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