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Release 4.10 fs/ext4/indirect.c

Directory: fs/ext4
/*
 *  linux/fs/ext4/indirect.c
 *
 *  from
 *
 *  linux/fs/ext4/inode.c
 *
 * Copyright (C) 1992, 1993, 1994, 1995
 * Remy Card (card@masi.ibp.fr)
 * Laboratoire MASI - Institut Blaise Pascal
 * Universite Pierre et Marie Curie (Paris VI)
 *
 *  from
 *
 *  linux/fs/minix/inode.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 *  Goal-directed block allocation by Stephen Tweedie
 *      (sct@redhat.com), 1993, 1998
 */

#include "ext4_jbd2.h"
#include "truncate.h"
#include <linux/dax.h>
#include <linux/uio.h>

#include <trace/events/ext4.h>

typedef struct {
	
__le32	*p;
	
__le32	key;
	
struct buffer_head *bh;
} 
Indirect;




static inline void add_chain(Indirect *p, struct buffer_head *bh, __le32 *v)
{
	p->key = *(p->p = v);
	p->bh = bh;
}


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/**
 *      ext4_block_to_path - parse the block number into array of offsets
 *      @inode: inode in question (we are only interested in its superblock)
 *      @i_block: block number to be parsed
 *      @offsets: array to store the offsets in
 *      @boundary: set this non-zero if the referred-to block is likely to be
 *             followed (on disk) by an indirect block.
 *
 *      To store the locations of file's data ext4 uses a data structure common
 *      for UNIX filesystems - tree of pointers anchored in the inode, with
 *      data blocks at leaves and indirect blocks in intermediate nodes.
 *      This function translates the block number into path in that tree -
 *      return value is the path length and @offsets[n] is the offset of
 *      pointer to (n+1)th node in the nth one. If @block is out of range
 *      (negative or too large) warning is printed and zero returned.
 *
 *      Note: function doesn't find node addresses, so no IO is needed. All
 *      we need to know is the capacity of indirect blocks (taken from the
 *      inode->i_sb).
 */

/*
 * Portability note: the last comparison (check that we fit into triple
 * indirect block) is spelled differently, because otherwise on an
 * architecture with 32-bit longs and 8Kb pages we might get into trouble
 * if our filesystem had 8Kb blocks. We might use long long, but that would
 * kill us on x86. Oh, well, at least the sign propagation does not matter -
 * i_block would have to be negative in the very beginning, so we would not
 * get there at all.
 */




static int ext4_block_to_path(struct inode *inode,
			      ext4_lblk_t i_block,
			      ext4_lblk_t offsets[4], int *boundary)
{
	int ptrs = EXT4_ADDR_PER_BLOCK(inode->i_sb);
	int ptrs_bits = EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb);
	const long direct_blocks = EXT4_NDIR_BLOCKS,
		indirect_blocks = ptrs,
		double_blocks = (1 << (ptrs_bits * 2));
	int n = 0;
	int final = 0;

	if (i_block < direct_blocks) {
		offsets[n++] = i_block;
		final = direct_blocks;
	} else if ((i_block -= direct_blocks) < indirect_blocks) {
		offsets[n++] = EXT4_IND_BLOCK;
		offsets[n++] = i_block;
		final = ptrs;
	} else if ((i_block -= indirect_blocks) < double_blocks) {
		offsets[n++] = EXT4_DIND_BLOCK;
		offsets[n++] = i_block >> ptrs_bits;
		offsets[n++] = i_block & (ptrs - 1);
		final = ptrs;
	} else if (((i_block -= double_blocks) >> (ptrs_bits * 2)) < ptrs) {
		offsets[n++] = EXT4_TIND_BLOCK;
		offsets[n++] = i_block >> (ptrs_bits * 2);
		offsets[n++] = (i_block >> ptrs_bits) & (ptrs - 1);
		offsets[n++] = i_block & (ptrs - 1);
		final = ptrs;
	} else {
		ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
			     i_block + direct_blocks +
			     indirect_blocks + double_blocks, inode->i_ino);
	}
	if (boundary)
		*boundary = final - 1 - (i_block & (ptrs - 1));
	return n;
}


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/**
 *      ext4_get_branch - read the chain of indirect blocks leading to data
 *      @inode: inode in question
 *      @depth: depth of the chain (1 - direct pointer, etc.)
 *      @offsets: offsets of pointers in inode/indirect blocks
 *      @chain: place to store the result
 *      @err: here we store the error value
 *
 *      Function fills the array of triples <key, p, bh> and returns %NULL
 *      if everything went OK or the pointer to the last filled triple
 *      (incomplete one) otherwise. Upon the return chain[i].key contains
 *      the number of (i+1)-th block in the chain (as it is stored in memory,
 *      i.e. little-endian 32-bit), chain[i].p contains the address of that
 *      number (it points into struct inode for i==0 and into the bh->b_data
 *      for i>0) and chain[i].bh points to the buffer_head of i-th indirect
 *      block for i>0 and NULL for i==0. In other words, it holds the block
 *      numbers of the chain, addresses they were taken from (and where we can
 *      verify that chain did not change) and buffer_heads hosting these
 *      numbers.
 *
 *      Function stops when it stumbles upon zero pointer (absent block)
 *              (pointer to last triple returned, *@err == 0)
 *      or when it gets an IO error reading an indirect block
 *              (ditto, *@err == -EIO)
 *      or when it reads all @depth-1 indirect blocks successfully and finds
 *      the whole chain, all way to the data (returns %NULL, *err == 0).
 *
 *      Need to be called with
 *      down_read(&EXT4_I(inode)->i_data_sem)
 */



static Indirect *ext4_get_branch(struct inode *inode, int depth,
				 ext4_lblk_t  *offsets,
				 Indirect chain[4], int *err)
{
	struct super_block *sb = inode->i_sb;
	Indirect *p = chain;
	struct buffer_head *bh;
	int ret = -EIO;

	*err = 0;
	/* i_data is not going away, no lock needed */
	add_chain(chain, NULL, EXT4_I(inode)->i_data + *offsets);
	if (!p->key)
		goto no_block;
	while (--depth) {
		bh = sb_getblk(sb, le32_to_cpu(p->key));
		if (unlikely(!bh)) {
			ret = -ENOMEM;
			goto failure;
		}

		if (!bh_uptodate_or_lock(bh)) {
			if (bh_submit_read(bh) < 0) {
				put_bh(bh);
				goto failure;
			}
			/* validate block references */
			if (ext4_check_indirect_blockref(inode, bh)) {
				put_bh(bh);
				goto failure;
			}
		}

		add_chain(++p, bh, (__le32 *)bh->b_data + *++offsets);
		/* Reader: end */
		if (!p->key)
			goto no_block;
	}
	return NULL;

failure:
	*err = ret;
no_block:
	return p;
}


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/**
 *      ext4_find_near - find a place for allocation with sufficient locality
 *      @inode: owner
 *      @ind: descriptor of indirect block.
 *
 *      This function returns the preferred place for block allocation.
 *      It is used when heuristic for sequential allocation fails.
 *      Rules are:
 *        + if there is a block to the left of our position - allocate near it.
 *        + if pointer will live in indirect block - allocate near that block.
 *        + if pointer will live in inode - allocate in the same
 *          cylinder group.
 *
 * In the latter case we colour the starting block by the callers PID to
 * prevent it from clashing with concurrent allocations for a different inode
 * in the same block group.   The PID is used here so that functionally related
 * files will be close-by on-disk.
 *
 *      Caller must make sure that @ind is valid and will stay that way.
 */



static ext4_fsblk_t ext4_find_near(struct inode *inode, Indirect *ind)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	__le32 *start = ind->bh ? (__le32 *) ind->bh->b_data : ei->i_data;
	__le32 *p;

	/* Try to find previous block */
	for (p = ind->p - 1; p >= start; p--) {
		if (*p)
			return le32_to_cpu(*p);
	}

	/* No such thing, so let's try location of indirect block */
	if (ind->bh)
		return ind->bh->b_blocknr;

	/*
         * It is going to be referred to from the inode itself? OK, just put it
         * into the same cylinder group then.
         */
	return ext4_inode_to_goal_block(inode);
}


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/**
 *      ext4_find_goal - find a preferred place for allocation.
 *      @inode: owner
 *      @block:  block we want
 *      @partial: pointer to the last triple within a chain
 *
 *      Normally this function find the preferred place for block allocation,
 *      returns it.
 *      Because this is only used for non-extent files, we limit the block nr
 *      to 32 bits.
 */



static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
				   Indirect *partial)
{
	ext4_fsblk_t goal;

	/*
         * XXX need to get goal block from mballoc's data structures
         */

	goal = ext4_find_near(inode, partial);
	goal = goal & EXT4_MAX_BLOCK_FILE_PHYS;
	return goal;
}


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/**
 *      ext4_blks_to_allocate - Look up the block map and count the number
 *      of direct blocks need to be allocated for the given branch.
 *
 *      @branch: chain of indirect blocks
 *      @k: number of blocks need for indirect blocks
 *      @blks: number of data blocks to be mapped.
 *      @blocks_to_boundary:  the offset in the indirect block
 *
 *      return the total number of blocks to be allocate, including the
 *      direct and indirect blocks.
 */



static int ext4_blks_to_allocate(Indirect *branch, int k, unsigned int blks,
				 int blocks_to_boundary)
{
	unsigned int count = 0;

	/*
         * Simple case, [t,d]Indirect block(s) has not allocated yet
         * then it's clear blocks on that path have not allocated
         */
	if (k > 0) {
		/* right now we don't handle cross boundary allocation */
		if (blks < blocks_to_boundary + 1)
			count += blks;
		else
			count += blocks_to_boundary + 1;
		return count;
	}

	count++;
	while (count < blks && count <= blocks_to_boundary &&
		le32_to_cpu(*(branch[0].p + count)) == 0) {
		count++;
	}
	return count;
}


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/**
 *      ext4_alloc_branch - allocate and set up a chain of blocks.
 *      @handle: handle for this transaction
 *      @inode: owner
 *      @indirect_blks: number of allocated indirect blocks
 *      @blks: number of allocated direct blocks
 *      @goal: preferred place for allocation
 *      @offsets: offsets (in the blocks) to store the pointers to next.
 *      @branch: place to store the chain in.
 *
 *      This function allocates blocks, zeroes out all but the last one,
 *      links them into chain and (if we are synchronous) writes them to disk.
 *      In other words, it prepares a branch that can be spliced onto the
 *      inode. It stores the information about that chain in the branch[], in
 *      the same format as ext4_get_branch() would do. We are calling it after
 *      we had read the existing part of chain and partial points to the last
 *      triple of that (one with zero ->key). Upon the exit we have the same
 *      picture as after the successful ext4_get_block(), except that in one
 *      place chain is disconnected - *branch->p is still zero (we did not
 *      set the last link), but branch->key contains the number that should
 *      be placed into *branch->p to fill that gap.
 *
 *      If allocation fails we free all blocks we've allocated (and forget
 *      their buffer_heads) and return the error value the from failed
 *      ext4_alloc_block() (normally -ENOSPC). Otherwise we set the chain
 *      as described above and return 0.
 */



static int ext4_alloc_branch(handle_t *handle,
			     struct ext4_allocation_request *ar,
			     int indirect_blks, ext4_lblk_t *offsets,
			     Indirect *branch)
{
	struct buffer_head *		bh;
	ext4_fsblk_t			b, new_blocks[4];
	__le32				*p;
	int				i, j, err, len = 1;

	for (i = 0; i <= indirect_blks; i++) {
		if (i == indirect_blks) {
			new_blocks[i] = ext4_mb_new_blocks(handle, ar, &err);
		} else
			ar->goal = new_blocks[i] = ext4_new_meta_blocks(handle,
					ar->inode, ar->goal,
					ar->flags & EXT4_MB_DELALLOC_RESERVED,
					NULL, &err);
		if (err) {
			i--;
			goto failed;
		}
		branch[i].key = cpu_to_le32(new_blocks[i]);
		if (i == 0)
			continue;

		bh = branch[i].bh = sb_getblk(ar->inode->i_sb, new_blocks[i-1]);
		if (unlikely(!bh)) {
			err = -ENOMEM;
			goto failed;
		}
		lock_buffer(bh);
		BUFFER_TRACE(bh, "call get_create_access");
		err = ext4_journal_get_create_access(handle, bh);
		if (err) {
			unlock_buffer(bh);
			goto failed;
		}

		memset(bh->b_data, 0, bh->b_size);
		p = branch[i].p = (__le32 *) bh->b_data + offsets[i];
		b = new_blocks[i];

		if (i == indirect_blks)
			len = ar->len;
		for (j = 0; j < len; j++)
			*p++ = cpu_to_le32(b++);

		BUFFER_TRACE(bh, "marking uptodate");
		set_buffer_uptodate(bh);
		unlock_buffer(bh);

		BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
		err = ext4_handle_dirty_metadata(handle, ar->inode, bh);
		if (err)
			goto failed;
	}
	return 0;
failed:
	for (; i >= 0; i--) {
		/*
                 * We want to ext4_forget() only freshly allocated indirect
                 * blocks.  Buffer for new_blocks[i-1] is at branch[i].bh and
                 * buffer at branch[0].bh is indirect block / inode already
                 * existing before ext4_alloc_branch() was called.
                 */
		if (i > 0 && i != indirect_blks && branch[i].bh)
			ext4_forget(handle, 1, ar->inode, branch[i].bh,
				    branch[i].bh->b_blocknr);
		ext4_free_blocks(handle, ar->inode, NULL, new_blocks[i],
				 (i == indirect_blks) ? ar->len : 1, 0);
	}
	return err;
}


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/**
 * ext4_splice_branch - splice the allocated branch onto inode.
 * @handle: handle for this transaction
 * @inode: owner
 * @block: (logical) number of block we are adding
 * @chain: chain of indirect blocks (with a missing link - see
 *      ext4_alloc_branch)
 * @where: location of missing link
 * @num:   number of indirect blocks we are adding
 * @blks:  number of direct blocks we are adding
 *
 * This function fills the missing link and does all housekeeping needed in
 * inode (->i_blocks, etc.). In case of success we end up with the full
 * chain to new block and return 0.
 */



static int ext4_splice_branch(handle_t *handle,
			      struct ext4_allocation_request *ar,
			      Indirect *where, int num)
{
	int i;
	int err = 0;
	ext4_fsblk_t current_block;

	/*
         * If we're splicing into a [td]indirect block (as opposed to the
         * inode) then we need to get write access to the [td]indirect block
         * before the splice.
         */
	if (where->bh) {
		BUFFER_TRACE(where->bh, "get_write_access");
		err = ext4_journal_get_write_access(handle, where->bh);
		if (err)
			goto err_out;
	}
	/* That's it */

	*where->p = where->key;

	/*
         * Update the host buffer_head or inode to point to more just allocated
         * direct blocks blocks
         */
	if (num == 0 && ar->len > 1) {
		current_block = le32_to_cpu(where->key) + 1;
		for (i = 1; i < ar->len; i++)
			*(where->p + i) = cpu_to_le32(current_block++);
	}

	/* We are done with atomic stuff, now do the rest of housekeeping */
	/* had we spliced it onto indirect block? */
	if (where->bh) {
		/*
                 * If we spliced it onto an indirect block, we haven't
                 * altered the inode.  Note however that if it is being spliced
                 * onto an indirect block at the very end of the file (the
                 * file is growing) then we *will* alter the inode to reflect
                 * the new i_size.  But that is not done here - it is done in
                 * generic_commit_write->__mark_inode_dirty->ext4_dirty_inode.
                 */
		jbd_debug(5, "splicing indirect only\n");
		BUFFER_TRACE(where->bh, "call ext4_handle_dirty_metadata");
		err = ext4_handle_dirty_metadata(handle, ar->inode, where->bh);
		if (err)
			goto err_out;
	} else {
		/*
                 * OK, we spliced it into the inode itself on a direct block.
                 */
		ext4_mark_inode_dirty(handle, ar->inode);
		jbd_debug(5, "splicing direct\n");
	}
	return err;

err_out:
	for (i = 1; i <= num; i++) {
		/*
                 * branch[i].bh is newly allocated, so there is no
                 * need to revoke the block, which is why we don't
                 * need to set EXT4_FREE_BLOCKS_METADATA.
                 */
		ext4_free_blocks(handle, ar->inode, where[i].bh, 0, 1,
				 EXT4_FREE_BLOCKS_FORGET);
	}
	ext4_free_blocks(handle, ar->inode, NULL, le32_to_cpu(where[num].key),
			 ar->len, 0);

	return err;
}


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/*
 * The ext4_ind_map_blocks() function handles non-extents inodes
 * (i.e., using the traditional indirect/double-indirect i_blocks
 * scheme) for ext4_map_blocks().
 *
 * Allocation strategy is simple: if we have to allocate something, we will
 * have to go the whole way to leaf. So let's do it before attaching anything
 * to tree, set linkage between the newborn blocks, write them if sync is
 * required, recheck the path, free and repeat if check fails, otherwise
 * set the last missing link (that will protect us from any truncate-generated
 * removals - all blocks on the path are immune now) and possibly force the
 * write on the parent block.
 * That has a nice additional property: no special recovery from the failed
 * allocations is needed - we simply release blocks and do not touch anything
 * reachable from inode.
 *
 * `handle' can be NULL if create == 0.
 *
 * return > 0, # of blocks mapped or allocated.
 * return = 0, if plain lookup failed.
 * return < 0, error case.
 *
 * The ext4_ind_get_blocks() function should be called with
 * down_write(&EXT4_I(inode)->i_data_sem) if allocating filesystem
 * blocks (i.e., flags has EXT4_GET_BLOCKS_CREATE set) or
 * down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system
 * blocks.
 */



int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
			struct ext4_map_blocks *map,
			int flags)
{
	struct ext4_allocation_request ar;
	int err = -EIO;
	ext4_lblk_t offsets[4];
	Indirect chain[4];
	Indirect *partial;
	int indirect_blks;
	int blocks_to_boundary = 0;
	int depth;
	int count = 0;
	ext4_fsblk_t first_block = 0;

	trace_ext4_ind_map_blocks_enter(inode, map->m_lblk, map->m_len, flags);
	J_ASSERT(!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)));
	J_ASSERT(handle != NULL || (flags & EXT4_GET_BLOCKS_CREATE) == 0);
	depth = ext4_block_to_path(inode, map->m_lblk, offsets,
				   &blocks_to_boundary);

	if (depth == 0)
		goto out;

	partial = ext4_get_branch(inode, depth, offsets, chain, &err);

	/* Simplest case - block found, no allocation needed */
	if (!partial) {
		first_block = le32_to_cpu(chain[depth - 1].key);
		count++;
		/*map more blocks*/
		while (count < map->m_len && count <= blocks_to_boundary) {
			ext4_fsblk_t blk;

			blk = le32_to_cpu(*(chain[depth-1].p + count));

			if (blk == first_block + count)
				count++;
			else
				break;
		}
		goto got_it;
	}

	/* Next simple case - plain lookup failed */
	if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
		unsigned epb = inode->i_sb->s_blocksize / sizeof(u32);
		int i;

		/* Count number blocks in a subtree under 'partial' */
		count = 1;
		for (i = 0; partial + i != chain + depth - 1; i++)
			count *= epb;
		/* Fill in size of a hole we found */
		map->m_pblk = 0;
		map->m_len = min_t(unsigned int, map->m_len, count);
		goto cleanup;
	}

	/* Failed read of indirect block */
	if (err == -EIO)
		goto cleanup;

	/*
         * Okay, we need to do block allocation.
        */
	if (ext4_has_feature_bigalloc(inode->i_sb)) {
		EXT4_ERROR_INODE(inode, "Can't allocate blocks for "
				 "non-extent mapped inodes with bigalloc");
		return -EFSCORRUPTED;
	}

	/* Set up for the direct block allocation */
	memset(&ar, 0, sizeof(ar));
	ar.inode = inode;
	ar.logical = map->m_lblk;
	if (S_ISREG(inode->i_mode))
		ar.flags = EXT4_MB_HINT_DATA;
	if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
		ar.flags |= EXT4_MB_DELALLOC_RESERVED;
	if (flags & EXT4_GET_BLOCKS_METADATA_NOFAIL)
		ar.flags |= EXT4_MB_USE_RESERVED;

	ar.goal = ext4_find_goal(inode, map->m_lblk, partial);

	/* the number of blocks need to allocate for [d,t]indirect blocks */
	indirect_blks = (chain + depth) - partial - 1;

	/*
         * Next look up the indirect map to count the totoal number of
         * direct blocks to allocate for this branch.
         */
	ar.len = ext4_blks_to_allocate(partial, indirect_blks,
				       map->m_len, blocks_to_boundary);

	/*
         * Block out ext4_truncate while we alter the tree
         */
	err = ext4_alloc_branch(handle, &ar, indirect_blks,
				offsets + (partial - chain), partial);

	/*
         * The ext4_splice_branch call will free and forget any buffers
         * on the new chain if there is a failure, but that risks using
         * up transaction credits, especially for bitmaps where the
         * credits cannot be returned.  Can we handle this somehow?  We
         * may need to return -EAGAIN upwards in the worst case.  --sct
         */
	if (!err)
		err = ext4_splice_branch(handle, &ar, partial, indirect_blks);
	if (err)
		goto cleanup;

	map->m_flags |= EXT4_MAP_NEW;

	ext4_update_inode_fsync_trans(handle, inode, 1);
	count = ar.len;
got_it:
	map->m_flags |= EXT4_MAP_MAPPED;
	map->m_pblk = le32_to_cpu(chain[depth-1].key);
	map->m_len = count;
	if (count > blocks_to_boundary)
		map->m_flags |= EXT4_MAP_BOUNDARY;
	err = count;
	/* Clean up and exit */
	partial = chain + depth - 1;	/* the whole chain */
cleanup:
	while (partial > chain) {
		BUFFER_TRACE(partial->bh, "call brelse");
		brelse(partial->bh);
		partial--;
	}
out:
	trace_ext4_ind_map_blocks_exit(inode, flags, map, err);
	return err;
}


Contributors
PersonTokensPropCommitsCommitProp
amir goldsteinamir goldstein44670.57%111.11%


theodore tsotheodore tso10917.25%555.56%


jan karajan kara7511.87%111.11%


darrick j. wongdarrick j. wong20.32%222.22%


Total632100.00%9100.00%



/*
 * Calculate the number of metadata blocks need to reserve
 * to allocate a new block at @lblocks for non extent file based file
 */



int ext4_ind_calc_metadata_amount(struct inode *inode, sector_t lblock)
{
	struct ext4_inode_info *ei = EXT4_I(inode);
	sector_t dind_mask = ~((sector_t)EXT4_ADDR_PER_BLOCK(inode->i_sb) - 1);
	int blk_bits;

	if (lblock < EXT4_NDIR_BLOCKS)
		return 0;

	lblock -= EXT4_NDIR_BLOCKS;

	if (ei->i_da_metadata_calc_len &&
	    (lblock & dind_mask) == ei->i_da_metadata_calc_last_lblock) {
		ei->i_da_metadata_calc_len++;
		return 0;
	}
	ei->i_da_metadata_calc_last_lblock = lblock & dind_mask;
	ei->i_da_metadata_calc_len = 1;
	blk_bits = order_base_2(lblock);
	return (blk_bits / EXT4_ADDR_PER_BLOCK_BITS(inode->i_sb)) + 1;
}


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amir goldsteinamir goldstein118100.00%1100.00%


Total118100.00%1100.00%



/*
 * Calculate number of indirect blocks touched by mapping @nrblocks logically
 * contiguous blocks
 */



int ext4_ind_trans_blocks(struct inode *inode, int nrblocks)
{
	/*
         * With N contiguous data blocks, we need at most
         * N/EXT4_ADDR_PER_BLOCK(inode->i_sb) + 1 indirect blocks,
         * 2 dindirect blocks, and 1 tindirect block
         */
	return DIV_ROUND_UP(nrblocks, EXT4_ADDR_PER_BLOCK(inode->i_sb)) + 4;
}


Contributors
PersonTokensPropCommitsCommitProp
amir goldsteinamir goldstein2896.55%150.00%


jan karajan kara13.45%150.00%


Total29100.00%2100.00%



/*
 * Truncate transactions can be complex and absolutely huge.  So we need to
 * be able to restart the transaction at a conventient checkpoint to make
 * sure we don't overflow the journal.
 *
 * Try to extend this transaction for the purposes of truncation.  If
 * extend fails, we need to propagate the failure up and restart the
 * transaction in the top-level truncate loop. --sct
 *
 * Returns 0 if we managed to create more room.  If we can't create more
 * room, and the transaction must be restarted we return 1.
 */



static int try_to_extend_transaction(handle_t *handle, struct inode *inode)
{
	if (!ext4_handle_valid(handle))
		return 0;
	if (ext4_handle_has_enough_credits(handle, EXT4_RESERVE_TRANS_BLOCKS+1))
		return 0;
	if (!ext4_journal_extend(handle, ext4_blocks_for_truncate(inode)))
		return 0;
	return 1;
}


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amir goldsteinamir goldstein59100.00%1100.00%


Total59100.00%1100.00%



/*
 * Probably it should be a library function... search for first non-zero word
 * or memcmp with zero_page, whatever is better for particular architecture.
 * Linus?
 */



static inline int all_zeroes(__le32 *p, __le32 *q)
{
	while (p < q)
		if (*p++)
			return 0;
	return 1;
}


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amir goldsteinamir goldstein33100.00%1100.00%


Total33100.00%1100.00%



/**
 *      ext4_find_shared - find the indirect blocks for partial truncation.
 *      @inode:   inode in question
 *      @depth:   depth of the affected branch
 *      @offsets: offsets of pointers in that branch (see ext4_block_to_path)
 *      @chain:   place to store the pointers to partial indirect blocks
 *      @top:     place to the (detached) top of branch
 *
 *      This is a helper function used by ext4_truncate().
 *
 *      When we do truncate() we may have to clean the ends of several
 *      indirect blocks but leave the blocks themselves alive. Block is
 *      partially truncated if some data below the new i_size is referred
 *      from it (and it is on the path to the first completely truncated
 *      data block, indeed).  We have to free the top of that path along
 *      with everything to the right of the path. Since no allocation
 *      past the truncation point is possible until ext4_truncate()
 *      finishes, we may safely do the latter, but top of branch may
 *      require special attention - pageout below the truncation point
 *      might try to populate it.
 *
 *      We atomically detach the top of branch from the tree, store the
 *      block number of its root in *@top, pointers to buffer_heads of
 *      partially truncated blocks - in @chain[].bh and pointers to
 *      their last elements that should not be removed - in
 *      @chain[].p. Return value is the pointer to last filled element
 *      of @chain.
 *
 *      The work left to caller to do the actual freeing of subtrees:
 *              a) free the subtree starting from *@top
 *              b) free the subtrees whose roots are stored in
 *                      (@chain[i].p+1 .. end of @chain[i].bh->b_data)
 *              c) free the subtrees growing from the inode past the @chain[0].
 *                      (no partially truncated stuff there).  */




static Indirect *ext4_find_shared(struct inode *inode, int depth,
				  ext4_lblk_t offsets[4], Indirect chain[4],
				  __le32 *top)
{
	Indirect *partial, *p;
	int k, err;

	*top = 0;
	/* Make k index the deepest non-null offset + 1 */
	for (k = depth; k > 1 && !offsets[k-1]; k--)
		;
	partial = ext4_get_branch(inode, k, offsets, chain, &err);
	/* Writer: pointers */
	if (!partial)
		partial = chain + k-1;
	/*
         * If the branch acquired continuation since we've looked at it -
         * fine, it should all survive and (new) top doesn't belong to us.
         */
	if (!partial->key && *partial->p)
		/* Writer: end */
		goto no_top;
	for (p = partial; (p > chain) && all_zeroes((__le32 *) p->bh->b_data, p->p); p--)
		;
	/*
         * OK, we've found the last block that must survive. The rest of our
         * branch should be detached before unlocking. However, if that rest
         * of branch is all ours and does not grow immediately from the inode
         * it's easier to cheat and just decrement partial->p.
         */
	if (p == chain + k - 1 && p > chain) {
		p->p--;
	} else {
		*top = *p->p;
		/* Nope, don't do this in ext4.  Must leave the tree intact */
#if 0
		*p->p = 0;
#endif
	}
	/* Writer: end */

	while (partial > p) {
		brelse(partial->bh);
		partial--;
	}
no_top:
	return partial;
}


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amir goldsteinamir goldstein215100.00%1100.00%


Total215100.00%1100.00%



/*
 * Zero a number of block pointers in either an inode or an indirect block.
 * If we restart the transaction we must again get write access to the
 * indirect block for further modification.
 *
 * We release `count' blocks on disk, but (last - first) may be greater
 * than `count' because there can be holes in there.
 *
 * Return 0 on success, 1 on invalid block range
 * and < 0 on fatal error.
 */



static int ext4_clear_blocks(handle_t *handle, struct inode *inode,
			     struct buffer_head *bh,
			     ext4_fsblk_t block_to_free,
			     unsigned long count, __le32 *first,
			     __le32 *last)
{
	__le32 *p;
	int	flags = EXT4_FREE_BLOCKS_VALIDATED;
	int	err;

	if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
		flags |= EXT4_FREE_BLOCKS_FORGET | EXT4_FREE_BLOCKS_METADATA;
	else if (ext4_should_journal_data(inode))
		flags |= EXT4_FREE_BLOCKS_FORGET;

	if (!ext4_data_block_valid(EXT4_SB(inode->i_sb), block_to_free,
				   count)) {
		EXT4_ERROR_INODE(inode, "attempt to clear invalid "
				 "blocks %llu len %lu",
				 (unsigned long long) block_to_free, count);
		return 1;
	}

	if (try_to_extend_transaction(handle, inode)) {
		if (bh) {
			BUFFER_TRACE(bh, "call ext4_handle_dirty_metadata");
			err = ext4_handle_dirty_metadata(handle, inode,