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 28 typedef struct { 29 __le32 *p; 30 __le32 key; 31 struct buffer_head *bh; 32 } Indirect; 33 34 static 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 71 static 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 */ 141 static 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; 177 178 failure: 179 *err = -EIO; 180 no_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 */ 204 static 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 */ 238 static 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 */ 264 static 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 */ 306 static 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 } 405 allocated: 406 /* total number of blocks allocated for direct blocks */ 407 ret = blk_allocated; 408 *err = 0; 409 return ret; 410 failed_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 */ 443 static 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; 513 failed: 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 */ 548 static 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; 605 606 err_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 */ 650 int 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); 742 got_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 */ 751 cleanup: 752 while (partial > chain) { 753 BUFFER_TRACE(partial->bh, "call brelse"); 754 brelse(partial->bh); 755 partial--; 756 } 757 out: 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 */ 774 ssize_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 } 807 808 retry: 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 } 870 out: 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 */ 878 int 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 } 899 900 int 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 */ 933 static 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 */ 951 static 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 */ 967 static 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 1010 static 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 } 1055 no_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 */ 1070 static 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; 1118 out_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 */ 1142 static 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 */ 1227 static 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 1339 void 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 } 1452 do_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 1477 out_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); 1488 out_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