Re: [PATCH] ext4: try fast merge operation in ext4_mb_free_metadata()

["Aneesh Kumar K. V" <aneesh.kumar@linux.vnet.ibm.com>]

On Wed, 24 Mar 2010 21:32:39 +0800, jing zhang <zj.barak@gmail.com> wrote:
> From: Jing Zhang <zj.barak@gmail.com>
> 
> Date: Wed Mar 24 21:30:22     2010
> 
> There may exist fast path for merge if merge-able.
> 
> Cc: Theodore Ts'o <tytso@mit.edu>
> Cc: Andreas Dilger <adilger@sun.com>
> Cc: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
> Signed-off-by: Jing Zhang <zj.barak@gmail.com>
> 
> ---
> 
> --- linux-2.6.32/fs/ext4/mballoc.c	2009-12-03 11:51:22.000000000 +0800
> +++ ext4_mm_leak/mballoc7.c	2010-03-24 21:27:24.000000000 +0800
> @@ -4385,6 +4385,24 @@ ext4_mb_free_metadata(handle_t *handle,
>  		}
>  	}
> 
> +	if (parent) {
> +		/* let's try fast path */
> +		entry = rb_entry(parent, struct ext4_free_data, node);
> +		if (n == &parent->rb_left) {
> +			if (can_merge(new_entry, entry)) {
> +				entry->start_blk = new_entry->start_blk;
> +				entry->count += new_entry->count;
> +				/* and info the caller that new_entry is
> +				 * not used yet.
> +				 */
> +				return 0;

return 0 on success so you may want -1 here 

> +			}
> +		}
> +		else if (can_merge(entry, new_entry)) {
> +			entry->count += new_entry->count;
> +			return 0;
> +		}
> +	}
>  	rb_link_node(new_node, parent, n);
>  	rb_insert_color(new_node, &db->bb_free_root);
> --

-aneesh