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

[jing zhang <zj.barak@gmail.com>]

2010/3/25, 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

Agree.

      - zj

>
>> +			}
>> +		}
>> +		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
>