[Ocfs2-devel] [PATCH 12/15] Add xattr find process for xattr index btree.v2

[Mark Fasheh]

On Fri, Jun 27, 2008 at 03:02:35PM +0800, Tao Ma wrote:
> +static int ocfs2_cp_xattr_bucket_to_buffer(struct inode *inode,
> +					   u64 blkno,
> +					   char *buffer)
> +{
> +	int i, ret, block_num = ocfs2_blocks_per_xattr_bucket(inode->i_sb);
> +	int blocksize = inode->i_sb->s_blocksize;
> +	struct buffer_head **bhs = NULL;
> +	char *target;
> +
> +	bhs = kzalloc(sizeof(struct buffer_head *) * block_num, GFP_NOFS);
> +	ret = ocfs2_read_xattr_bucket(inode, blkno, bhs, 0);
> +	if (ret)
> +		goto out;
> +
> +	target = buffer;
> +	for (i = 0; i < block_num; i++, target += blocksize)
> +		memcpy(target, bhs[i]->b_data, blocksize);
> +
> +out:
> +	if (bhs) {
> +		for (i = 0; i < block_num; i++)
> +			brelse(bhs[i]);
> +		kfree(bhs);
> +	}
> +	return ret;
> +}
> +
> +/*
> + * Find the specided xattr entry in a series of buckets.
> + * This series start from p_blkno and last for num_clusters.
> + * The ocfs2_xattr_header.xh_reserved1 of the first bucket contains
> + * the num of the valid buckets.
> + *
> + * Return the buffer_head this xattr should reside in. And if the xattr's
> + * hash is in the gap of 2 buckets, return the lower bucket.
> + */
> +static int ocfs2_xattr_bucket_find(struct inode *inode,
> +				   int name_index,
> +				   const char *name,
> +				   u32 name_hash,
> +				   u64 p_blkno,
> +				   u32 first_hash,
> +				   u32 num_clusters,
> +				   struct ocfs2_xattr_search *xs)
> +{
> +	int ret, found = 0;
> +	struct buffer_head *bh = NULL;
> +	struct buffer_head *last_bh = NULL;
> +	struct buffer_head *lower_bh = NULL;
> +	struct ocfs2_xattr_header *xh = NULL;
> +	struct ocfs2_xattr_entry *xe = NULL;
> +	u16 xh_count, xe_index = 0;
> +	u16 block_in_bucket = ocfs2_blocks_per_xattr_bucket(inode->i_sb);
> +	int low_bucket = 0, bucket, high_bucket;
> +	int blocksize = inode->i_sb->s_blocksize;
> +	u32 last_hash;
> +	u64 blkno;
> +
> +	ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), p_blkno,
> +			       &bh, OCFS2_BH_CACHED, inode);
> +	if (ret)
> +		goto out;
> +	xh = (struct ocfs2_xattr_header *)bh->b_data;
> +	high_bucket = le16_to_cpu(xh->xh_reserved1) - 1;
> +
> +	while (low_bucket <= high_bucket) {
> +		brelse(bh);
> +		bh = last_bh = NULL;
> +		bucket = (low_bucket + high_bucket) / 2;
> +
> +		blkno = p_blkno + bucket * block_in_bucket;
> +
> +		ret = ocfs2_read_block(OCFS2_SB(inode->i_sb), blkno,
> +				       &bh, OCFS2_BH_CACHED, inode);
> +		if (ret) {
> +			mlog_errno(ret);
> +			goto out;
> +		}
> +
> +		xh = (struct ocfs2_xattr_header *)bh->b_data;
> +		xe = &xh->xh_entries[0];
> +		if (name_hash < le32_to_cpu(xe->xe_name_hash)) {
> +			high_bucket = bucket - 1;
> +			continue;
> +		}

This function looks like it's doing a lot of random I/O. What about sucking
up some large numbers of (contiguous) blocks with a readahead request before
going into this function? The beauty of how our readhead works is that you
wouldn't have to change a single line of code here...

--
Mark Fasheh