, NULL,
1148                                           &nr, &nr+1, (chain+n-1) - partial);
1149                        *partial->p = 0;
1150                        /*
1151                         * We mark the inode dirty prior to restart,
1152                         * and prior to stop.  No need for it here.
1153                         */
1154                } else {
1155                        /* Shared branch grows from an indirect block */
1156                        BUFFER_TRACE(partial->bh, "get_write_access");
1157                        ext4_free_branches(handle, inode, partial->bh,
1158                                        partial->p,
1159                                        partial->p+1, (chain+n-1) - partial);
1160                }
1161        }
1162        /* Clear the ends of indirect blocks on the shared branch */
1163        while (partial > chain) {
1164                ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
1165                                   (__le32*)partial->bh->b_data+addr_per_block,
1166                                   (chain+n-1) - partial);
1167                BUFFER_TRACE(partial->bh, "call brelse");
1168                brelse(partial->bh);
1169                partial--;
1170        }
1171do_indirects:
1172        /* Kill the remaining (whole) subtrees */
1173        switch (offsets[0]) {
1174        default:
1175                nr = i_data[EXT4_IND_BLOCK];
1176                if (nr) {
1177                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1178                        i_data[EXT4_IND_BLOCK] = 0;
1179                }
1180        case EXT4_IND_BLOCK:
1181                nr = i_data[EXT4_DIND_BLOCK];
1182                if (nr) {
1183                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1184                        i_data[EXT4_DIND_BLOCK] = 0;
1185                }
1186        case EXT4_DIND_BLOCK:
1187                nr = i_data[EXT4_TIND_BLOCK];
1188                if (nr) {
1189                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1190                        i_data[EXT4_TIND_BLOCK] = 0;
1191                }
1192        case EXT4_TIND_BLOCK:
1193                ;
1194        }
1195}
1196
1197/**
1198 *      ext4_ind_remove_space - remove space from the range
1199 *      @handle: JBD handle for this transaction
1200 *      @inode: inode we are dealing with
1201 *      @start: First block to remove
1202 *      @end:   One block after the last block to remove (exclusive)
1203 *
1204 *      Free the blocks in the defined range (end is exclusive endpoint of
1205 *      range). This is used by ext4_punch_hole().
1206 */
1207int ext4_ind_remove_space(handle_t *handle, struct inode *inode,
1208                          ext4_lblk_t start, ext4_lblk_t end)
1209{
1210        struct ext4_inode_info *ei = EXT4_I(inode);
1211        __le32 *i_data = ei->i_data;
1212        int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1213        ext4_lblk_t offsets[4], offsets2[4];
1214        Indirect chain[4], chain2[4];
1215        Indirect *partial, *partial2;
1216        ext4_lblk_t max_block;
1217        __le32 nr = 0, nr2 = 0;
1218        int n = 0, n2 = 0;
1219        unsigned blocksize = inode->i_sb->s_blocksize;
1220
1221        max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1222                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1223        if (end >= max_block)
1224                end = max_block;
1225        if ((start >= end) || (start > max_block))
1226                return 0;
1227
1228        n = ext4_block_to_path(inode, start, offsets, NULL);
1229        n2 = ext4_block_to_path(inode, end, offsets2, NULL);
1230
1231        BUG_ON(n > n2);
1232
1233        if ((n == 1) && (n == n2)) {
1234                /* We're punching only within direct block range */
1235                ext4_free_data(handle, inode, NULL, i_data + offsets[0],
1236                               i_data + offsets2[0]);
1237                return 0;
1238        } else if (n2 > n) {
1239                /*
1240                 * Start and end are on a different levels so we're going to
1241                 * free partial block at start, and partial block at end of
1242                 * the range. If there are some levels in between then
1243                 * do_indirects label will take care of that.
1244                 */
1245
1246                if (n == 1) {
1247                        /*
1248                         * Start is at the direct block level, free
1249                         * everything to the end of the level.
1250                         */
1251                        ext4_free_data(handle, inode, NULL, i_data + offsets[0],
1252                                       i_data + EXT4_NDIR_BLOCKS);
1253                        goto end_range;
1254                }
1255
1256
1257                partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1258                if (nr) {
1259                        if (partial == chain) {
1260                                /* Shared branch grows from the inode */
1261                                ext4_free_branches(handle, inode, NULL,
1262                                           &nr, &nr+1, (chain+n-1) - partial);
1263                                *partial->p = 0;
1264                        } else {
1265                                /* Shared branch grows from an indirect block */
1266                                BUFFER_TRACE(partial->bh, "get_write_access");
1267                                ext4_free_branches(handle, inode, partial->bh,
1268                                        partial->p,
1269                                        partial->p+1, (chain+n-1) - partial);
1270                        }
1271                }
1272
1273                /*
1274                 * Clear the ends of indirect blocks on the shared branch
1275                 * at the start of the range
1276                 */
1277                while (partial > chain) {
1278                        ext4_free_branches(handle, inode, partial->bh,
1279                                partial->p + 1,
1280                                (__le32 *)partial->bh->b_data+addr_per_block,
1281                                (chain+n-1) - partial);
1282                        BUFFER_TRACE(partial->bh, "call brelse");
1283                        brelse(partial->bh);
1284                        partial--;
1285                }
1286
1287end_range:
1288                partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
1289                if (nr2) {
1290                        if (partial2 == chain2) {
1291                                /*
1292                                 * Remember, end is exclusive so here we're at
1293                                 * the start of the next level we're not going
1294                                 * to free. Everything was covered by the start
1295                                 * of the range.
1296                                 */
1297                                goto do_indirects;
1298                        }
1299                } else {
1300                        /*
1301                         * ext4_find_shared returns Indirect structure which
1302                         * points to the last element which should not be
1303                         * removed by truncate. But this is end of the range
1304                         * in punch_hole so we need to point to the next element
1305                         */
1306                        partial2->p++;
1307                }
1308
1309                /*
1310                 * Clear the ends of indirect blocks on the shared branch
1311                 * at the end of the range
1312                 */
1313                while (partial2 > chain2) {
1314                        ext4_free_branches(handle, inode, partial2->bh,
1315                                           (__le32 *)partial2->bh->b_data,
1316                                           partial2->p,
1317                                           (chain2+n2-1) - partial2);
1318                        BUFFER_TRACE(partial2->bh, "call brelse");
1319                        brelse(partial2->bh);
1320                        partial2--;
1321                }
1322                goto do_indirects;
1323        }
1324
1325        /* Punch happened within the same level (n == n2) */
1326        partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1327        partial2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
1328
1329        /* Free top, but only if partial2 isn't its subtree. */
1330        if (nr) {
1331                int level = min(partial - chain, partial2 - chain2);
1332                int i;
1333                int subtree = 1;
1334
1335                for (i = 0; i <= level; i++) {
1336                        if (offsets[i] != offsets2[i]) {
1337                                subtree = 0;
1338                                break;
1339                        }
1340                }
1341
1342                if (!subtree) {
1343                        if (partial == chain) {
1344                                /* Shared branch grows from the inode */
1345                                ext4_free_branches(handle, inode, NULL,
1346                                                   &nr, &nr+1,
1347                                                   (chain+n-1) - partial);
1348                                *partial->p = 0;
1349                        } else {
1350                                /* Shared branch grows from an indirect block */
1351                                BUFFER_TRACE(partial->bh, "get_write_access");
1352                                ext4_free_branches(handle, inode, partial->bh,
1353                                                   partial->p,
1354                                                   partial->p+1,
1355                                                   (chain+n-1) - partial);
1356                        }
1357                }
1358        }
1359
1360        if (!nr2) {
1361                /*
1362                 * ext4_find_shared returns Indirect structure which
1363                 * points to the last element which should not be
1364                 * removed by truncate. But this is end of the range
1365                 * in punch_hole so we need to point to the next element
1366                 */
1367                partial2->p++;
1368        }
1369
1370        while (partial > chain || partial2 > chain2) {
1371                int depth = (chain+n-1) - partial;
1372                int depth2 = (chain2+n2-1) - partial2;
1373
1374                if (partial > chain && partial2 > chain2 &&
1375                    partial->bh->b_blocknr == partial2->bh->b_blocknr) {
1376                        /*
1377                         * We've converged on the same block. Clear the range,
1378                         * then we're done.
1379                         */
1380                        ext4_free_branches(handle, inode, partial->bh,
1381                                           partial->p + 1,
1382                                           partial2->p,
1383                                           (chain+n-1) - partial);
1384                        BUFFER_TRACE(partial->bh, "call brelse");
1385                        brelse(partial->bh);
1386                        BUFFER_TRACE(partial2->bh, "call brelse");
1387                        brelse(partial2->bh);
1388                        return 0;
1389                }
1390
1391                /*
1392                 * The start and end partial branches may not be at the same
1393                 * level even though the punch happened within one level. So, we
1394                 * give them a chance to arrive at the same level, then walk
1395                 * them in step with each other until we converge on the same
1396                 * block.
1397                 */
1398                if (partial > chain && depth <= depth2) {
1399                        ext4_free_branches(handle, inode, partial->bh,
1400                                           partial->p + 1,
1401                                           (__le32 *)partial->bh->b_data+addr_per_block,
1402                                           (chain+n-1) - partial);
1403                        BUFFER_TRACE(partial->bh, "call brelse");
1404                        brelse(partial->bh);
1405                        partial--;
1406                }
1407                if (partial2 > chain2 && depth2 <= depth) {
1408                        ext4_free_branches(handle, inode, partial2->bh,
1409                                           (__le32 *)partial2->bh->b_data,
1410                                           partial2->p,
1411                                           (chain2+n2-1) - partial2);
1412                        BUFFER_TRACE(partial2->bh, "call brelse");
1413                        brelse(partial2->bh);
1414                        partial2--;
1415                }
1416        }
1417        return 0;
1418
1419do_indirects:
1420        /* Kill the remaining (whole) subtrees */
1421        switch (offsets[0]) {
1422        default:
1423                if (++n >= n2)
1424                        return 0;
1425                nr = i_data[EXT4_IND_BLOCK];
1426                if (nr) {
1427                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1428                        i_data[EXT4_IND_BLOCK] = 0;
1429                }
1430        case EXT4_IND_BLOCK:
1431                if (++n >= n2)
1432                        return 0;
1433                nr = i_data[EXT4_DIND_BLOCK];
1434                if (nr) {
1435                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1436                        i_data[EXT4_DIND_BLOCK] = 0;
1437                }
1438        case EXT4_DIND_BLOCK:
1439                if (++n >= n2)
1440                        return 0;
1441                nr = i_data[EXT4_TIND_BLOCK];
1442                if (nr) {
1443                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1444                        i_data[EXT4_TIND_BLOCK] = 0;
1445                }
1446        case EXT4_TIND_BLOCK:
1447                ;
1448        }
1449        return 0;
1450}
1451