xfs_da_btree.c

linux 内核源代码

	node1 = blk1->bp->data;
	node2 = blk2->bp->data;
	/*
	 * Figure out how many entries need to move, and in which direction.
	 * Swap the nodes around if that makes it simpler.
	 */
	if ((be16_to_cpu(node1->hdr.count) > 0) && (be16_to_cpu(node2->hdr.count) > 0) &&
	    ((be32_to_cpu(node2->btree[0].hashval) < be32_to_cpu(node1->btree[0].hashval)) ||
	     (be32_to_cpu(node2->btree[be16_to_cpu(node2->hdr.count)-1].hashval) <
	      be32_to_cpu(node1->btree[be16_to_cpu(node1->hdr.count)-1].hashval)))) {
		tmpnode = node1;
		node1 = node2;
		node2 = tmpnode;
	}
	ASSERT(be16_to_cpu(node1->hdr.info.magic) == XFS_DA_NODE_MAGIC);
	ASSERT(be16_to_cpu(node2->hdr.info.magic) == XFS_DA_NODE_MAGIC);
	count = (be16_to_cpu(node1->hdr.count) - be16_to_cpu(node2->hdr.count)) / 2;
	if (count == 0)
		return;
	tp = state->args->trans;
	/*
	 * Two cases: high-to-low and low-to-high.
	 */
	if (count > 0) {
		/*
		 * Move elements in node2 up to make a hole.
		 */
		if ((tmp = be16_to_cpu(node2->hdr.count)) > 0) {
			tmp *= (uint)sizeof(xfs_da_node_entry_t);
			btree_s = &node2->btree[0];
			btree_d = &node2->btree[count];
			memmove(btree_d, btree_s, tmp);
		}

		/*
		 * Move the req'd B-tree elements from high in node1 to
		 * low in node2.
		 */
		be16_add(&node2->hdr.count, count);
		tmp = count * (uint)sizeof(xfs_da_node_entry_t);
		btree_s = &node1->btree[be16_to_cpu(node1->hdr.count) - count];
		btree_d = &node2->btree[0];
		memcpy(btree_d, btree_s, tmp);
		be16_add(&node1->hdr.count, -count);
	} else {
		/*
		 * Move the req'd B-tree elements from low in node2 to
		 * high in node1.
		 */
		count = -count;
		tmp = count * (uint)sizeof(xfs_da_node_entry_t);
		btree_s = &node2->btree[0];
		btree_d = &node1->btree[be16_to_cpu(node1->hdr.count)];
		memcpy(btree_d, btree_s, tmp);
		be16_add(&node1->hdr.count, count);
		xfs_da_log_buf(tp, blk1->bp,
			XFS_DA_LOGRANGE(node1, btree_d, tmp));

		/*
		 * Move elements in node2 down to fill the hole.
		 */
		tmp  = be16_to_cpu(node2->hdr.count) - count;
		tmp *= (uint)sizeof(xfs_da_node_entry_t);
		btree_s = &node2->btree[count];
		btree_d = &node2->btree[0];
		memmove(btree_d, btree_s, tmp);
		be16_add(&node2->hdr.count, -count);
	}

	/*
	 * Log header of node 1 and all current bits of node 2.
	 */
	xfs_da_log_buf(tp, blk1->bp,
		XFS_DA_LOGRANGE(node1, &node1->hdr, sizeof(node1->hdr)));
	xfs_da_log_buf(tp, blk2->bp,
		XFS_DA_LOGRANGE(node2, &node2->hdr,
			sizeof(node2->hdr) +
			sizeof(node2->btree[0]) * be16_to_cpu(node2->hdr.count)));

	/*
	 * Record the last hashval from each block for upward propagation.
	 * (note: don't use the swapped node pointers)
	 */
	node1 = blk1->bp->data;
	node2 = blk2->bp->data;
	blk1->hashval = be32_to_cpu(node1->btree[be16_to_cpu(node1->hdr.count)-1].hashval);
	blk2->hashval = be32_to_cpu(node2->btree[be16_to_cpu(node2->hdr.count)-1].hashval);

	/*
	 * Adjust the expected index for insertion.
	 */
	if (blk1->index >= be16_to_cpu(node1->hdr.count)) {
		blk2->index = blk1->index - be16_to_cpu(node1->hdr.count);
		blk1->index = be16_to_cpu(node1->hdr.count) + 1;	/* make it invalid */
	}
}

/*
 * Add a new entry to an intermediate node.
 */
STATIC void
xfs_da_node_add(xfs_da_state_t *state, xfs_da_state_blk_t *oldblk,
			       xfs_da_state_blk_t *newblk)
{
	xfs_da_intnode_t *node;
	xfs_da_node_entry_t *btree;
	int tmp;
	xfs_mount_t *mp;

	node = oldblk->bp->data;
	mp = state->mp;
	ASSERT(be16_to_cpu(node->hdr.info.magic) == XFS_DA_NODE_MAGIC);
	ASSERT((oldblk->index >= 0) && (oldblk->index <= be16_to_cpu(node->hdr.count)));
	ASSERT(newblk->blkno != 0);
	if (state->args->whichfork == XFS_DATA_FORK)
		ASSERT(newblk->blkno >= mp->m_dirleafblk &&
		       newblk->blkno < mp->m_dirfreeblk);

	/*
	 * We may need to make some room before we insert the new node.
	 */
	tmp = 0;
	btree = &node->btree[ oldblk->index ];
	if (oldblk->index < be16_to_cpu(node->hdr.count)) {
		tmp = (be16_to_cpu(node->hdr.count) - oldblk->index) * (uint)sizeof(*btree);
		memmove(btree + 1, btree, tmp);
	}
	btree->hashval = cpu_to_be32(newblk->hashval);
	btree->before = cpu_to_be32(newblk->blkno);
	xfs_da_log_buf(state->args->trans, oldblk->bp,
		XFS_DA_LOGRANGE(node, btree, tmp + sizeof(*btree)));
	be16_add(&node->hdr.count, 1);
	xfs_da_log_buf(state->args->trans, oldblk->bp,
		XFS_DA_LOGRANGE(node, &node->hdr, sizeof(node->hdr)));

	/*
	 * Copy the last hash value from the oldblk to propagate upwards.
	 */
	oldblk->hashval = be32_to_cpu(node->btree[be16_to_cpu(node->hdr.count)-1 ].hashval);
}

/*========================================================================
 * Routines used for shrinking the Btree.
 *========================================================================*/

/*
 * Deallocate an empty leaf node, remove it from its parent,
 * possibly deallocating that block, etc...
 */
int
xfs_da_join(xfs_da_state_t *state)
{
	xfs_da_state_blk_t *drop_blk, *save_blk;
	int action, error;

	action = 0;
	drop_blk = &state->path.blk[ state->path.active-1 ];
	save_blk = &state->altpath.blk[ state->path.active-1 ];
	ASSERT(state->path.blk[0].magic == XFS_DA_NODE_MAGIC);
	ASSERT(drop_blk->magic == XFS_ATTR_LEAF_MAGIC ||
	       drop_blk->magic == XFS_DIR2_LEAFN_MAGIC);

	/*
	 * Walk back up the tree joining/deallocating as necessary.
	 * When we stop dropping blocks, break out.
	 */
	for (  ; state->path.active >= 2; drop_blk--, save_blk--,
		 state->path.active--) {
		/*
		 * See if we can combine the block with a neighbor.
		 *   (action == 0) => no options, just leave
		 *   (action == 1) => coalesce, then unlink
		 *   (action == 2) => block empty, unlink it
		 */
		switch (drop_blk->magic) {
		case XFS_ATTR_LEAF_MAGIC:
			error = xfs_attr_leaf_toosmall(state, &action);
			if (error)
				return(error);
			if (action == 0)
				return(0);
			xfs_attr_leaf_unbalance(state, drop_blk, save_blk);
			break;
		case XFS_DIR2_LEAFN_MAGIC:
			error = xfs_dir2_leafn_toosmall(state, &action);
			if (error)
				return error;
			if (action == 0)
				return 0;
			xfs_dir2_leafn_unbalance(state, drop_blk, save_blk);
			break;
		case XFS_DA_NODE_MAGIC:
			/*
			 * Remove the offending node, fixup hashvals,
			 * check for a toosmall neighbor.
			 */
			xfs_da_node_remove(state, drop_blk);
			xfs_da_fixhashpath(state, &state->path);
			error = xfs_da_node_toosmall(state, &action);
			if (error)
				return(error);
			if (action == 0)
				return 0;
			xfs_da_node_unbalance(state, drop_blk, save_blk);
			break;
		}
		xfs_da_fixhashpath(state, &state->altpath);
		error = xfs_da_blk_unlink(state, drop_blk, save_blk);
		xfs_da_state_kill_altpath(state);
		if (error)
			return(error);
		error = xfs_da_shrink_inode(state->args, drop_blk->blkno,
							 drop_blk->bp);
		drop_blk->bp = NULL;
		if (error)
			return(error);
	}
	/*
	 * We joined all the way to the top.  If it turns out that
	 * we only have one entry in the root, make the child block
	 * the new root.
	 */
	xfs_da_node_remove(state, drop_blk);
	xfs_da_fixhashpath(state, &state->path);
	error = xfs_da_root_join(state, &state->path.blk[0]);
	return(error);
}

/*
 * We have only one entry in the root.  Copy the only remaining child of
 * the old root to block 0 as the new root node.
 */
STATIC int
xfs_da_root_join(xfs_da_state_t *state, xfs_da_state_blk_t *root_blk)
{
	xfs_da_intnode_t *oldroot;
	/* REFERENCED */
	xfs_da_blkinfo_t *blkinfo;
	xfs_da_args_t *args;
	xfs_dablk_t child;
	xfs_dabuf_t *bp;
	int error;

	args = state->args;
	ASSERT(args != NULL);
	ASSERT(root_blk->magic == XFS_DA_NODE_MAGIC);
	oldroot = root_blk->bp->data;
	ASSERT(be16_to_cpu(oldroot->hdr.info.magic) == XFS_DA_NODE_MAGIC);
	ASSERT(!oldroot->hdr.info.forw);
	ASSERT(!oldroot->hdr.info.back);

	/*
	 * If the root has more than one child, then don't do anything.
	 */
	if (be16_to_cpu(oldroot->hdr.count) > 1)
		return(0);

	/*
	 * Read in the (only) child block, then copy those bytes into
	 * the root block's buffer and free the original child block.
	 */
	child = be32_to_cpu(oldroot->btree[0].before);
	ASSERT(child != 0);
	error = xfs_da_read_buf(args->trans, args->dp, child, -1, &bp,
					     args->whichfork);
	if (error)
		return(error);
	ASSERT(bp != NULL);
	blkinfo = bp->data;
	if (be16_to_cpu(oldroot->hdr.level) == 1) {
		ASSERT(be16_to_cpu(blkinfo->magic) == XFS_DIR2_LEAFN_MAGIC ||
		       be16_to_cpu(blkinfo->magic) == XFS_ATTR_LEAF_MAGIC);
	} else {
		ASSERT(be16_to_cpu(blkinfo->magic) == XFS_DA_NODE_MAGIC);
	}
	ASSERT(!blkinfo->forw);
	ASSERT(!blkinfo->back);
	memcpy(root_blk->bp->data, bp->data, state->blocksize);
	xfs_da_log_buf(args->trans, root_blk->bp, 0, state->blocksize - 1);
	error = xfs_da_shrink_inode(args, child, bp);
	return(error);
}

/*
 * Check a node block and its neighbors to see if the block should be
 * collapsed into one or the other neighbor.  Always keep the block
 * with the smaller block number.
 * If the current block is over 50% full, don't try to join it, return 0.
 * If the block is empty, fill in the state structure and return 2.
 * If it can be collapsed, fill in the state structure and return 1.
 * If nothing can be done, return 0.
 */
STATIC int
xfs_da_node_toosmall(xfs_da_state_t *state, int *action)
{
	xfs_da_intnode_t *node;
	xfs_da_state_blk_t *blk;
	xfs_da_blkinfo_t *info;
	int count, forward, error, retval, i;
	xfs_dablk_t blkno;
	xfs_dabuf_t *bp;

	/*
	 * Check for the degenerate case of the block being over 50% full.
	 * If so, it's not worth even looking to see if we might be able
	 * to coalesce with a sibling.
	 */
	blk = &state->path.blk[ state->path.active-1 ];
	info = blk->bp->data;
	ASSERT(be16_to_cpu(info->magic) == XFS_DA_NODE_MAGIC);
	node = (xfs_da_intnode_t *)info;
	count = be16_to_cpu(node->hdr.count);
	if (count > (state->node_ents >> 1)) {
		*action = 0;	/* blk over 50%, don't try to join */
		return(0);	/* blk over 50%, don't try to join */
	}

	/*
	 * Check for the degenerate case of the block being empty.
	 * If the block is empty, we'll simply delete it, no need to
	 * coalesce it with a sibling block.  We choose (arbitrarily)
	 * to merge with the forward block unless it is NULL.
	 */
	if (count == 0) {
		/*
		 * Make altpath point to the block we want to keep and
		 * path point to the block we want to drop (this one).
		 */
		forward = (info->forw != 0);
		memcpy(&state->altpath, &state->path, sizeof(state->path));
		error = xfs_da_path_shift(state, &state->altpath, forward,
						 0, &retval);
		if (error)
			return(error);
		if (retval) {
			*action = 0;
		} else {
			*action = 2;
		}
		return(0);
	}

	/*
	 * Examine each sibling block to see if we can coalesce with
	 * at least 25% free space to spare.  We need to figure out
	 * whether to merge with the forward or the backward block.
	 * We prefer coalescing with the lower numbered sibling so as
	 * to shrink a directory over time.
	 */
	/* start with smaller blk num */
	forward = (be32_to_cpu(info->forw) < be32_to_cpu(info->back));
	for (i = 0; i < 2; forward = !forward, i++) {
		if (forward)
			blkno = be32_to_cpu(info->forw);
		else
			blkno = be32_to_cpu(info->back);
		if (blkno == 0)
			continue;
		error = xfs_da_read_buf(state->args->trans, state->args->dp,
					blkno, -1, &bp, state->args->whichfork);
		if (error)
			return(error);
		ASSERT(bp != NULL);

		node = (xfs_da_intnode_t *)info;
		count  = state->node_ents;
		count -= state->node_ents >> 2;
		count -= be16_to_cpu(node->hdr.count);
		node = bp->data;
		ASSERT(be16_to_cpu(node->hdr.info.magic) == XFS_DA_NODE_MAGIC);
		count -= be16_to_cpu(node->hdr.count);
		xfs_da_brelse(state->args->trans, bp);
		if (count >= 0)
			break;	/* fits with at least 25% to spare */
	}
	if (i >= 2) {
		*action = 0;
		return(0);
	}

	/*
	 * Make altpath point to the block we want to keep (the lower
	 * numbered block) and path point to the block we want to drop.
	 */
	memcpy(&state->altpath, &state->path, sizeof(state->path));
	if (blkno < blk->blkno) {
		error = xfs_da_path_shift(state, &state->altpath, forward,
						 0, &retval);
		if (error) {
			return(error);
		}
		if (retval) {
			*action = 0;
			return(0);
		}
	} else {
		error = xfs_da_path_shift(state, &state->path, forward,
						 0, &retval);
		if (error) {
			return(error);
		}
		if (retval) {
			*action = 0;
			return(0);
		}
	}
	*action = 1;
	return(0);
}

/*
 * Walk back up the tree adjusting hash values as necessary,
 * when we stop making changes, return.
 */
void
xfs_da_fixhashpath(xfs_da_state_t *state, xfs_da_state_path_t *path)
{
	xfs_da_state_blk_t *blk;
	xfs_da_intnode_t *node;
	xfs_da_node_entry_t *btree;
	xfs_dahash_t lasthash=0;
	int level, count;

	level = path->active-1;
	blk = &path->blk[ level ];
	switch (blk->magic) {
	case XFS_ATTR_LEAF_MAGIC:
		lasthash = xfs_attr_leaf_lasthash(blk->bp, &count);
		if (count == 0)
			return;
		break;
	case XFS_DIR2_LEAFN_MAGIC:
		lasthash = xfs_dir2_leafn_lasthash(blk->bp, &count);
		if (count == 0)
			return;
		break;
	case XFS_DA_NODE_MAGIC:
		lasthash = xfs_da_node_lasthash(blk->bp, &count);
		if (count == 0)
			return;
		break;
	}
	for (blk--, level--; level >= 0; blk--, level--) {
		node = blk->bp->data;
		ASSERT(be16_to_cpu(node->hdr.info.magic) == XFS_DA_NODE_MAGIC);
		btree = &node->btree[ blk->index ];
		if (be32_to_cpu(btree->hashval) == lasthash)
			break;
		blk->hashval = lasthash;
		btree->hashval = cpu_to_be32(lasthash);
		xfs_da_log_buf(state->args->trans, blk->bp,
				  XFS_DA_LOGRANGE(node, btree, sizeof(*btree)));

		lasthash = be32_to_cpu(node->btree[be16_to_cpu(node->hdr.count)-1].hashval);
	}
}

/*
 * Remove an entry from an intermediate node.
 */
STATIC void
xfs_da_node_remove(xfs_da_state_t *state, xfs_da_state_blk_t *drop_blk)
{
	xfs_da_intnode_t *node;
	xfs_da_node_entry_t *btree;
	int tmp;

	node = drop_blk->bp->data;
	ASSERT(drop_blk->index < be16_to_cpu(node->hdr.count));
	ASSERT(drop_blk->index >= 0);

	/*
	 * Copy over the offending entry, or just zero it out.