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	unsigned int key;
 152	int ret = -EIO;
 153
 154	*err = 0;
 155	/* i_data is not going away, no lock needed */
 156	add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
 157	if (!p->key)
 158		goto no_block;
 159	while (--depth) {
 160		key = le32_to_cpu(p->key);
 161		if (key > ext4_blocks_count(EXT4_SB(sb)->s_es)) {
 162			/* the block was out of range */
 163			ret = -EFSCORRUPTED;
 164			goto failure;
 165		}
 166		bh = sb_getblk(sb, key);
 167		if (unlikely(!bh)) {
 168			ret = -ENOMEM;
 169			goto failure;
 170		}
 171
 172		if (!bh_uptodate_or_lock(bh)) {
 173			if (ext4_read_bh(bh, 0, NULL) < 0) {
 174				put_bh(bh);
 175				goto failure;
 176			}
 177			/* validate block references */
 178			if (ext4_check_indirect_blockref(inode, bh)) {
 179				put_bh(bh);
 180				goto failure;
 181			}
 182		}
 183
 184		add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
 185		/* Reader: end */
 186		if (!p->key)
 187			goto no_block;
 188	}
 189	return NULL;
 190
 191failure:
 192	*err = ret;
 193no_block:
 194	return p;
 195}
 196
 197/**
 198 *	ext4_find_near - find a place for allocation with sufficient locality
 199 *	@inode: owner
 200 *	@ind: descriptor of indirect block.
 201 *
 202 *	This function returns the preferred place for block allocation.
 203 *	It is used when heuristic for sequential allocation fails.
 204 *	Rules are:
 205 *	  + if there is a block to the left of our position - allocate near it.
 206 *	  + if pointer will live in indirect block - allocate near that block.
 207 *	  + if pointer will live in inode - allocate in the same
 208 *	    cylinder group.
 209 *
 210 * In the latter case we colour the starting block by the callers PID to
 211 * prevent it from clashing with concurrent allocations for a different inode
 212 * in the same block group.   The PID is used here so that functionally related
 213 * files will be close-by on-disk.
 214 *
 215 *	Caller must make sure that @ind is valid and will stay that way.
 216 */
 217static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
 218{
 219	struct ext4_inode_info *ei = EXT4_I(inode);
 220	__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
 221	__le32 *p;
 222
 223	/* Try to find previous block */
 224	for (p = ind->p - 1; p >= start; p--) {
 225		if (*p)
 226			return le32_to_cpu(*p);
 227	}
 228
 229	/* No such thing, so let's try location of indirect block */
 230	if (ind->bh)
 231		return ind->bh->b_blocknr;
 232
 233	/*
 234	 * It is going to be referred to from the inode itself? OK, just put it
 235	 * into the same cylinder group then.
 236	 */
 237	return ext4_inode_to_goal_block(inode);
 238}
 239
 240/**
 241 *	ext4_find_goal - find a preferred place for allocation.
 242 *	@inode: owner
 243 *	@block:  block we want
 244 *	@partial: pointer to the last triple within a chain
 245 *
 246 *	Normally this function find the preferred place for block allocation,
 247 *	returns it.
 248 *	Because this is only used for non-extent files, we limit the block nr
 249 *	to 32 bits.
 250 */
 251static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
 252				   Indirect *partial)
 253{
 254	ext4_fsblk_t goal;
 255
 256	/*
 257	 * XXX need to get goal block from mballoc's data structures
 258	 */
 259
 260	goal = ext4_find_near(inode, partial);
 261	goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
 262	return goal;
 263}
 264
 265/**
 266 *	ext4_blks_to_allocate - Look up the block map and count the number
 267 *	of direct blocks need to be allocated for the given branch.
 268 *
 269 *	@branch: chain of indirect blocks
 270 *	@k: number of blocks need for indirect blocks
 271 *	@blks: number of data blocks to be mapped.
 272 *	@blocks_to_boundary:  the offset in the indirect block
 273 *
 274 *	return the total number of blocks to be allocate, including the
 275 *	direct and indirect blocks.
 276 */
 277static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
 278				 int blocks_to_boundary)
 279{
 280	unsigned int count = 0;
 281
 282	/*
 283	 * Simple case, [t,d]Indirect block(s) has not allocated yet
 284	 * then it's clear blocks on that path have not allocated
 285	 */
 286	if (k > 0) {
 287		/* right now we don't handle cross boundary allocation */
 288		if (blks < blocks_to_boundary + 1)
 289			count += blks;
 290		else
 291			count += blocks_to_boundary + 1;
 292		return count;
 293	}
 294
 295	count++;
 296	while (count < blks && count <= blocks_to_boundary &&
 297		le32_to_cpu(*(branch[0].p + count)) == 0) {
 298		count++;
 299	}
 300	return count;
 301}
 302
 303/**
 304 * ext4_alloc_branch() - allocate and set up a chain of blocks
 305 * @handle: handle for this transaction
 306 * @ar: structure describing the allocation request
 307 * @indirect_blks: number of allocated indirect blocks
 308 * @offsets: offsets (in the blocks) to store the pointers to next.
 309 * @branch: place to store the chain in.
 310 *
 311 *	This function allocates blocks, zeroes out all but the last one,
 312 *	links them into chain and (if we are synchronous) writes them to disk.
 313 *	In other words, it prepares a branch that can be spliced onto the
 314 *	inode. It stores the information about that chain in the branch[], in
 315 *	the same format as ext4_get_branch() would do. We are calling it after
 316 *	we had read the existing part of chain and partial points to the last
 317 *	triple of that (one with zero ->key). Upon the exit we have the same
 318 *	picture as after the successful ext4_get_block(), except that in one
 319 *	place chain is disconnected - *branch->p is still zero (we did not
 320 *	set the last link), but branch->key contains the number that should
 321 *	be placed into *branch->p to fill that gap.
 322 *
 323 *	If allocation fails we free all blocks we've allocated (and forget
 324 *	their buffer_heads) and return the error value the from failed
 325 *	ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
 326 *	as described above and return 0.
 327 */
 328static int ext4_alloc_branch(handle_t *handle,
 329			     struct ext4_allocation_request *ar,
 330			     int indirect_blks, ext4_lblk_t *offsets,
 331			     Indirect *branch)
 332{
 333	struct buffer_head *		bh;
 334	ext4_fsblk_t			b, new_blocks[4];
 335	__le32				*p;
 336	int				i, j, err, len = 1;
 337
 338	for (i = 0; i <= indirect_blks; i++) {
 339		if (i == indirect_blks) {
 340			new_blocks[i] = ext4_mb_new_blocks(handle, ar, &err);
 341		} else {
 342			ar->goal = new_blocks[i] = ext4_new_meta_blocks(handle,
 343					ar->inode, ar->goal,
 344					ar->flags & EXT4_MB_DELALLOC_RESERVED,
 345					NULL, &err);
 346			/* Simplify error cleanup... */
 347			branch[i+1].bh = NULL;
 348		}
 349		if (err) {
 350			i--;
 351			goto failed;
 352		}
 353		branch[i].key = cpu_to_le32(new_blocks[i]);
 354		if (i == 0)
 355			continue;
 356
 357		bh = branch[i].bh = sb_getblk(ar->inode->i_sb, new_blocks[i-1]);
 358		if (unlikely(!bh)) {
 359			err = -ENOMEM;
 360			goto failed;
 361		}
 362		lock_buffer(bh);
 363		BUFFER_TRACE(bh, "call get_create_access");
 364		err = ext4_journal_get_create_access(handle, ar->inode->i_sb,
 365						     bh, EXT4_JTR_NONE);
 366		if (err) {
 367			unlock_buffer(bh);
 368			goto failed;
 369		}
 370
 371		memset(bh->b_data, 0, bh->b_size);
 372		p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
 373		b = new_blocks[i];
 374
 375		if (i == indirect_blks)
 376			len = ar->len;
 377		for (j = 0; j < len; j++)
 378			*p++ = cpu_to_le32(b++);
 379
 380		BUFFER_TRACE(bh, "marking uptodate");
 381		set_buffer_uptodate(bh);
 382		unlock_buffer(bh);
 383
 384		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
 385		err = ext4_handle_dirty_metadata(handle, ar->inode, bh);
 386		if (err)
 387			goto failed;
 388	}
 389	return 0;
 390failed:
 391	if (i == indirect_blks) {
 392		/* Free data blocks */
 393		ext4_free_blocks(handle, ar->inode, NULL, new_blocks[i],
 394				 ar->len, 0);
 395		i--;
 396	}
 397	for (; i >= 0; i--) {
 398		/*
 399		 * We want to ext4_forget() only freshly allocated indirect
 400		 * blocks. Buffer for new_blocks[i] is at branch[i+1].bh
 401		 * (buffer at branch[0].bh is indirect block / inode already
 402		 * existing before ext4_alloc_branch() was called). Also
 403		 * because blocks are freshly allocated, we don't need to
 404		 * revoke them which is why we don't set
 405		 * EXT4_FREE_BLOCKS_METADATA.
 406		 */
 407		ext4_free_blocks(handle, ar->inode, branch[i+1].bh,
 408				 new_blocks[i], 1,
 409				 branch[i+1].bh ? EXT4_FREE_BLOCKS_FORGET : 0);
 410	}
 411	return err;
 412}
 413
 414/**
 415 * ext4_splice_branch() - splice the allocated branch onto inode.
 416 * @handle: handle for this transaction
 417 * @ar: structure describing the allocation request
 418 * @where: location of missing link
 419 * @num:   number of indirect blocks we are adding
 420 *
 421 * This function fills the missing link and does all housekeeping needed in
 422 * inode (->i_blocks, etc.). In case of success we end up with the full
 423 * chain to new block and return 0.
 424 */
 425static int ext4_splice_branch(handle_t *handle,
 426			      struct ext4_allocation_request *ar,
 427			      Indirect *where, int num)
 428{
 429	int i;
 430	int err = 0;
 431	ext4_fsblk_t current_block;
 432
 433	/*
 434	 * If we're splicing into a [td]indirect block (as opposed to the
 435	 * inode) then we need to get write access to the [td]indirect block
 436	 * before the splice.
 437	 */
 438	if (where->bh) {
 439		BUFFER_TRACE(where->bh, "get_write_access");
 440		err = ext4_journal_get_write_access(handle, ar->inode->i_sb,
 441						    where->bh, EXT4_JTR_NONE);
 442		if (err)
 443			goto err_out;
 444	}
 445	/* That's it */
 446
 447	*where->p = where->key;
 448
 449	/*
 450	 * Update the host buffer_head or inode to point to more just allocated
 451	 * direct blocks blocks
 452	 */
 453	if (num == 0 && ar->len > 1) {
 454		current_block = le32_to_cpu(where->key) + 1;
 455		for (i = 1; i < ar->len; i++)
 456			*(where->p + i) = cpu_to_le32(current_block++);
 457	}
 458
 459	/* We are done with atomic stuff, now do the rest of housekeeping */
 460	/* had we spliced it onto indirect block? */
 461	if (where->bh) {
 462		/*
 463		 * If we spliced it onto an indirect block, we haven't
 464		 * altered the inode.  Note however that if it is being spliced
 465		 * onto an indirect block at the very end of the file (the
 466		 * file is growing) then we *will* alter the inode to reflect
 467		 * the new i_size.  But that is not done here - it is done in
 468		 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
 469		 */
 470		ext4_debug("splicing indirect only\n");
 471		BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
 472		err = ext4_handle_dirty_metadata(handle, ar->inode, where->bh);
 473		if (err)
 474			goto err_out;
 475	} else {
 476		/*
 477		 * OK, we spliced it into the inode itself on a direct block.
 478		 */
 479		err = ext4_mark_inode_dirty(handle, ar->inode);
 480		if (unlikely(err))
 481			goto err_out;
 482		ext4_debug("splicing direct\n");
 483	}
 484	return err;
 485
 486err_out:
 487	for (i = 1; i <= num; i++) {
 488		/*
 489		 * branch[i].bh is newly allocated, so there is no
 490		 * need to revoke the block, which is why we don't
 491		 * need to set EXT4_FREE_BLOCKS_METADATA.
 492		 */
 493		ext4_free_blocks(handle, ar->inode, where[i].bh, 0, 1,
 494				 EXT4_FREE_BLOCKS_FORGET);
 495	}
 496	ext4_free_blocks(handle, ar->inode, NULL, le32_to_cpu(where[num].key),
 497			 ar->len, 0);
 498
 499	return err;
 500}
 501
 502/*
 503 * The ext4_ind_map_blocks() function handles non-extents inodes
 504 * (i.e., using the traditional indirect/double-indirect i_blocks
 505 * scheme) for ext4_map_blocks().
 506 *
 507 * Allocation strategy is simple: if we have to allocate something, we will
 508 * have to go the whole way to leaf. So let's do it before attaching anything
 509 * to tree, set linkage between the newborn blocks, write them if sync is
 510 * required, recheck the path, free and repeat if check fails, otherwise
 511 * set the last missing link (that will protect us from any truncate-generated
 512 * removals - all blocks on the path are immune now) and possibly force the
 513 * write on the parent block.
 514 * That has a nice additional property: no special recovery from the failed
 515 * allocations is needed - we simply release blocks and do not touch anything
 516 * reachable from inode.
 517 *
 518 * `handle' can be NULL if create == 0.
 519 *
 520 * return > 0, # of blocks mapped or allocated.
 521 * return = 0, if plain lookup failed.
 522 * return < 0, error case.
 523 *
 524 * The ext4_ind_get_blocks() function should be called with
 525 * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
 526 * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
 527 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
 528 * blocks.
 529 */
 530int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
 531			struct ext4_map_blocks *map,
 532			int flags)
 533{
 534	struct ext4_allocation_request ar;
 535	int err = -EIO;
 536	ext4_lblk_t offsets[4];
 537	Indirect chain[4];
 538	Indirect *partial;
 539	int indirect_blks;
 540	int blocks_to_boundary = 0;
 541	int depth;
 542	int count = 0;
 543	ext4_fsblk_t first_block = 0;
 544
 545	trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
 546	ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
 547	ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
 548	depth = ext4_block_to_path(inode, map->m_lblk, offsets,
 549				   &blocks_to_boundary);
 550
 551	if (depth == 0)
 552		goto out;
 553
 554	partial = ext4_get_branch(inode, depth, offsets, chain, &err);
 555
 556	/* Simplest case - block found, no allocation needed */
 557	if (!partial) {
 558		first_block = le32_to_cpu(chain[depth - 1].key);
 559		count++;
 560		/*map more blocks*/
 561		while (count < map->m_len && count <= blocks_to_boundary) {
 562			ext4_fsblk_t blk;
 563
 564			blk = le32_to_cpu(*(chain[depth-1].p + count));
 565
 566			if (blk == first_block + count)
 567				count++;
 568			else
 569				break;
 570		}
 571		goto got_it;
 572	}
 573
 574	/* Next simple case - plain lookup failed */
 575	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
 576		unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);
 577		int i;
 578
 579		/*
 580		 * Count number blocks in a subtree under 'partial'. At each
 581		 * level we count number of complete empty subtrees beyond
 582		 * current offset and then descend into the subtree only
 583		 * partially beyond current offset.
 584		 */
 585		count = 0;
 586		for (i = partial - chain + 1; i < depth; i++)
 587			count = count * epb + (epb - offsets[i] - 1);
 588		count++;
 589		/* Fill in size of a hole we found */
 590		map->m_pblk = 0;
 591		map->m_len = min_t(unsigned int, map->m_len, count);
 592		goto cleanup;
 593	}
 594
 595	/* Failed read of indirect block */
 596	if (err == -EIO)
 597		goto cleanup;
 598
 599	/*
 600	 * Okay, we need to do block allocation.
 601	*/
 602	if (ext4_has_feature_bigalloc(inode->i_sb)) {
 603		EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
 604				 "non-extent mapped inodes with bigalloc");
 605		err = -EFSCORRUPTED;
 606		goto out;
 607	}
 608
 609	/* Set up for the direct block allocation */
 610	memset(&ar, 0, sizeof(ar));
 611	ar.inode = inode;
 612	ar.logical = map->m_lblk;
 613	if (S_ISREG(inode->i_mode))
 614		ar.flags = EXT4_MB_HINT_DATA;
 615	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
 616		ar.flags |= EXT4_MB_DELALLOC_RESERVED;
 617	if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
 618		ar.flags |= EXT4_MB_USE_RESERVED;
 619
 620	ar.goal = ext4_find_goal(inode, map->m_lblk, partial);
 621
 622	/* the number of blocks need to allocate for [d,t]indirect blocks */
 623	indirect_blks = (chain + depth) - partial - 1;
 624
 625	/*
 626	 * Next look up the indirect map to count the totoal number of
 627	 * direct blocks to allocate for this branch.
 628	 */
 629	ar.len = ext4_blks_to_allocate(partial, indirect_blks,
 630				       map->m_len, blocks_to_boundary);
 631
 632	/*
 633	 * Block out ext4_truncate while we alter the tree
 634	 */
 635	err = ext4_alloc_branch(handle, &ar, indirect_blks,
 636				offsets + (partial - chain), partial);
 637
 638	/*
 639	 * The ext4_splice_branch call will free and forget any buffers
 640	 * on the new chain if there is a failure, but that risks using
 641	 * up transaction credits, especially for bitmaps where the
 642	 * credits cannot be returned.  Can we handle this somehow?  We
 643	 * may need to return -EAGAIN upwards in the worst case.  --sct
 644	 */
 645	if (!err)
 646		err = ext4_splice_branch(handle, &ar, partial, indirect_blks);
 647	if (err)
 648		goto cleanup;
 649
 650	map->m_flags |= EXT4_MAP_NEW;
 651
 652	ext4_update_inode_fsync_trans(handle, inode, 1);
 653	count = ar.len;
 
 
 
 
 
 
 
 
 654got_it:
 655	map->m_flags |= EXT4_MAP_MAPPED;
 656	map->m_pblk = le32_to_cpu(chain[depth-1].key);
 657	map->m_len = count;
 658	if (count > blocks_to_boundary)
 659		map->m_flags |= EXT4_MAP_BOUNDARY;
 660	err = count;
 661	/* Clean up and exit */
 662	partial = chain + depth - 1;	/* the whole chain */
 663cleanup:
 664	while (partial > chain) {
 665		BUFFER_TRACE(partial->bh, "call brelse");
 666		brelse(partial->bh);
 667		partial--;
 668	}
 669out:
 670	trace_ext4_ind_map_blocks_exit(inode, flags, map, err);
 671	return err;
 672}
 673
 674/*
 675 * Calculate number of indirect blocks touched by mapping @nrblocks logically
 676 * contiguous blocks
 677 */
 678int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
 679{
 680	/*
 681	 * With N contiguous data blocks, we need at most
 682	 * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
 683	 * 2 dindirect blocks, and 1 tindirect block
 684	 */
 685	return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
 686}
 687
 688static int ext4_ind_trunc_restart_fn(handle_t *handle, struct inode *inode,
 689				     struct buffer_head *bh, int *dropped)
 690{
 691	int err;
 692
 693	if (bh) {
 694		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
 695		err = ext4_handle_dirty_metadata(handle, inode, bh);
 696		if (unlikely(err))
 697			return err;
 698	}
 699	err = ext4_mark_inode_dirty(handle, inode);
 700	if (unlikely(err))
 701		return err;
 702	/*
 703	 * Drop i_data_sem to avoid deadlock with ext4_map_blocks.  At this
 704	 * moment, get_block can be called only for blocks inside i_size since
 705	 * page cache has been already dropped and writes are blocked by
 706	 * i_rwsem. So we can safely drop the i_data_sem here.
 707	 */
 708	BUG_ON(EXT4_JOURNAL(inode) == NULL);
 709	ext4_discard_preallocations(inode, 0);
 710	up_write(&EXT4_I(inode)->i_data_sem);
 711	*dropped = 1;
 712	return 0;
 713}
 714
 715/*
 716 * Truncate transactions can be complex and absolutely huge.  So we need to
 717 * be able to restart the transaction at a convenient checkpoint to make
 718 * sure we don't overflow the journal.
 719 *
 720 * Try to extend this transaction for the purposes of truncation.  If
 721 * extend fails, we restart transaction.
 722 */
 723static int ext4_ind_truncate_ensure_credits(handle_t *handle,
 724					    struct inode *inode,
 725					    struct buffer_head *bh,
 726					    int revoke_creds)
 727{
 728	int ret;
 729	int dropped = 0;
 730
 731	ret = ext4_journal_ensure_credits_fn(handle, EXT4_RESERVE_TRANS_BLOCKS,
 732			ext4_blocks_for_truncate(inode), revoke_creds,
 733			ext4_ind_trunc_restart_fn(handle, inode, bh, &dropped));
 734	if (dropped)
 735		down_write(&EXT4_I(inode)->i_data_sem);
 736	if (ret <= 0)
 737		return ret;
 738	if (bh) {
 739		BUFFER_TRACE(bh, "retaking write access");
 740		ret = ext4_journal_get_write_access(handle, inode->i_sb, bh,
 741						    EXT4_JTR_NONE);
 742		if (unlikely(ret))
 743			return ret;
 744	}
 745	return 0;
 746}
 747
 748/*
 749 * Probably it should be a library function... search for first non-zero word
 750 * or memcmp with zero_page, whatever is better for particular architecture.
 751 * Linus?
 752 */
 753static inline int all_zeroes(__le32 *p, __le32 *q)
 754{
 755	while (p < q)
 756		if (*p++)
 757			return 0;
 758	return 1;
 759}
 760
 761/**
 762 *	ext4_find_shared - find the indirect blocks for partial truncation.
 763 *	@inode:	  inode in question
 764 *	@depth:	  depth of the affected branch
 765 *	@offsets: offsets of pointers in that branch (see ext4_block_to_path)
 766 *	@chain:	  place to store the pointers to partial indirect blocks
 767 *	@top:	  place to the (detached) top of branch
 768 *
 769 *	This is a helper function used by ext4_truncate().
 770 *
 771 *	When we do truncate() we may have to clean the ends of several
 772 *	indirect blocks but leave the blocks themselves alive. Block is
 773 *	partially truncated if some data below the new i_size is referred
 774 *	from it (and it is on the path to the first completely truncated
 775 *	data block, indeed).  We have to free the top of that path along
 776 *	with everything to the right of the path. Since no allocation
 777 *	past the truncation point is possible until ext4_truncate()
 778 *	finishes, we may safely do the latter, but top of branch may
 779 *	require special attention - pageout below the truncation point
 780 *	might try to populate it.
 781 *
 782 *	We atomically detach the top of branch from the tree, store the
 783 *	block number of its root in *@top, pointers to buffer_heads of
 784 *	partially truncated blocks - in @chain[].bh and pointers to
 785 *	their last elements that should not be removed - in
 786 *	@chain[].p. Return value is the pointer to last filled element
 787 *	of @chain.
 788 *
 789 *	The work left to caller to do the actual freeing of subtrees:
 790 *		a) free the subtree starting from *@top
 791 *		b) free the subtrees whose roots are stored in
 792 *			(@chain[i].p+1 .. end of @chain[i].bh->b_data)
 793 *		c) free the subtrees growing from the inode past the @chain[0].
 794 *			(no partially truncated stuff there).  */
 795
 796static Indirect *ext4_find_shared(struct inode *inode, int depth,
 797				  ext4_lblk_t offsets[4], Indirect chain[4],
 798				  __le32 *top)
 799{
 800	Indirect *partial, *p;
 801	int k, err;
 802
 803	*top = 0;
 804	/* Make k index the deepest non-null offset + 1 */
 805	for (k = depth; k > 1 && !offsets[k-1]; k--)
 806		;
 807	partial = ext4_get_branch(inode, k, offsets, chain, &err);
 808	/* Writer: pointers */
 809	if (!partial)
 810		partial = chain + k-1;
 811	/*
 812	 * If the branch acquired continuation since we've looked at it -
 813	 * fine, it should all survive and (new) top doesn't belong to us.
 814	 */
 815	if (!partial->key && *partial->p)
 816		/* Writer: end */
 817		goto no_top;
 818	for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
 819		;
 820	/*
 821	 * OK, we've found the last block that must survive. The rest of our
 822	 * branch should be detached before unlocking. However, if that rest
 823	 * of branch is all ours and does not grow immediately from the inode
 824	 * it's easier to cheat and just decrement partial->p.
 825	 */
 826	if (p == chain + k - 1 && p > chain) {
 827		p->p--;
 828	} else {
 829		*top = *p->p;
 830		/* Nope, don't do this in ext4.  Must leave the tree intact */
 831#if 0
 832		*p->p = 0;
 833#endif
 834	}
 835	/* Writer: end */
 836
 837	while (partial > p) {
 838		brelse(partial->bh);
 839		partial--;
 840	}
 841no_top:
 842	return partial;
 843}
 844
 845/*
 846 * Zero a number of block pointers in either an inode or an indirect block.
 847 * If we restart the transaction we must again get write access to the
 848 * indirect block for further modification.
 849 *
 850 * We release `count' blocks on disk, but (last - first) may be greater
 851 * than `count' because there can be holes in there.
 852 *
 853 * Return 0 on success, 1 on invalid block range
 854 * and < 0 on fatal error.
 855 */
 856static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
 857			     struct buffer_head *bh,
 858			     ext4_fsblk_t block_to_free,
 859			     unsigned long count, __le32 *first,
 860			     __le32 *last)
 861{
 862	__le32 *p;
 863	int	flags = EXT4_FREE_BLOCKS_VALIDATED;
 864	int	err;
 865
 866	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode) ||
 867	    ext4_test_inode_flag(inode, EXT4_INODE_EA_INODE))
 868		flags |= EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_METADATA;
 869	else if (ext4_should_journal_data(inode))
 870		flags |= EXT4_FREE_BLOCKS_FORGET;
 871
 872	if (!ext4_inode_block_valid(inode, block_to_free, count)) {
 873		EXT4_ERROR_INODE(inode, "attempt to clear invalid "
 874				 "blocks %llu len %lu",
 875				 (unsigned long long) block_to_free, count);
 876		return 1;
 877	}
 878
 879	err = ext4_ind_truncate_ensure_credits(handle, inode, bh,
 880				ext4_free_data_revoke_credits(inode, count));
 881	if (err < 0)
 882		goto out_err;
 883
 884	for (p = first; p < last; p++)
 885		*p = 0;
 886
 887	ext4_free_blocks(handle, inode, NULL, block_to_free, count, flags);
 888	return 0;
 889out_err:
 890	ext4_std_error(inode->i_sb, err);
 891	return err;
 892}
 893
 894/**
 895 * ext4_free_data - free a list of data blocks
 896 * @handle:	handle for this transaction
 897 * @inode:	inode we are dealing with
 898 * @this_bh:	indirect buffer_head which contains *@first and *@last
 899 * @first:	array of block numbers
 900 * @last:	points immediately past the end of array
 901 *
 902 * We are freeing all blocks referred from that array (numbers are stored as
 903 * little-endian 32-bit) and updating @inode->i_blocks appropriately.
 904 *
 905 * We accumulate contiguous runs of blocks to free.  Conveniently, if these
 906 * blocks are contiguous then releasing them at one time will only affect one
 907 * or two bitmap blocks (+ group descriptor(s) and superblock) and we won't
 908 * actually use a lot of journal space.
 909 *
 910 * @this_bh will be %NULL if @first and @last point into the inode's direct
 911 * block pointers.
 912 */
 913static void ext4_free_data(handle_t *handle, struct inode *inode,
 914			   struct buffer_head *this_bh,
 915			   __le32 *first, __le32 *last)
 916{
 917	ext4_fsblk_t block_to_free = 0;    /* Starting block # of a run */
 918	unsigned long count = 0;	    /* Number of blocks in the run */
 919	__le32 *block_to_free_p = NULL;	    /* Pointer into inode/ind
 920					       corresponding to
 921					       block_to_free */
 922	ext4_fsblk_t nr;		    /* Current block # */
 923	__le32 *p;			    /* Pointer into inode/ind
 924					       for current block */
 925	int err = 0;
 926
 927	if (this_bh) {				/* For indirect block */
 928		BUFFER_TRACE(this_bh, "get_write_access");
 929		err = ext4_journal_get_write_access(handle, inode->i_sb,
 930						    this_bh, EXT4_JTR_NONE);
 931		/* Important: if we can't update the indirect pointers
 932		 * to the blocks, we can't free them. */
 933		if (err)
 934			return;
 935	}
 936
 937	for (p = first; p < last; p++) {
 938		nr = le32_to_cpu(*p);
 939		if (nr) {
 940			/* accumulate blocks to free if they're contiguous */
 941			if (count == 0) {
 942				block_to_free = nr;
 943				block_to_free_p = p;
 944				count = 1;
 945			} else if (nr == block_to_free + count) {
 946				count++;
 947			} else {
 948				err = ext4_clear_blocks(handle, inode, this_bh,
 949						        block_to_free, count,
 950						        block_to_free_p, p);
 951				if (err)
 952					break;
 953				block_to_free = nr;
 954				block_to_free_p = p;
 955				count = 1;
 956			}
 957		}
 958	}
 959
 960	if (!err && count > 0)
 961		err = ext4_clear_blocks(handle, inode, this_bh, block_to_free,
 962					count, block_to_free_p, p);
 963	if (err < 0)
 964		/* fatal error */
 965		return;
 966
 967	if (this_bh) {
 968		BUFFER_TRACE(this_bh, "call ext4_handle_dirty_metadata");
 969
 970		/*
 971		 * The buffer head should have an attached journal head at this
 972		 * point. However, if the data is corrupted and an indirect
 973		 * block pointed to itself, it would have been detached when
 974		 * the block was cleared. Check for this instead of OOPSing.
 975		 */
 976		if ((EXT4_JOURNAL(inode) == NULL) || bh2jh(this_bh))
 977			ext4_handle_dirty_metadata(handle, inode, this_bh);
 978		else
 979			EXT4_ERROR_INODE(inode,
 980					 "circular indirect block detected at "
 981					 "block %llu",
 982				(unsigned long long) this_bh->b_blocknr);
 983	}
 984}
 985
 986/**
 987 *	ext4_free_branches - free an array of branches
 988 *	@handle: JBD handle for this transaction
 989 *	@inode:	inode we are dealing with
 990 *	@parent_bh: the buffer_head which contains *@first and *@last
 991 *	@first:	array of block numbers
 992 *	@last:	pointer immediately past the end of array
 993 *	@depth:	depth of the branches to free
 994 *
 995 *	We are freeing all blocks referred from these branches (numbers are
 996 *	stored as little-endian 32-bit) and updating @inode->i_blocks
 997 *	appropriately.
 998 */
 999static void ext4_free_branches(handle_t *handle, struct inode *inode,
1000			       struct buffer_head *parent_bh,
1001			       __le32 *first, __le32 *last, int depth)
1002{
1003	ext4_fsblk_t nr;
1004	__le32 *p;
1005
1006	if (ext4_handle_is_aborted(handle))
1007		return;
1008
1009	if (depth--) {
1010		struct buffer_head *bh;
1011		int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1012		p = last;
1013		while (--p >= first) {
1014			nr = le32_to_cpu(*p);
1015			if (!nr)
1016				continue;		/* A hole */
1017
1018			if (!ext4_inode_block_valid(inode, nr, 1)) {
1019				EXT4_ERROR_INODE(inode,
1020						 "invalid indirect mapped "
1021						 "block %lu (level %d)",
1022						 (unsigned long) nr, depth);
1023				break;
1024			}
1025
1026			/* Go read the buffer for the next level down */
1027			bh = ext4_sb_bread(inode->i_sb, nr, 0);
1028
1029			/*
1030			 * A read failure? Report error and clear slot
1031			 * (should be rare).
1032			 */
1033			if (IS_ERR(bh)) {
1034				ext4_error_inode_block(inode, nr, -PTR_ERR(bh),
1035						       "Read failure");
1036				continue;
1037			}
1038
1039			/* This zaps the entire block.  Bottom up. */
1040			BUFFER_TRACE(bh, "free child branches");
1041			ext4_free_branches(handle, inode, bh,
1042					(__le32 *) bh->b_data,
1043					(__le32 *) bh->b_data + addr_per_block,
1044					depth);
1045			brelse(bh);
1046
1047			/*
1048			 * Everything below this pointer has been
1049			 * released.  Now let this top-of-subtree go.
1050			 *
1051			 * We want the freeing of this indirect block to be
1052			 * atomic in the journal with the updating of the
1053			 * bitmap block which owns it.  So make some room in
1054			 * the journal.
1055			 *
1056			 * We zero the parent pointer *after* freeing its
1057			 * pointee in the bitmaps, so if extend_transaction()
1058			 * for some reason fails to put the bitmap changes and
1059			 * the release into the same transaction, recovery
1060			 * will merely complain about releasing a free block,
1061			 * rather than leaking blocks.
1062			 */
1063			if (ext4_handle_is_aborted(handle))
1064				return;
1065			if (ext4_ind_truncate_ensure_credits(handle, inode,
1066					NULL,
1067					ext4_free_metadata_revoke_credits(
1068							inode->i_sb, 1)) < 0)
1069				return;
1070
1071			/*
1072			 * The forget flag here is critical because if
1073			 * we are journaling (and not doing data
1074			 * journaling), we have to make sure a revoke
1075			 * record is written to prevent the journal
1076			 * replay from overwriting the (former)
1077			 * indirect block if it gets reallocated as a
1078			 * data block.  This must happen in the same
1079			 * transaction where the data blocks are
1080			 * actually freed.
1081			 */
1082			ext4_free_blocks(handle, inode, NULL, nr, 1,
1083					 EXT4_FREE_BLOCKS_METADATA|
1084					 EXT4_FREE_BLOCKS_FORGET);
1085
1086			if (parent_bh) {
1087				/*
1088				 * The block which we have just freed is
1089				 * pointed to by an indirect block: journal it
1090				 */
1091				BUFFER_TRACE(parent_bh, "get_write_access");
1092				if (!ext4_journal_get_write_access(handle,
1093						inode->i_sb, parent_bh,
1094						EXT4_JTR_NONE)) {
1095					*p = 0;
1096					BUFFER_TRACE(parent_bh,
1097					"call ext4_handle_dirty_metadata");
1098					ext4_handle_dirty_metadata(handle,
1099								   inode,
1100								   parent_bh);
1101				}
1102			}
1103		}
1104	} else {
1105		/* We have reached the bottom of the tree. */
1106		BUFFER_TRACE(parent_bh, "free data blocks");
1107		ext4_free_data(handle, inode, parent_bh, first, last);
1108	}
1109}
1110
1111void ext4_ind_truncate(handle_t *handle, struct inode *inode)
1112{
1113	struct ext4_inode_info *ei = EXT4_I(inode);
1114	__le32 *i_data = ei->i_data;
1115	int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1116	ext4_lblk_t offsets[4];
1117	Indirect chain[4];
1118	Indirect *partial;
1119	__le32 nr = 0;
1120	int n = 0;
1121	ext4_lblk_t last_block, max_block;
1122	unsigned blocksize = inode->i_sb->s_blocksize;
1123
1124	last_block = (inode->i_size + blocksize-1)
1125					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1126	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1127					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1128
1129	if (last_block != max_block) {
1130		n = ext4_block_to_path(inode, last_block, offsets, NULL);
1131		if (n == 0)
1132			return;
1133	}
1134
1135	ext4_es_remove_extent(inode, last_block, EXT_MAX_BLOCKS - last_block);
1136
1137	/*
1138	 * The orphan list entry will now protect us from any crash which
1139	 * occurs before the truncate completes, so it is now safe to propagate
1140	 * the new, shorter inode size (held for now in i_size) into the
1141	 * on-disk inode. We do this via i_disksize, which is the value which
1142	 * ext4 *really* writes onto the disk inode.
1143	 */
1144	ei->i_disksize = inode->i_size;
1145
1146	if (last_block == max_block) {
1147		/*
1148		 * It is unnecessary to free any data blocks if last_block is
1149		 * equal to the indirect block limit.
1150		 */
1151		return;
1152	} else if (n == 1) {		/* direct blocks */
1153		ext4_free_data(handle, inode, NULL, i_data+offsets[0],
1154			       i_data + EXT4_NDIR_BLOCKS);
1155		goto do_indirects;
1156	}
1157
1158	partial = ext4_find_shared(inode, n, offsets, chain, &nr);
1159	/* Kill the top of shared branch (not detached) */
1160	if (nr) {
1161		if (partial == chain) {
1162			/* Shared branch grows from the inode */
1163			ext4_free_branches(handle, inode, NULL,
1164					   &nr, &nr+1, (chain+n-1) - partial);
1165			*partial->p = 0;
1166			/*
1167			 * We mark the inode dirty prior to restart,
1168			 * and prior to stop.  No need for it here.
1169			 */
1170		} else {
1171			/* Shared branch grows from an indirect block */
1172			BUFFER_TRACE(partial->bh, "get_write_access");
1173			ext4_free_branches(handle, inode, partial->bh,
1174					partial->p,
1175					partial->p+1, (chain+n-1) - partial);
1176		}
1177	}
1178	/* Clear the ends of indirect blocks on the shared branch */
1179	while (partial > chain) {
1180		ext4_free_branches(handle, inode, partial->bh, partial->p + 1,
1181				   (__le32*)partial->bh->b_data+addr_per_block,
1182				   (chain+n-1) - partial);
1183		BUFFER_TRACE(partial->bh, "call brelse");
1184		brelse(partial->bh);
1185		partial--;
1186	}
1187do_indirects:
1188	/* Kill the remaining (whole) subtrees */
1189	switch (offsets[0]) {
1190	default:
1191		nr = i_data[EXT4_IND_BLOCK];
1192		if (nr) {
1193			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1194			i_data[EXT4_IND_BLOCK] = 0;
1195		}
1196		fallthrough;
1197	case EXT4_IND_BLOCK:
1198		nr = i_data[EXT4_DIND_BLOCK];
1199		if (nr) {
1200			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1201			i_data[EXT4_DIND_BLOCK] = 0;
1202		}
1203		fallthrough;
1204	case EXT4_DIND_BLOCK:
1205		nr = i_data[EXT4_TIND_BLOCK];
1206		if (nr) {
1207			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1208			i_data[EXT4_TIND_BLOCK] = 0;
1209		}
1210		fallthrough;
1211	case EXT4_TIND_BLOCK:
1212		;
1213	}
1214}
1215
1216/**
1217 *	ext4_ind_remove_space - remove space from the range
1218 *	@handle: JBD handle for this transaction
1219 *	@inode:	inode we are dealing with
1220 *	@start:	First block to remove
1221 *	@end:	One block after the last block to remove (exclusive)
1222 *
1223 *	Free the blocks in the defined range (end is exclusive endpoint of
1224 *	range). This is used by ext4_punch_hole().
1225 */
1226int ext4_ind_remove_space(handle_t *handle, struct inode *inode,
1227			  ext4_lblk_t start, ext4_lblk_t end)
1228{
1229	struct ext4_inode_info *ei = EXT4_I(inode);
1230	__le32 *i_data = ei->i_data;
1231	int addr_per_block = EXT4_ADDR_PER_BLOCK(inode->i_sb);
1232	ext4_lblk_t offsets[4], offsets2[4];
1233	Indirect chain[4], chain2[4];
1234	Indirect *partial, *partial2;
1235	Indirect *p = NULL, *p2 = NULL;
1236	ext4_lblk_t max_block;
1237	__le32 nr = 0, nr2 = 0;
1238	int n = 0, n2 = 0;
1239	unsigned blocksize = inode->i_sb->s_blocksize;
1240
1241	max_block = (EXT4_SB(inode->i_sb)->s_bitmap_maxbytes + blocksize-1)
1242					>> EXT4_BLOCK_SIZE_BITS(inode->i_sb);
1243	if (end >= max_block)
1244		end = max_block;
1245	if ((start >= end) || (start > max_block))
1246		return 0;
1247
1248	n = ext4_block_to_path(inode, start, offsets, NULL);
1249	n2 = ext4_block_to_path(inode, end, offsets2, NULL);
1250
1251	BUG_ON(n > n2);
1252
1253	if ((n == 1) && (n == n2)) {
1254		/* We're punching only within direct block range */
1255		ext4_free_data(handle, inode, NULL, i_data + offsets[0],
1256			       i_data + offsets2[0]);
1257		return 0;
1258	} else if (n2 > n) {
1259		/*
1260		 * Start and end are on a different levels so we're going to
1261		 * free partial block at start, and partial block at end of
1262		 * the range. If there are some levels in between then
1263		 * do_indirects label will take care of that.
1264		 */
1265
1266		if (n == 1) {
1267			/*
1268			 * Start is at the direct block level, free
1269			 * everything to the end of the level.
1270			 */
1271			ext4_free_data(handle, inode, NULL, i_data + offsets[0],
1272				       i_data + EXT4_NDIR_BLOCKS);
1273			goto end_range;
1274		}
1275
1276
1277		partial = p = ext4_find_shared(inode, n, offsets, chain, &nr);
1278		if (nr) {
1279			if (partial == chain) {
1280				/* Shared branch grows from the inode */
1281				ext4_free_branches(handle, inode, NULL,
1282					   &nr, &nr+1, (chain+n-1) - partial);
1283				*partial->p = 0;
1284			} else {
1285				/* Shared branch grows from an indirect block */
1286				BUFFER_TRACE(partial->bh, "get_write_access");
1287				ext4_free_branches(handle, inode, partial->bh,
1288					partial->p,
1289					partial->p+1, (chain+n-1) - partial);
1290			}
1291		}
1292
1293		/*
1294		 * Clear the ends of indirect blocks on the shared branch
1295		 * at the start of the range
1296		 */
1297		while (partial > chain) {
1298			ext4_free_branches(handle, inode, partial->bh,
1299				partial->p + 1,
1300				(__le32 *)partial->bh->b_data+addr_per_block,
1301				(chain+n-1) - partial);
1302			partial--;
1303		}
1304
1305end_range:
1306		partial2 = p2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
1307		if (nr2) {
1308			if (partial2 == chain2) {
1309				/*
1310				 * Remember, end is exclusive so here we're at
1311				 * the start of the next level we're not going
1312				 * to free. Everything was covered by the start
1313				 * of the range.
1314				 */
1315				goto do_indirects;
1316			}
1317		} else {
1318			/*
1319			 * ext4_find_shared returns Indirect structure which
1320			 * points to the last element which should not be
1321			 * removed by truncate. But this is end of the range
1322			 * in punch_hole so we need to point to the next element
1323			 */
1324			partial2->p++;
1325		}
1326
1327		/*
1328		 * Clear the ends of indirect blocks on the shared branch
1329		 * at the end of the range
1330		 */
1331		while (partial2 > chain2) {
1332			ext4_free_branches(handle, inode, partial2->bh,
1333					   (__le32 *)partial2->bh->b_data,
1334					   partial2->p,
1335					   (chain2+n2-1) - partial2);
1336			partial2--;
1337		}
1338		goto do_indirects;
1339	}
1340
1341	/* Punch happened within the same level (n == n2) */
1342	partial = p = ext4_find_shared(inode, n, offsets, chain, &nr);
1343	partial2 = p2 = ext4_find_shared(inode, n2, offsets2, chain2, &nr2);
1344
1345	/* Free top, but only if partial2 isn't its subtree. */
1346	if (nr) {
1347		int level = min(partial - chain, partial2 - chain2);
1348		int i;
1349		int subtree = 1;
1350
1351		for (i = 0; i <= level; i++) {
1352			if (offsets[i] != offsets2[i]) {
1353				subtree = 0;
1354				break;
1355			}
1356		}
1357
1358		if (!subtree) {
1359			if (partial == chain) {
1360				/* Shared branch grows from the inode */
1361				ext4_free_branches(handle, inode, NULL,
1362						   &nr, &nr+1,
1363						   (chain+n-1) - partial);
1364				*partial->p = 0;
1365			} else {
1366				/* Shared branch grows from an indirect block */
1367				BUFFER_TRACE(partial->bh, "get_write_access");
1368				ext4_free_branches(handle, inode, partial->bh,
1369						   partial->p,
1370						   partial->p+1,
1371						   (chain+n-1) - partial);
1372			}
1373		}
1374	}
1375
1376	if (!nr2) {
1377		/*
1378		 * ext4_find_shared returns Indirect structure which
1379		 * points to the last element which should not be
1380		 * removed by truncate. But this is end of the range
1381		 * in punch_hole so we need to point to the next element
1382		 */
1383		partial2->p++;
1384	}
1385
1386	while (partial > chain || partial2 > chain2) {
1387		int depth = (chain+n-1) - partial;
1388		int depth2 = (chain2+n2-1) - partial2;
1389
1390		if (partial > chain && partial2 > chain2 &&
1391		    partial->bh->b_blocknr == partial2->bh->b_blocknr) {
1392			/*
1393			 * We've converged on the same block. Clear the range,
1394			 * then we're done.
1395			 */
1396			ext4_free_branches(handle, inode, partial->bh,
1397					   partial->p + 1,
1398					   partial2->p,
1399					   (chain+n-1) - partial);
1400			goto cleanup;
1401		}
1402
1403		/*
1404		 * The start and end partial branches may not be at the same
1405		 * level even though the punch happened within one level. So, we
1406		 * give them a chance to arrive at the same level, then walk
1407		 * them in step with each other until we converge on the same
1408		 * block.
1409		 */
1410		if (partial > chain && depth <= depth2) {
1411			ext4_free_branches(handle, inode, partial->bh,
1412					   partial->p + 1,
1413					   (__le32 *)partial->bh->b_data+addr_per_block,
1414					   (chain+n-1) - partial);
1415			partial--;
1416		}
1417		if (partial2 > chain2 && depth2 <= depth) {
1418			ext4_free_branches(handle, inode, partial2->bh,
1419					   (__le32 *)partial2->bh->b_data,
1420					   partial2->p,
1421					   (chain2+n2-1) - partial2);
1422			partial2--;
1423		}
1424	}
1425
1426cleanup:
1427	while (p && p > chain) {
1428		BUFFER_TRACE(p->bh, "call brelse");
1429		brelse(p->bh);
1430		p--;
1431	}
1432	while (p2 && p2 > chain2) {
1433		BUFFER_TRACE(p2->bh, "call brelse");
1434		brelse(p2->bh);
1435		p2--;
1436	}
1437	return 0;
1438
1439do_indirects:
1440	/* Kill the remaining (whole) subtrees */
1441	switch (offsets[0]) {
1442	default:
1443		if (++n >= n2)
1444			break;
1445		nr = i_data[EXT4_IND_BLOCK];
1446		if (nr) {
1447			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 1);
1448			i_data[EXT4_IND_BLOCK] = 0;
1449		}
1450		fallthrough;
1451	case EXT4_IND_BLOCK:
1452		if (++n >= n2)
1453			break;
1454		nr = i_data[EXT4_DIND_BLOCK];
1455		if (nr) {
1456			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 2);
1457			i_data[EXT4_DIND_BLOCK] = 0;
1458		}
1459		fallthrough;
1460	case EXT4_DIND_BLOCK:
1461		if (++n >= n2)
1462			break;
1463		nr = i_data[EXT4_TIND_BLOCK];
1464		if (nr) {
1465			ext4_free_branches(handle, inode, NULL, &nr, &nr+1, 3);
1466			i_data[EXT4_TIND_BLOCK] = 0;
1467		}
1468		fallthrough;
1469	case EXT4_TIND_BLOCK:
1470		;
1471	}
1472	goto cleanup;
1473}