linux/fs/ext4/indirect.c
<<
>>
Prefs
   1/*
   2 *  linux/fs/ext4/indirect.c
   3 *
   4 *  from
   5 *
   6 *  linux/fs/ext4/inode.c
   7 *
   8 * Copyright (C) 1992, 1993, 1994, 1995
   9 * Remy Card (card@masi.ibp.fr)
  10 * Laboratoire MASI - Institut Blaise Pascal
  11 * Universite Pierre et Marie Curie (Paris VI)
  12 *
  13 *  from
  14 *
  15 *  linux/fs/minix/inode.c
  16 *
  17 *  Copyright (C) 1991, 1992  Linus Torvalds
  18 *
  19 *  Goal-directed block allocation by Stephen Tweedie
  20 *      (sct@redhat.com), 1993, 1998
  21 */
  22
  23#include "ext4_jbd2.h"
  24#include "truncate.h"
  25
  26#include <trace/events/ext4.h>
  27
  28typedef struct {
  29        __le32  *p;
  30        __le32  key;
  31        struct buffer_head *bh;
  32} Indirect;
  33
  34static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
  35{
  36        p->key = *(p->p = v);
  37        p->bh = bh;
  38}
  39
  40/**
  41 *      ext4_block_to_path - parse the block number into array of offsets
  42 *      @inode: inode in question (we are only interested in its superblock)
  43 *      @i_block: block number to be parsed
  44 *      @offsets: array to store the offsets in
  45 *      @boundary: set this non-zero if the referred-to block is likely to be
  46 *             followed (on disk) by an indirect block.
  47 *
  48 *      To store the locations of file's data ext4 uses a data structure common
  49 *      for UNIX filesystems - tree of pointers anchored in the inode, with
  50 *      data blocks at leaves and indirect blocks in intermediate nodes.
  51 *      This function translates the block number into path in that tree -
  52 *      return value is the path length and @offsets[n] is the offset of
  53 *      pointer to (n+1)th node in the nth one. If @block is out of range
  54 *      (negative or too large) warning is printed and zero returned.
  55 *
  56 *      Note: function doesn't find node addresses, so no IO is needed. All
  57 *      we need to know is the capacity of indirect blocks (taken from the
  58 *      inode->i_sb).
  59 */
  60
  61/*
  62 * Portability note: the last comparison (check that we fit into triple
  63 * indirect block) is spelled differently, because otherwise on an
  64 * architecture with 32-bit longs and 8Kb pages we might get into trouble
  65 * if our filesystem had 8Kb blocks. We might use long long, but that would
  66 * kill us on x86. Oh, well, at least the sign propagation does not matter -
  67 * i_block would have to be negative in the very beginning, so we would not
  68 * get there at all.
  69 */
  70
  71static int ext4_block_to_path(struct inode *inode,
  72                              ext4_lblk_t i_block,
  73                              ext4_lblk_t offsets[4], int *boundary)
  74{
  75        int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
  76        int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
  77        const long direct_blocks = EXT4_NDIR_BLOCKS,
  78                indirect_blocks = ptrs,
  79                double_blocks = (1 << (ptrs_bits * 2));
  80        int n = 0;
  81        int final = 0;
  82
  83        if (i_block < direct_blocks) {
  84                offsets[n++] = i_block;
  85                final = direct_blocks;
  86        } else if ((i_block -= direct_blocks) < indirect_blocks) {
  87                offsets[n++] = EXT4_IND_BLOCK;
  88                offsets[n++] = i_block;
  89                final = ptrs;
  90        } else if ((i_block -= indirect_blocks) < double_blocks) {
  91                offsets[n++] = EXT4_DIND_BLOCK;
  92                offsets[n++] = i_block >> ptrs_bits;
  93                offsets[n++] = i_block & (ptrs - 1);
  94                final = ptrs;
  95        } else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
  96                offsets[n++] = EXT4_TIND_BLOCK;
  97                offsets[n++] = i_block >> (ptrs_bits * 2);
  98                offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
  99                offsets[n++] = i_block & (ptrs - 1);
 100                final = ptrs;
 101        } else {
 102                ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
 103                             i_block + direct_blocks +
 104                             indirect_blocks + double_blocks, inode->i_ino);
 105        }
 106        if (boundary)
 107                *boundary = final - 1 - (i_block & (ptrs - 1));
 108        return n;
 109}
 110
 111/**
 112 *      ext4_get_branch - read the chain of indirect blocks leading to data
 113 *      @inode: inode in question
 114 *      @depth: depth of the chain (1 - direct pointer, etc.)
 115 *      @offsets: offsets of pointers in inode/indirect blocks
 116 *      @chain: place to store the result
 117 *      @err: here we store the error value
 118 *
 119 *      Function fills the array of triples <key, p, bh> and returns %NULL
 120 *      if everything went OK or the pointer to the last filled triple
 121 *      (incomplete one) otherwise. Upon the return chain[i].key contains
 122 *      the number of (i+1)-th block in the chain (as it is stored in memory,
 123 *      i.e. little-endian 32-bit), chain[i].p contains the address of that
 124 *      number (it points into struct inode for i==0 and into the bh->b_data
 125 *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
 126 *      block for i>0 and NULL for i==0. In other words, it holds the block
 127 *      numbers of the chain, addresses they were taken from (and where we can
 128 *      verify that chain did not change) and buffer_heads hosting these
 129 *      numbers.
 130 *
 131 *      Function stops when it stumbles upon zero pointer (absent block)
 132 *              (pointer to last triple returned, *@err == 0)
 133 *      or when it gets an IO error reading an indirect block
 134 *              (ditto, *@err == -EIO)
 135 *      or when it reads all @depth-1 indirect blocks successfully and finds
 136 *      the whole chain, all way to the data (returns %NULL, *err == 0).
 137 *
 138 *      Need to be called with
 139 *      down_read(&EXT4_I(inode)->i_data_sem)
 140 */
 141static Indirect *ext4_get_branch(struct inode *inode, int depth,
 142                                 ext4_lblk_t  *offsets,
 143                                 Indirect chain[4], int *err)
 144{
 145        struct super_block *sb = inode->i_sb;
 146        Indirect *p = chain;
 147        struct buffer_head *bh;
 148
 149        *err = 0;
 150        /* i_data is not going away, no lock needed */
 151        add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
 152        if (!p->key)
 153                goto no_block;
 154        while (--depth) {
 155                bh = sb_getblk(sb, le32_to_cpu(p->key));
 156                if (unlikely(!bh))
 157                        goto failure;
 158
 159                if (!bh_uptodate_or_lock(bh)) {
 160                        if (bh_submit_read(bh) < 0) {
 161                                put_bh(bh);
 162                                goto failure;
 163                        }
 164                        /* validate block references */
 165                        if (ext4_check_indirect_blockref(inode, bh)) {
 166                                put_bh(bh);
 167                                goto failure;
 168                        }
 169                }
 170
 171                add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
 172                /* Reader: end */
 173                if (!p->key)
 174                        goto no_block;
 175        }
 176        return NULL;
 177
 178failure:
 179        *err = -EIO;
 180no_block:
 181        return p;
 182}
 183
 184/**
 185 *      ext4_find_near - find a place for allocation with sufficient locality
 186 *      @inode: owner
 187 *      @ind: descriptor of indirect block.
 188 *
 189 *      This function returns the preferred place for block allocation.
 190 *      It is used when heuristic for sequential allocation fails.
 191 *      Rules are:
 192 *        + if there is a block to the left of our position - allocate near it.
 193 *        + if pointer will live in indirect block - allocate near that block.
 194 *        + if pointer will live in inode - allocate in the same
 195 *          cylinder group.
 196 *
 197 * In the latter case we colour the starting block by the callers PID to
 198 * prevent it from clashing with concurrent allocations for a different inode
 199 * in the same block group.   The PID is used here so that functionally related
 200 * files will be close-by on-disk.
 201 *
 202 *      Caller must make sure that @ind is valid and will stay that way.
 203 */
 204static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
 205{
 206        struct ext4_inode_info *ei = EXT4_I(inode);
 207        __le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
 208        __le32 *p;
 209
 210        /* Try to find previous block */
 211        for (p = ind->p - 1; p >= start; p--) {
 212                if (*p)
 213                        return le32_to_cpu(*p);
 214        }
 215
 216        /* No such thing, so let's try location of indirect block */
 217        if (ind->bh)
 218                return ind->bh->b_blocknr;
 219
 220        /*
 221         * It is going to be referred to from the inode itself? OK, just put it
 222         * into the same cylinder group then.
 223         */
 224        return ext4_inode_to_goal_block(inode);
 225}
 226
 227/**
 228 *      ext4_find_goal - find a preferred place for allocation.
 229 *      @inode: owner
 230 *      @block:  block we want
 231 *      @partial: pointer to the last triple within a chain
 232 *
 233 *      Normally this function find the preferred place for block allocation,
 234 *      returns it.
 235 *      Because this is only used for non-extent files, we limit the block nr
 236 *      to 32 bits.
 237 */
 238static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
 239                                   Indirect *partial)
 240{
 241        ext4_fsblk_t goal;
 242
 243        /*
 244         * XXX need to get goal block from mballoc's data structures
 245         */
 246
 247        goal = ext4_find_near(inode, partial);
 248        goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
 249        return goal;
 250}
 251
 252/**
 253 *      ext4_blks_to_allocate - Look up the block map and count the number
 254 *      of direct blocks need to be allocated for the given branch.
 255 *
 256 *      @branch: chain of indirect blocks
 257 *      @k: number of blocks need for indirect blocks
 258 *      @blks: number of data blocks to be mapped.
 259 *      @blocks_to_boundary:  the offset in the indirect block
 260 *
 261 *      return the total number of blocks to be allocate, including the
 262 *      direct and indirect blocks.
 263 */
 264static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
 265                                 int blocks_to_boundary)
 266{
 267        unsigned int count = 0;
 268
 269        /*
 270         * Simple case, [t,d]Indirect block(s) has not allocated yet
 271         * then it's clear blocks on that path have not allocated
 272         */
 273        if (k > 0) {
 274                /* right now we don't handle cross boundary allocation */
 275                if (blks < blocks_to_boundary + 1)
 276                        count += blks;
 277                else
 278                        count += blocks_to_boundary + 1;
 279                return count;
 280        }
 281
 282        count++;
 283        while (count < blks && count <= blocks_to_boundary &&
 284                le32_to_cpu(*(branch[0].p + count)) == 0) {
 285                count++;
 286        }
 287        return count;
 288}
 289
 290/**
 291 *      ext4_alloc_blocks: multiple allocate blocks needed for a branch
 292 *      @handle: handle for this transaction
 293 *      @inode: inode which needs allocated blocks
 294 *      @iblock: the logical block to start allocated at
 295 *      @goal: preferred physical block of allocation
 296 *      @indirect_blks: the number of blocks need to allocate for indirect
 297 *                      blocks
 298 *      @blks: number of desired blocks
 299 *      @new_blocks: on return it will store the new block numbers for
 300 *      the indirect blocks(if needed) and the first direct block,
 301 *      @err: on return it will store the error code
 302 *
 303 *      This function will return the number of blocks allocated as
 304 *      requested by the passed-in parameters.
 305 */
 306static int ext4_alloc_blocks(handle_t *handle, struct inode *inode,
 307                             ext4_lblk_t iblock, ext4_fsblk_t goal,
 308                             int indirect_blks, int blks,
 309                             ext4_fsblk_t new_blocks[4], int *err)
 310{
 311        struct ext4_allocation_request ar;
 312        int target, i;
 313        unsigned long count = 0, blk_allocated = 0;
 314        int index = 0;
 315        ext4_fsblk_t current_block = 0;
 316        int ret = 0;
 317
 318        /*
 319         * Here we try to allocate the requested multiple blocks at once,
 320         * on a best-effort basis.
 321         * To build a branch, we should allocate blocks for
 322         * the indirect blocks(if not allocated yet), and at least
 323         * the first direct block of this branch.  That's the
 324         * minimum number of blocks need to allocate(required)
 325         */
 326        /* first we try to allocate the indirect blocks */
 327        target = indirect_blks;
 328        while (target > 0) {
 329                count = target;
 330                /* allocating blocks for indirect blocks and direct blocks */
 331                current_block = ext4_new_meta_blocks(handle, inode, goal,
 332                                                     0, &count, err);
 333                if (*err)
 334                        goto failed_out;
 335
 336                if (unlikely(current_block + count > EXT4_MAX_BLOCK_FILE_PHYS)) {
 337                        EXT4_ERROR_INODE(inode,
 338                                         "current_block %llu + count %lu > %d!",
 339                                         current_block, count,
 340                                         EXT4_MAX_BLOCK_FILE_PHYS);
 341                        *err = -EIO;
 342                        goto failed_out;
 343                }
 344
 345                target -= count;
 346                /* allocate blocks for indirect blocks */
 347                while (index < indirect_blks && count) {
 348                        new_blocks[index++] = current_block++;
 349                        count--;
 350                }
 351                if (count > 0) {
 352                        /*
 353                         * save the new block number
 354                         * for the first direct block
 355                         */
 356                        new_blocks[index] = current_block;
 357                        printk(KERN_INFO "%s returned more blocks than "
 358                                                "requested\n", __func__);
 359                        WARN_ON(1);
 360                        break;
 361                }
 362        }
 363
 364        target = blks - count ;
 365        blk_allocated = count;
 366        if (!target)
 367                goto allocated;
 368        /* Now allocate data blocks */
 369        memset(&ar, 0, sizeof(ar));
 370        ar.inode = inode;
 371        ar.goal = goal;
 372        ar.len = target;
 373        ar.logical = iblock;
 374        if (S_ISREG(inode->i_mode))
 375                /* enable in-core preallocation only for regular files */
 376                ar.flags = EXT4_MB_HINT_DATA;
 377
 378        current_block = ext4_mb_new_blocks(handle, &ar, err);
 379        if (unlikely(current_block + ar.len > EXT4_MAX_BLOCK_FILE_PHYS)) {
 380                EXT4_ERROR_INODE(inode,
 381                                 "current_block %llu + ar.len %d > %d!",
 382                                 current_block, ar.len,
 383                                 EXT4_MAX_BLOCK_FILE_PHYS);
 384                *err = -EIO;
 385                goto failed_out;
 386        }
 387
 388        if (*err && (target == blks)) {
 389                /*
 390                 * if the allocation failed and we didn't allocate
 391                 * any blocks before
 392                 */
 393                goto failed_out;
 394        }
 395        if (!*err) {
 396                if (target == blks) {
 397                        /*
 398                         * save the new block number
 399                         * for the first direct block
 400                         */
 401                        new_blocks[index] = current_block;
 402                }
 403                blk_allocated += ar.len;
 404        }
 405allocated:
 406        /* total number of blocks allocated for direct blocks */
 407        ret = blk_allocated;
 408        *err = 0;
 409        return ret;
 410failed_out:
 411        for (i = 0; i < index; i++)
 412                ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
 413        return ret;
 414}
 415
 416/**
 417 *      ext4_alloc_branch - allocate and set up a chain of blocks.
 418 *      @handle: handle for this transaction
 419 *      @inode: owner
 420 *      @indirect_blks: number of allocated indirect blocks
 421 *      @blks: number of allocated direct blocks
 422 *      @goal: preferred place for allocation
 423 *      @offsets: offsets (in the blocks) to store the pointers to next.
 424 *      @branch: place to store the chain in.
 425 *
 426 *      This function allocates blocks, zeroes out all but the last one,
 427 *      links them into chain and (if we are synchronous) writes them to disk.
 428 *      In other words, it prepares a branch that can be spliced onto the
 429 *      inode. It stores the information about that chain in the branch[], in
 430 *      the same format as ext4_get_branch() would do. We are calling it after
 431 *      we had read the existing part of chain and partial points to the last
 432 *      triple of that (one with zero ->key). Upon the exit we have the same
 433 *      picture as after the successful ext4_get_block(), except that in one
 434 *      place chain is disconnected - *branch->p is still zero (we did not
 435 *      set the last link), but branch->key contains the number that should
 436 *      be placed into *branch->p to fill that gap.
 437 *
 438 *      If allocation fails we free all blocks we've allocated (and forget
 439 *      their buffer_heads) and return the error value the from failed
 440 *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
 441 *      as described above and return 0.
 442 */
 443static int ext4_alloc_branch(handle_t *handle, struct inode *inode,
 444                             ext4_lblk_t iblock, int indirect_blks,
 445                             int *blks, ext4_fsblk_t goal,
 446                             ext4_lblk_t *offsets, Indirect *branch)
 447{
 448        int blocksize = inode->i_sb->s_blocksize;
 449        int i, n = 0;
 450        int err = 0;
 451        struct buffer_head *bh;
 452        int num;
 453        ext4_fsblk_t new_blocks[4];
 454        ext4_fsblk_t current_block;
 455
 456        num = ext4_alloc_blocks(handle, inode, iblock, goal, indirect_blks,
 457                                *blks, new_blocks, &err);
 458        if (err)
 459                return err;
 460
 461        branch[0].key = cpu_to_le32(new_blocks[0]);
 462        /*
 463         * metadata blocks and data blocks are allocated.
 464         */
 465        for (n = 1; n <= indirect_blks;  n++) {
 466                /*
 467                 * Get buffer_head for parent block, zero it out
 468                 * and set the pointer to new one, then send
 469                 * parent to disk.
 470                 */
 471                bh = sb_getblk(inode->i_sb, new_blocks[n-1]);
 472                if (unlikely(!bh)) {
 473                        err = -EIO;
 474                        goto failed;
 475                }
 476
 477                branch[n].bh = bh;
 478                lock_buffer(bh);
 479                BUFFER_TRACE(bh, "call get_create_access");
 480                err = ext4_journal_get_create_access(handle, bh);
 481                if (err) {
 482                        /* Don't brelse(bh) here; it's done in
 483                         * ext4_journal_forget() below */
 484                        unlock_buffer(bh);
 485                        goto failed;
 486                }
 487
 488                memset(bh->b_data, 0, blocksize);
 489                branch[n].p = (__le32 *) bh->b_data + offsets[n];
 490                branch[n].key = cpu_to_le32(new_blocks[n]);
 491                *branch[n].p = branch[n].key;
 492                if (n == indirect_blks) {
 493                        current_block = new_blocks[n];
 494                        /*
 495                         * End of chain, update the last new metablock of
 496                         * the chain to point to the new allocated
 497                         * data blocks numbers
 498                         */
 499                        for (i = 1; i < num; i++)
 500                                *(branch[n].p + i) = cpu_to_le32(++current_block);
 501                }
 502                BUFFER_TRACE(bh, "marking uptodate");
 503                set_buffer_uptodate(bh);
 504                unlock_buffer(bh);
 505
 506                BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
 507                err = ext4_handle_dirty_metadata(handle, inode, bh);
 508                if (err)
 509                        goto failed;
 510        }
 511        *blks = num;
 512        return err;
 513failed:
 514        /* Allocation failed, free what we already allocated */
 515        ext4_free_blocks(handle, inode, NULL, new_blocks[0], 1, 0);
 516        for (i = 1; i <= n ; i++) {
 517                /*
 518                 * branch[i].bh is newly allocated, so there is no
 519                 * need to revoke the block, which is why we don't
 520                 * need to set EXT4_FREE_BLOCKS_METADATA.
 521                 */
 522                ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1,
 523                                 EXT4_FREE_BLOCKS_FORGET);
 524        }
 525        for (i = n+1; i < indirect_blks; i++)
 526                ext4_free_blocks(handle, inode, NULL, new_blocks[i], 1, 0);
 527
 528        ext4_free_blocks(handle, inode, NULL, new_blocks[i], num, 0);
 529
 530        return err;
 531}
 532
 533/**
 534 * ext4_splice_branch - splice the allocated branch onto inode.
 535 * @handle: handle for this transaction
 536 * @inode: owner
 537 * @block: (logical) number of block we are adding
 538 * @chain: chain of indirect blocks (with a missing link - see
 539 *      ext4_alloc_branch)
 540 * @where: location of missing link
 541 * @num:   number of indirect blocks we are adding
 542 * @blks:  number of direct blocks we are adding
 543 *
 544 * This function fills the missing link and does all housekeeping needed in
 545 * inode (->i_blocks, etc.). In case of success we end up with the full
 546 * chain to new block and return 0.
 547 */
 548static int ext4_splice_branch(handle_t *handle, struct inode *inode,
 549                              ext4_lblk_t block, Indirect *where, int num,
 550                              int blks)
 551{
 552        int i;
 553        int err = 0;
 554        ext4_fsblk_t current_block;
 555
 556        /*
 557         * If we're splicing into a [td]indirect block (as opposed to the
 558         * inode) then we need to get write access to the [td]indirect block
 559         * before the splice.
 560         */
 561        if (where->bh) {
 562                BUFFER_TRACE(where->bh, "get_write_access");
 563                err = ext4_journal_get_write_access(handle, where->bh);
 564                if (err)
 565                        goto err_out;
 566        }
 567        /* That's it */
 568
 569        *where->p = where->key;
 570
 571        /*
 572         * Update the host buffer_head or inode to point to more just allocated
 573         * direct blocks blocks
 574         */
 575        if (num == 0 && blks > 1) {
 576                current_block = le32_to_cpu(where->key) + 1;
 577                for (i = 1; i < blks; i++)
 578                        *(where->p + i) = cpu_to_le32(current_block++);
 579        }
 580
 581        /* We are done with atomic stuff, now do the rest of housekeeping */
 582        /* had we spliced it onto indirect block? */
 583        if (where->bh) {
 584                /*
 585                 * If we spliced it onto an indirect block, we haven't
 586                 * altered the inode.  Note however that if it is being spliced
 587                 * onto an indirect block at the very end of the file (the
 588                 * file is growing) then we *will* alter the inode to reflect
 589                 * the new i_size.  But that is not done here - it is done in
 590                 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
 591                 */
 592                jbd_debug(5, "splicing indirect only\n");
 593                BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
 594                err = ext4_handle_dirty_metadata(handle, inode, where->bh);
 595                if (err)
 596                        goto err_out;
 597        } else {
 598                /*
 599                 * OK, we spliced it into the inode itself on a direct block.
 600                 */
 601                ext4_mark_inode_dirty(handle, inode);
 602                jbd_debug(5, "splicing direct\n");
 603        }
 604        return err;
 605
 606err_out:
 607        for (i = 1; i <= num; i++) {
 608                /*
 609                 * branch[i].bh is newly allocated, so there is no
 610                 * need to revoke the block, which is why we don't
 611                 * need to set EXT4_FREE_BLOCKS_METADATA.
 612                 */
 613                ext4_free_blocks(handle, inode, where[i].bh, 0, 1,
 614                                 EXT4_FREE_BLOCKS_FORGET);
 615        }
 616        ext4_free_blocks(handle, inode, NULL, le32_to_cpu(where[num].key),
 617                         blks, 0);
 618
 619        return err;
 620}
 621
 622/*
 623 * The ext4_ind_map_blocks() function handles non-extents inodes
 624 * (i.e., using the traditional indirect/double-indirect i_blocks
 625 * scheme) for ext4_map_blocks().
 626 *
 627 * Allocation strategy is simple: if we have to allocate something, we will
 628 * have to go the whole way to leaf. So let's do it before attaching anything
 629 * to tree, set linkage between the newborn blocks, write them if sync is
 630 * required, recheck the path, free and repeat if check fails, otherwise
 631 * set the last missing link (that will protect us from any truncate-generated
 632 * removals - all blocks on the path are immune now) and possibly force the
 633 * write on the parent block.
 634 * That has a nice additional property: no special recovery from the failed
 635 * allocations is needed - we simply release blocks and do not touch anything
 636 * reachable from inode.
 637 *
 638 * `handle' can be NULL if create == 0.
 639 *
 640 * return > 0, # of blocks mapped or allocated.
 641 * return = 0, if plain lookup failed.
 642 * return < 0, error case.
 643 *
 644 * The ext4_ind_get_blocks() function should be called with
 645 * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
 646 * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
 647 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
 648 * blocks.
 649 */
 650int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
 651                        struct ext4_map_blocks *map,
 652                        int flags)
 653{
 654        int err = -EIO;
 655        ext4_lblk_t offsets[4];
 656        Indirect chain[4];
 657        Indirect *partial;
 658        ext4_fsblk_t goal;
 659        int indirect_blks;
 660        int blocks_to_boundary = 0;
 661        int depth;
 662        int count = 0;
 663        ext4_fsblk_t first_block = 0;
 664
 665        trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
 666        J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
 667        J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
 668        depth = ext4_block_to_path(inode, map->m_lblk, offsets,
 669                                   &blocks_to_boundary);
 670
 671        if (depth == 0)
 672                goto out;
 673
 674        partial = ext4_get_branch(inode, depth, offsets, chain, &err);
 675
 676        /* Simplest case - block found, no allocation needed */
 677        if (!partial) {
 678                first_block = le32_to_cpu(chain[depth - 1].key);
 679                count++;
 680                /*map more blocks*/
 681                while (count < map->m_len && count <= blocks_to_boundary) {
 682                        ext4_fsblk_t blk;
 683
 684                        blk = le32_to_cpu(*(chain[depth-1].p + count));
 685
 686                        if (blk == first_block + count)
 687                                count++;
 688                        else
 689                                break;
 690                }
 691                goto got_it;
 692        }
 693
 694        /* Next simple case - plain lookup or failed read of indirect block */
 695        if ((flags & EXT4_GET_BLOCKS_CREATE) == 0 || err == -EIO)
 696                goto cleanup;
 697
 698        /*
 699         * Okay, we need to do block allocation.
 700        */
 701        if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
 702                                       EXT4_FEATURE_RO_COMPAT_BIGALLOC)) {
 703                EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
 704                                 "non-extent mapped inodes with bigalloc");
 705                return -ENOSPC;
 706        }
 707
 708        goal = ext4_find_goal(inode, map->m_lblk, partial);
 709
 710        /* the number of blocks need to allocate for [d,t]indirect blocks */
 711        indirect_blks = (chain + depth) - partial - 1;
 712
 713        /*
 714         * Next look up the indirect map to count the totoal number of
 715         * direct blocks to allocate for this branch.
 716         */
 717        count = ext4_blks_to_allocate(partial, indirect_blks,
 718                                      map->m_len, blocks_to_boundary);
 719        /*
 720         * Block out ext4_truncate while we alter the tree
 721         */
 722        err = ext4_alloc_branch(handle, inode, map->m_lblk, indirect_blks,
 723                                &count, goal,
 724                                offsets + (partial - chain), partial);
 725
 726        /*
 727         * The ext4_splice_branch call will free and forget any buffers
 728         * on the new chain if there is a failure, but that risks using
 729         * up transaction credits, especially for bitmaps where the
 730         * credits cannot be returned.  Can we handle this somehow?  We
 731         * may need to return -EAGAIN upwards in the worst case.  --sct
 732         */
 733        if (!err)
 734                err = ext4_splice_branch(handle, inode, map->m_lblk,
 735                                         partial, indirect_blks, count);
 736        if (err)
 737                goto cleanup;
 738
 739        map->m_flags |= EXT4_MAP_NEW;
 740
 741        ext4_update_inode_fsync_trans(handle, inode, 1);
 742got_it:
 743        map->m_flags |= EXT4_MAP_MAPPED;
 744        map->m_pblk = le32_to_cpu(chain[depth-1].key);
 745        map->m_len = count;
 746        if (count > blocks_to_boundary)
 747                map->m_flags |= EXT4_MAP_BOUNDARY;
 748        err = count;
 749        /* Clean up and exit */
 750        partial = chain + depth - 1;    /* the whole chain */
 751cleanup:
 752        while (partial > chain) {
 753                BUFFER_TRACE(partial->bh, "call brelse");
 754                brelse(partial->bh);
 755                partial--;
 756        }
 757out:
 758        trace_ext4_ind_map_blocks_exit(inode, map->m_lblk,
 759                                map->m_pblk, map->m_len, err);
 760        return err;
 761}
 762
 763/*
 764 * O_DIRECT for ext3 (or indirect map) based files
 765 *
 766 * If the O_DIRECT write will extend the file then add this inode to the
 767 * orphan list.  So recovery will truncate it back to the original size
 768 * if the machine crashes during the write.
 769 *
 770 * If the O_DIRECT write is intantiating holes inside i_size and the machine
 771 * crashes then stale disk data _may_ be exposed inside the file. But current
 772 * VFS code falls back into buffered path in that case so we are safe.
 773 */
 774ssize_t ext4_ind_direct_IO(int rw, struct kiocb *iocb,
 775                           const struct iovec *iov, loff_t offset,
 776                           unsigned long nr_segs)
 777{
 778        struct file *file = iocb->ki_filp;
 779        struct inode *inode = file->f_mapping->host;
 780        struct ext4_inode_info *ei = EXT4_I(inode);
 781        handle_t *handle;
 782        ssize_t ret;
 783        int orphan = 0;
 784        size_t count = iov_length(iov, nr_segs);
 785        int retries = 0;
 786
 787        if (rw == WRITE) {
 788                loff_t final_size = offset + count;
 789
 790                if (final_size > inode->i_size) {
 791                        /* Credits for sb + inode write */
 792                        handle = ext4_journal_start(inode, 2);
 793                        if (IS_ERR(handle)) {
 794                                ret = PTR_ERR(handle);
 795                                goto out;
 796                        }
 797                        ret = ext4_orphan_add(handle, inode);
 798                        if (ret) {
 799                                ext4_journal_stop(handle);
 800                                goto out;
 801                        }
 802                        orphan = 1;
 803                        ei->i_disksize = inode->i_size;
 804                        ext4_journal_stop(handle);
 805                }
 806        }
 807
 808retry:
 809        if (rw == READ && ext4_should_dioread_nolock(inode)) {
 810                if (unlikely(!list_empty(&ei->i_completed_io_list))) {
 811                        mutex_lock(&inode->i_mutex);
 812                        ext4_flush_completed_IO(inode);
 813                        mutex_unlock(&inode->i_mutex);
 814                }
 815                ret = __blockdev_direct_IO(rw, iocb, inode,
 816                                 inode->i_sb->s_bdev, iov,
 817                                 offset, nr_segs,
 818                                 ext4_get_block, NULL, NULL, 0);
 819        } else {
 820                ret = blockdev_direct_IO(rw, iocb, inode, iov,
 821                                 offset, nr_segs, ext4_get_block);
 822
 823                if (unlikely((rw & WRITE) && ret < 0)) {
 824                        loff_t isize = i_size_read(inode);
 825                        loff_t end = offset + iov_length(iov, nr_segs);
 826
 827                        if (end > isize)
 828                                ext4_truncate_failed_write(inode);
 829                }
 830        }
 831        if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
 832                goto retry;
 833
 834        if (orphan) {
 835                int err;
 836
 837                /* Credits for sb + inode write */
 838                handle = ext4_journal_start(inode, 2);
 839                if (IS_ERR(handle)) {
 840                        /* This is really bad luck. We've written the data
 841                         * but cannot extend i_size. Bail out and pretend
 842                         * the write failed... */
 843                        ret = PTR_ERR(handle);
 844                        if (inode->i_nlink)
 845                                ext4_orphan_del(NULL, inode);
 846
 847                        goto out;
 848                }
 849                if (inode->i_nlink)
 850                        ext4_orphan_del(handle, inode);
 851                if (ret > 0) {
 852                        loff_t end = offset + ret;
 853                        if (end > inode->i_size) {
 854                                ei->i_disksize = end;
 855                                i_size_write(inode, end);
 856                                /*
 857                                 * We're going to return a positive `ret'
 858                                 * here due to non-zero-length I/O, so there's
 859                                 * no way of reporting error returns from
 860                                 * ext4_mark_inode_dirty() to userspace.  So
 861                                 * ignore it.
 862                                 */
 863                                ext4_mark_inode_dirty(handle, inode);
 864                        }
 865                }
 866                err = ext4_journal_stop(handle);
 867                if (ret == 0)
 868                        ret = err;
 869        }
 870out:
 871        return ret;
 872}
 873
 874/*
 875 * Calculate the number of metadata blocks need to reserve
 876 * to allocate a new block at @lblocks for non extent file based file
 877 */
 878int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
 879{
 880        struct ext4_inode_info *ei = EXT4_I(inode);
 881        sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
 882        int blk_bits;
 883
 884        if (lblock < EXT4_NDIR_BLOCKS)
 885                return 0;
 886
 887        lblock -= EXT4_NDIR_BLOCKS;
 888
 889        if (ei->i_da_metadata_calc_len &&
 890            (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
 891                ei->i_da_metadata_calc_len++;
 892                return 0;
 893        }
 894        ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
 895        ei->i_da_metadata_calc_len = 1;
 896        blk_bits = order_base_2(lblock);
 897        return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
 898}
 899
 900int ext4_ind_trans_blocks(struct inode *inode, int nrblocks, int chunk)
 901{
 902        int indirects;
 903
 904        /* if nrblocks are contiguous */
 905        if (chunk) {
 906                /*
 907                 * With N contiguous data blocks, we need at most
 908                 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
 909                 * 2 dindirect blocks, and 1 tindirect block
 910                 */
 911                return DIV_ROUND_UP(nrblocks,
 912                                    EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
 913        }
 914        /*
 915         * if nrblocks are not contiguous, worse case, each block touch
 916         * a indirect block, and each indirect block touch a double indirect
 917         * block, plus a triple indirect block
 918         */
 919        indirects = nrblocks * 2 + 1;
 920        return indirects;
 921}
 922
 923/*
 924 * Truncate transactions can be complex and absolutely huge.  So we need to
 925 * be able to restart the transaction at a conventient checkpoint to make
 926 * sure we don't overflow the journal.
 927 *
 928 * start_transaction gets us a new handle for a truncate transaction,
 929 * and extend_transaction tries to extend the existing one a bit.  If
 930 * extend fails, we need to propagate the failure up and restart the
 931 * transaction in the top-level truncate loop. --sct
 932 */
 933static handle_t *start_transaction(struct inode *inode)
 934{
 935        handle_t *result;
 936
 937        result = ext4_journal_start(inode, ext4_blocks_for_truncate(inode));
 938        if (!IS_ERR(result))
 939                return result;
 940
 941        ext4_std_error(inode->i_sb, PTR_ERR(result));
 942        return result;
 943}
 944
 945/*
 946 * Try to extend this transaction for the purposes of truncation.
 947 *
 948 * Returns 0 if we managed to create more room.  If we can't create more
 949 * room, and the transaction must be restarted we return 1.
 950 */
 951static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
 952{
 953        if (!ext4_handle_valid(handle))
 954                return 0;
 955        if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
 956                return 0;
 957        if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
 958                return 0;
 959        return 1;
 960}
 961
 962/*
 963 * Probably it should be a library function... search for first non-zero word
 964 * or memcmp with zero_page, whatever is better for particular architecture.
 965 * Linus?
 966 */
 967static inline int all_zeroes(__le32 *p, __le32 *q)
 968{
 969        while (p < q)
 970                if (*p++)
 971                        return 0;
 972        return 1;
 973}
 974
 975/**
 976 *      ext4_find_shared - find the indirect blocks for partial truncation.
 977 *      @inode:   inode in question
 978 *      @depth:   depth of the affected branch
 979 *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
 980 *      @chain:   place to store the pointers to partial indirect blocks
 981 *      @top:     place to the (detached) top of branch
 982 *
 983 *      This is a helper function used by ext4_truncate().
 984 *
 985 *      When we do truncate() we may have to clean the ends of several
 986 *      indirect blocks but leave the blocks themselves alive. Block is
 987 *      partially truncated if some data below the new i_size is referred
 988 *      from it (and it is on the path to the first completely truncated
 989 *      data block, indeed).  We have to free the top of that path along
 990 *      with everything to the right of the path. Since no allocation
 991 *      past the truncation point is possible until ext4_truncate()
 992 *      finishes, we may safely do the latter, but top of branch may
 993 *      require special attention - pageout below the truncation point
 994 *      might try to populate it.
 995 *
 996 *      We atomically detach the top of branch from the tree, store the
 997 *      block number of its root in *@top, pointers to buffer_heads of
 998 *      partially truncated blocks - in @chain[].bh and pointers to
 999 *      their last elements that should not be removed - in
1000 *      @chain[].p. Return value is the pointer to last filled element
1001 *      of @chain.
1002 *
1003 *      The work left to caller to do the actual freeing of subtrees:
1004 *              a) free the subtree starting from *@top
1005 *              b) free the subtrees whose roots are stored in
1006 *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
1007 *              c) free the subtrees growing from the inode past the @chain[0].
1008 *                      (no partially truncated stuff there).  */
1009
1010static Indirect *ext4_find_shared(struct inode *inode, int depth,
1011                                  ext4_lblk_t offsets[4], Indirect chain[4],
1012                                  __le32 *top)
1013{
1014        Indirect *partial, *p;
1015        int k, err;
1016
1017        *top = 0;
1018        /* Make k index the deepest non-null offset + 1 */
1019        for (k = depth; k > 1 && !offsets[k-1]; k--)
1020                ;
1021        partial = ext4_get_branch(inode, k, offsets, chain, &err);
1022        /* Writer: pointers */
1023        if (!partial)
1024                partial = chain + k-1;
1025        /*
1026         * If the branch acquired continuation since we've looked at it -
1027         * fine, it should all survive and (new) top doesn't belong to us.
1028         */
1029        if (!partial->key && *partial->p)
1030                /* Writer: end */
1031                goto no_top;
1032        for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
1033                ;
1034        /*
1035         * OK, we've found the last block that must survive. The rest of our
1036         * branch should be detached before unlocking. However, if that rest
1037         * of branch is all ours and does not grow immediately from the inode
1038         * it's easier to cheat and just decrement partial->p.
1039         */
1040        if (p == chain + k - 1 && p > chain) {
1041                p->p--;
1042        } else {
1043                *top = *p->p;
1044                /* Nope, don't do this in ext4.  Must leave the tree intact */
1045#if 0
1046                *p->p = 0;
1047#endif
1048        }
1049        /* Writer: end */
1050
1051        while (partial > p) {
1052                brelse(partial->bh);
1053                partial--;
1054        }
1055no_top:
1056        return partial;
1057}
1058
1059/*
1060 * Zero a number of block pointers in either an inode or an indirect block.
1061 * If we restart the transaction we must again get write access to the
1062 * indirect block for further modification.
1063 *
1064 * We release `count' blocks on disk, but (last - first) may be greater
1065 * than `count' because there can be holes in there.
1066 *
1067 * Return 0 on success, 1 on invalid block range
1068 * and < 0 on fatal error.
1069 */
1070static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
1071                             struct buffer_head *bh,
1072                             ext4_fsblk_t block_to_free,
1073                             unsigned long count, __le32 *first,
1074                             __le32 *last)
1075{
1076        __le32 *p;
1077        int     flags = EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_VALIDATED;
1078        int     err;
1079
1080        if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
1081                flags |= EXT4_FREE_BLOCKS_METADATA;
1082
1083        if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
1084                                   count)) {
1085                EXT4_ERROR_INODE(inode, "attempt to clear invalid "
1086                                 "blocks %llu len %lu",
1087                                 (unsigned long long) block_to_free, count);
1088                return 1;
1089        }
1090
1091        if (try_to_extend_transaction(handle, inode)) {
1092                if (bh) {
1093                        BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
1094                        err = ext4_handle_dirty_metadata(handle, inode, bh);
1095                        if (unlikely(err))
1096                                goto out_err;
1097                }
1098                err = ext4_mark_inode_dirty(handle, inode);
1099                if (unlikely(err))
1100                        goto out_err;
1101                err = ext4_truncate_restart_trans(handle, inode,
1102                                        ext4_blocks_for_truncate(inode));
1103                if (unlikely(err))
1104                        goto out_err;
1105                if (bh) {
1106                        BUFFER_TRACE(bh, "retaking write access");
1107                        err = ext4_journal_get_write_access(handle, bh);
1108                        if (unlikely(err))
1109                                goto out_err;
1110                }
1111        }
1112
1113        for (p = first; p < last; p++)
1114                *p = 0;
1115
1116        ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
1117        return 0;
1118out_err:
1119        ext4_std_error(inode->i_sb, err);
1120        return err;
1121}
1122
1123/**
1124 * ext4_free_data - free a list of data blocks
1125 * @handle:     handle for this transaction
1126 * @inode:      inode we are dealing with
1127 * @this_bh:    indirect buffer_head which contains *@first and *@last
1128 * @first:      array of block numbers
1129 * @last:       points immediately past the end of array
1130 *
1131 * We are freeing all blocks referred from that array (numbers are stored as
1132 * little-endian 32-bit) and updating @inode->i_blocks appropriately.
1133 *
1134 * We accumulate contiguous runs of blocks to free.  Conveniently, if these
1135 * blocks are contiguous then releasing them at one time will only affect one
1136 * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
1137 * actually use a lot of journal space.
1138 *
1139 * @this_bh will be %NULL if @first and @last point into the inode's direct
1140 * block pointers.
1141 */
1142static void ext4_free_data(handle_t *handle, struct inode *inode,
1143                           struct buffer_head *this_bh,
1144                           __le32 *first, __le32 *last)
1145{
1146        ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
1147        unsigned long count = 0;            /* Number of blocks in the run */
1148        __le32 *block_to_free_p = NULL;     /* Pointer into inode/ind
1149                                               corresponding to
1150                                               block_to_free */
1151        ext4_fsblk_t nr;                    /* Current block # */
1152        __le32 *p;                          /* Pointer into inode/ind
1153                                               for current block */
1154        int err = 0;
1155
1156        if (this_bh) {                          /* For indirect block */
1157                BUFFER_TRACE(this_bh, "get_write_access");
1158                err = ext4_journal_get_write_access(handle, this_bh);
1159                /* Important: if we can't update the indirect pointers
1160                 * to the blocks, we can't free them. */
1161                if (err)
1162                        return;
1163        }
1164
1165        for (p = first; p < last; p++) {
1166                nr = le32_to_cpu(*p);
1167                if (nr) {
1168                        /* accumulate blocks to free if they're contiguous */
1169                        if (count == 0) {
1170                                block_to_free = nr;
1171                                block_to_free_p = p;
1172                                count = 1;
1173                        } else if (nr == block_to_free + count) {
1174                                count++;
1175                        } else {
1176                                err = ext4_clear_blocks(handle, inode, this_bh,
1177                                                        block_to_free, count,
1178                                                        block_to_free_p, p);
1179                                if (err)
1180                                        break;
1181                                block_to_free = nr;
1182                                block_to_free_p = p;
1183                                count = 1;
1184                        }
1185                }
1186        }
1187
1188        if (!err && count > 0)
1189                err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
1190                                        count, block_to_free_p, p);
1191        if (err < 0)
1192                /* fatal error */
1193                return;
1194
1195        if (this_bh) {
1196                BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
1197
1198                /*
1199                 * The buffer head should have an attached journal head at this
1200                 * point. However, if the data is corrupted and an indirect
1201                 * block pointed to itself, it would have been detached when
1202                 * the block was cleared. Check for this instead of OOPSing.
1203                 */
1204                if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
1205                        ext4_handle_dirty_metadata(handle, inode, this_bh);
1206                else
1207                        EXT4_ERROR_INODE(inode,
1208                                         "circular indirect block detected at "
1209                                         "block %llu",
1210                                (unsigned long long) this_bh->b_blocknr);
1211        }
1212}
1213
1214/**
1215 *      ext4_free_branches - free an array of branches
1216 *      @handle: JBD handle for this transaction
1217 *      @inode: inode we are dealing with
1218 *      @parent_bh: the buffer_head which contains *@first and *@last
1219 *      @first: array of block numbers
1220 *      @last:  pointer immediately past the end of array
1221 *      @depth: depth of the branches to free
1222 *
1223 *      We are freeing all blocks referred from these branches (numbers are
1224 *      stored as little-endian 32-bit) and updating @inode->i_blocks
1225 *      appropriately.
1226 */
1227static void ext4_free_branches(handle_t *handle, struct inode *inode,
1228                               struct buffer_head *parent_bh,
1229                               __le32 *first, __le32 *last, int depth)
1230{
1231        ext4_fsblk_t nr;
1232        __le32 *p;
1233
1234        if (ext4_handle_is_aborted(handle))
1235                return;
1236
1237        if (depth--) {
1238                struct buffer_head *bh;
1239                int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1240                p = last;
1241                while (--p >= first) {
1242                        nr = le32_to_cpu(*p);
1243                        if (!nr)
1244                                continue;               /* A hole */
1245
1246                        if (!ext4_data_block_valid(EXT4_SB(inode->i_sb),
1247                                                   nr, 1)) {
1248                                EXT4_ERROR_INODE(inode,
1249                                                 "invalid indirect mapped "
1250                                                 "block %lu (level %d)",
1251                                                 (unsigned long) nr, depth);
1252                                break;
1253                        }
1254
1255                        /* Go read the buffer for the next level down */
1256                        bh = sb_bread(inode->i_sb, nr);
1257
1258                        /*
1259                         * A read failure? Report error and clear slot
1260                         * (should be rare).
1261                         */
1262                        if (!bh) {
1263                                EXT4_ERROR_INODE_BLOCK(inode, nr,
1264                                                       "Read failure");
1265                                continue;
1266                        }
1267
1268                        /* This zaps the entire block.  Bottom up. */
1269                        BUFFER_TRACE(bh, "free child branches");
1270                        ext4_free_branches(handle, inode, bh,
1271                                        (__le32 *) bh->b_data,
1272                                        (__le32 *) bh->b_data + addr_per_block,
1273                                        depth);
1274                        brelse(bh);
1275
1276                        /*
1277                         * Everything below this this pointer has been
1278                         * released.  Now let this top-of-subtree go.
1279                         *
1280                         * We want the freeing of this indirect block to be
1281                         * atomic in the journal with the updating of the
1282                         * bitmap block which owns it.  So make some room in
1283                         * the journal.
1284                         *
1285                         * We zero the parent pointer *after* freeing its
1286                         * pointee in the bitmaps, so if extend_transaction()
1287                         * for some reason fails to put the bitmap changes and
1288                         * the release into the same transaction, recovery
1289                         * will merely complain about releasing a free block,
1290                         * rather than leaking blocks.
1291                         */
1292                        if (ext4_handle_is_aborted(handle))
1293                                return;
1294                        if (try_to_extend_transaction(handle, inode)) {
1295                                ext4_mark_inode_dirty(handle, inode);
1296                                ext4_truncate_restart_trans(handle, inode,
1297                                            ext4_blocks_for_truncate(inode));
1298                        }
1299
1300                        /*
1301                         * The forget flag here is critical because if
1302                         * we are journaling (and not doing data
1303                         * journaling), we have to make sure a revoke
1304                         * record is written to prevent the journal
1305                         * replay from overwriting the (former)
1306                         * indirect block if it gets reallocated as a
1307                         * data block.  This must happen in the same
1308                         * transaction where the data blocks are
1309                         * actually freed.
1310                         */
1311                        ext4_free_blocks(handle, inode, NULL, nr, 1,
1312                                         EXT4_FREE_BLOCKS_METADATA|
1313                                         EXT4_FREE_BLOCKS_FORGET);
1314
1315                        if (parent_bh) {
1316                                /*
1317                                 * The block which we have just freed is
1318                                 * pointed to by an indirect block: journal it
1319                                 */
1320                                BUFFER_TRACE(parent_bh, "get_write_access");
1321                                if (!ext4_journal_get_write_access(handle,
1322                                                                   parent_bh)){
1323                                        *p = 0;
1324                                        BUFFER_TRACE(parent_bh,
1325                                        "call ext4_handle_dirty_metadata");
1326                                        ext4_handle_dirty_metadata(handle,
1327                                                                   inode,
1328                                                                   parent_bh);
1329                                }
1330                        }
1331                }
1332        } else {
1333                /* We have reached the bottom of the tree. */
1334                BUFFER_TRACE(parent_bh, "free data blocks");
1335                ext4_free_data(handle, inode, parent_bh, first, last);
1336        }
1337}
1338
1339void ext4_ind_truncate(struct inode *inode)
1340{
1341        handle_t *handle;
1342        struct ext4_inode_info *ei = EXT4_I(inode);
1343        __le32 *i_data = ei->i_data;
1344        int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1345        struct address_space *mapping = inode->i_mapping;
1346        ext4_lblk_t offsets[4];
1347        Indirect chain[4];
1348        Indirect *partial;
1349        __le32 nr = 0;
1350        int n = 0;
1351        ext4_lblk_t last_block, max_block;
1352        loff_t page_len;
1353        unsigned blocksize = inode->i_sb->s_blocksize;
1354        int err;
1355
1356        handle = start_transaction(inode);
1357        if (IS_ERR(handle))
1358                return;         /* AKPM: return what? */
1359
1360        last_block = (inode->i_size + blocksize-1)
1361                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1362        max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1363                                        >> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1364
1365        if (inode->i_size % PAGE_CACHE_SIZE != 0) {
1366                page_len = PAGE_CACHE_SIZE -
1367                        (inode->i_size & (PAGE_CACHE_SIZE - 1));
1368
1369                err = ext4_discard_partial_page_buffers(handle,
1370                        mapping, inode->i_size, page_len, 0);
1371
1372                if (err)
1373                        goto out_stop;
1374        }
1375
1376        if (last_block != max_block) {
1377                n = ext4_block_to_path(inode, last_block, offsets, NULL);
1378                if (n == 0)
1379                        goto out_stop;  /* error */
1380        }
1381
1382        /*
1383         * OK.  This truncate is going to happen.  We add the inode to the
1384         * orphan list, so that if this truncate spans multiple transactions,
1385         * and we crash, we will resume the truncate when the filesystem
1386         * recovers.  It also marks the inode dirty, to catch the new size.
1387         *
1388         * Implication: the file must always be in a sane, consistent
1389         * truncatable state while each transaction commits.
1390         */
1391        if (ext4_orphan_add(handle, inode))
1392                goto out_stop;
1393
1394        /*
1395         * From here we block out all ext4_get_block() callers who want to
1396         * modify the block allocation tree.
1397         */
1398        down_write(&ei->i_data_sem);
1399
1400        ext4_discard_preallocations(inode);
1401
1402        /*
1403         * The orphan list entry will now protect us from any crash which
1404         * occurs before the truncate completes, so it is now safe to propagate
1405         * the new, shorter inode size (held for now in i_size) into the
1406         * on-disk inode. We do this via i_disksize, which is the value which
1407         * ext4 *really* writes onto the disk inode.
1408         */
1409        ei->i_disksize = inode->i_size;
1410
1411        if (last_block == max_block) {
1412                /*
1413                 * It is unnecessary to free any data blocks if last_block is
1414                 * equal to the indirect block limit.
1415                 */
1416                goto out_unlock;
1417        } else if (n == 1) {            /* direct blocks */
1418                ext4_free_data(handle, inode, NULL, i_data+offsets[0],
1419                               i_data + EXT4_NDIR_BLOCKS);
1420                goto do_indirects;
1421        }
1422
1423        partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1424        /* Kill the top of shared branch (not detached) */
1425        if (nr) {
1426                if (partial == chain) {
1427                        /* Shared branch grows from the inode */
1428                        ext4_free_branches(handle, inode, NULL,
1429                                           &nr, &nr+1, (chain+n-1) - partial);
1430                        *partial->p = 0;
1431                        /*
1432                         * We mark the inode dirty prior to restart,
1433                         * and prior to stop.  No need for it here.
1434                         */
1435                } else {
1436                        /* Shared branch grows from an indirect block */
1437                        BUFFER_TRACE(partial->bh, "get_write_access");
1438                        ext4_free_branches(handle, inode, partial->bh,
1439                                        partial->p,
1440                                        partial->p+1, (chain+n-1) - partial);
1441                }
1442        }
1443        /* Clear the ends of indirect blocks on the shared branch */
1444        while (partial > chain) {
1445                ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
1446                                   (__le32*)partial->bh->b_data+addr_per_block,
1447                                   (chain+n-1) - partial);
1448                BUFFER_TRACE(partial->bh, "call brelse");
1449                brelse(partial->bh);
1450                partial--;
1451        }
1452do_indirects:
1453        /* Kill the remaining (whole) subtrees */
1454        switch (offsets[0]) {
1455        default:
1456                nr = i_data[EXT4_IND_BLOCK];
1457                if (nr) {
1458                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1459                        i_data[EXT4_IND_BLOCK] = 0;
1460                }
1461        case EXT4_IND_BLOCK:
1462                nr = i_data[EXT4_DIND_BLOCK];
1463                if (nr) {
1464                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1465                        i_data[EXT4_DIND_BLOCK] = 0;
1466                }
1467        case EXT4_DIND_BLOCK:
1468                nr = i_data[EXT4_TIND_BLOCK];
1469                if (nr) {
1470                        ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1471                        i_data[EXT4_TIND_BLOCK] = 0;
1472                }
1473        case EXT4_TIND_BLOCK:
1474                ;
1475        }
1476
1477out_unlock:
1478        up_write(&ei->i_data_sem);
1479        inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
1480        ext4_mark_inode_dirty(handle, inode);
1481
1482        /*
1483         * In a multi-transaction truncate, we only make the final transaction
1484         * synchronous
1485         */
1486        if (IS_SYNC(inode))
1487                ext4_handle_sync(handle);
1488out_stop:
1489        /*
1490         * If this was a simple ftruncate(), and the file will remain alive
1491         * then we need to clear up the orphan record which we created above.
1492         * However, if this was a real unlink then we were called by
1493         * ext4_delete_inode(), and we allow that function to clean up the
1494         * orphan info for us.
1495         */
1496        if (inode->i_nlink)
1497                ext4_orphan_del(handle, inode);
1498
1499        ext4_journal_stop(handle);
1500        trace_ext4_truncate_exit(inode);
1501}
1502
1503
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.