[Ocfs2-devel] [PATCH 02/15] ocfs2: Add clusters free in dealloc_ctxt.

[Joel Becker <Joel.Becker@oracle.com>]

On Thu, Oct 30, 2008 at 01:42:12PM +0800, Tao Ma wrote:
> Now in ocfs2 xattr set, the whole process are divided into many small
> parts and they are wrapped into diffrent transactions and it make the
> set doesn't look like a real transaction. So we want to integrate it
> into a real one.
> 
> In some cases we will allocate some clusters and free some in just one
> transaction. e.g, one xattr is larger than inline size, so it and its
> value root is stored within the inode while the value is outside in a
> cluster. Then we try to update it with a smaller value(larger than the
> size of root but smaller than inline size), we may need to free the
> outside cluster while allocate a new bucket(one cluster) since now the
> inode may be full. The old solution will lock the global_bitmap(if the
> local alloc failed in stress test) and then the truncate log. This will
> cause a ABBA lock with truncate log flush.
> 
> This patch add the clusters free in dealloc_ctxt, so that we can record
> the free clusters during the transaction and then free it after we
> release the global_bitmap in xattr set.

	So, you're really adding the global cluster allocator as a type
of allocator that can live on the dealloc context.

> diff --git a/fs/ocfs2/alloc.c b/fs/ocfs2/alloc.c
> index 0cc2deb..3c54572 100644
> --- a/fs/ocfs2/alloc.c
> +++ b/fs/ocfs2/alloc.c
> @@ -5801,6 +5801,11 @@ int ocfs2_truncate_log_init(struct ocfs2_super *osb)
>  
>  /*
>   * Describes a single block free from a suballocator
> + *
> + * XXX:
> + * This structure is reused when we free a number of clusters
> + * during xattr set. In that case, free_bit indicates the number
> + * of the free clusters.
>   */

How about:

  /*
   * Describe a single bit freed from a suballocator.  For the block
   * suballocators, it represents one block.  For the global cluster
   * allocator, it represents one cluster.
   */

>  struct ocfs2_cached_block_free {
>  	struct ocfs2_cached_block_free		*free_next;
> @@ -5893,6 +5898,73 @@ out:
>  	return ret;
>  }
>  
> +int ocfs2_cache_clusters_dealloc(struct ocfs2_cached_dealloc_ctxt *ctxt,
> +				 u64 blkno, unsigned int bit)

	Call it ocfs2_cache_cluster_dealloc() for consistency (the
singular form).

> +{
> +	int ret = 0;
> +	struct ocfs2_cached_block_free *item;
> +
> +	item = kmalloc(sizeof(*item), GFP_NOFS);
> +	if (item == NULL) {
> +		ret = -ENOMEM;
> +		mlog_errno(ret);
> +		return ret;
> +	}
> +
> +	mlog(0, "Insert clusters: (bit %u, blk %llu)\n",
> +	     bit, (unsigned long long)blkno);
> +
> +	item->free_blk = blkno;
> +	item->free_bit = bit;
> +	item->free_next = ctxt->c_clusters_list;

	You need to push item on to the list too.

  +	ctxt->c_clusters_list = item;

> +
> +	return ret;
> +}
> +
> +static int ocfs2_free_clusters_list(struct ocfs2_super *osb,
> +				    struct ocfs2_cached_block_free *head)

	Call this 'ocfs2_free_cached_clusters' and change
'ocfs2_free_cached_items' to 'ocfs2_free_cached_blocks'.

> +{
> +	struct ocfs2_cached_block_free *tmp;
> +	struct inode *tl_inode = osb->osb_tl_inode;
> +	handle_t *handle;
> +	int ret = 0;
> +
> +	mutex_lock(&tl_inode->i_mutex);
> +
> +	handle = ocfs2_start_trans(osb, OCFS2_TRUNCATE_LOG_UPDATE);
> +	if (IS_ERR(handle)) {
> +		ret = PTR_ERR(handle);
> +		mlog_errno(ret);
> +		goto out_mutex;
> +	}
> +
> +	while (head) {
> +		ret = ocfs2_truncate_log_append(osb, handle, head->free_blk,
> +						head->free_bit);
> +		if (ret) {
> +			mlog_errno(ret);
> +			break;
> +		}

	What happens if the truncate log fills up?

> +		tmp = head;
> +		head = head->free_next;
> +		kfree(tmp);
> +	}
> +
> +	ocfs2_commit_trans(osb, handle);
> +
> +out_mutex:
> +	mutex_unlock(&tl_inode->i_mutex);
> +
> +	while (head) {
> +		/* Premature exit may have left some dangling items. */
> +		tmp = head;
> +		head = head->free_next;
> +		kfree(tmp);
> +	}
> +
> +	return ret;
> +}
> +
>  int ocfs2_run_deallocs(struct ocfs2_super *osb,
>  		       struct ocfs2_cached_dealloc_ctxt *ctxt)
>  {

<snip>

> diff --git a/fs/ocfs2/alloc.h b/fs/ocfs2/alloc.h
> index 70257c8..1333a92 100644
> --- a/fs/ocfs2/alloc.h
> +++ b/fs/ocfs2/alloc.h
> @@ -167,11 +167,15 @@ int __ocfs2_flush_truncate_log(struct ocfs2_super *osb);
>   */
>  struct ocfs2_cached_dealloc_ctxt {
>  	struct ocfs2_per_slot_free_list		*c_first_suballocator;
> +	struct ocfs2_cached_block_free 		*c_clusters_list;

	Change 'c_clusters_list' to 'c_global_allocator'.

Joel

-- 

"If you took all of the grains of sand in the world, and lined
 them up end to end in a row, you'd be working for the government!"
	- Mr. Interesting

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker at oracle.com
Phone: (650) 506-8127