[PATCH] Btrfs: optimize to remove unnecessary removal with ulist reallocation

[PATCH] Btrfs: optimize to remove unnecessary removal with ulist reallocation

[Wang Shilong]

Here we are not going to free memory, no need to remove every node
one by one, just init root node here is ok.

Cc:  Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
---
 fs/btrfs/ulist.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/btrfs/ulist.c b/fs/btrfs/ulist.c
index b0a523b2..35f5de9 100644
--- a/fs/btrfs/ulist.c
+++ b/fs/btrfs/ulist.c
@@ -207,9 +207,6 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
 		void *old = NULL;
 		int i;
 
-		for (i = 0; i < ulist->nnodes; i++)
-			rb_erase(&ulist->nodes[i].rb_node, &ulist->root);
-
 		/*
 		 * if nodes_alloced == ULIST_SIZE no memory has been allocated
 		 * yet, so pass NULL to krealloc
@@ -234,6 +231,7 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
 		 * pointers, so we have to do it ourselves.  Otherwise we may
 		 * be bitten by crashes.
 		 */
+		ulist->root = RB_ROOT;
 		for (i = 0; i < ulist->nnodes; i++) {
 			ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
 			if (ret < 0)
-- 
1.8.3.1

Re: [PATCH] Btrfs: optimize to remove unnecessary removal with ulist reallocation

[Liu Bo]

On Fri, Jan 10, 2014 at 09:25:46PM +0800, Wang Shilong wrote:
> Here we are not going to free memory, no need to remove every node
> one by one, just init root node here is ok.

Looks fine, but we need to make sure that it passes the regression test since you're
working on an old bug.

-liubo

> 
> Cc:  Liu Bo <bo.li.liu@oracle.com>
> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
> ---
>  fs/btrfs/ulist.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/fs/btrfs/ulist.c b/fs/btrfs/ulist.c
> index b0a523b2..35f5de9 100644
> --- a/fs/btrfs/ulist.c
> +++ b/fs/btrfs/ulist.c
> @@ -207,9 +207,6 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
>  		void *old = NULL;
>  		int i;
>  
> -		for (i = 0; i < ulist->nnodes; i++)
> -			rb_erase(&ulist->nodes[i].rb_node, &ulist->root);
> -
>  		/*
>  		 * if nodes_alloced == ULIST_SIZE no memory has been allocated
>  		 * yet, so pass NULL to krealloc
> @@ -234,6 +231,7 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
>  		 * pointers, so we have to do it ourselves.  Otherwise we may
>  		 * be bitten by crashes.
>  		 */
> +		ulist->root = RB_ROOT;
>  		for (i = 0; i < ulist->nnodes; i++) {
>  			ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
>  			if (ret < 0)
> -- 
> 1.8.3.1
> 

Re: [PATCH] Btrfs: optimize to remove unnecessary removal with ulist reallocation

[Wang Shilong]

Hi Liu,

On 01/13/2014 10:31 AM, Liu Bo wrote:
> On Fri, Jan 10, 2014 at 09:25:46PM +0800, Wang Shilong wrote:
>> Here we are not going to free memory, no need to remove every node
>> one by one, just init root node here is ok.
> Looks fine, but we need to make sure that it passes the regression test since you're
> working on an old bug.
Sorry for late reply, i have just sent a regression test for this.

I did some hacking in kernel codes, and make sure test covers
ulist reallocation, hopely it is helpful in the future.^_^

url can be seen:
https://patchwork.kernel.org/patch/3533801/


Thanks,
Wang
>
> -liubo
>
>> Cc:  Liu Bo <bo.li.liu@oracle.com>
>> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com>
>> ---
>>   fs/btrfs/ulist.c | 4 +---
>>   1 file changed, 1 insertion(+), 3 deletions(-)
>>
>> diff --git a/fs/btrfs/ulist.c b/fs/btrfs/ulist.c
>> index b0a523b2..35f5de9 100644
>> --- a/fs/btrfs/ulist.c
>> +++ b/fs/btrfs/ulist.c
>> @@ -207,9 +207,6 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
>>   		void *old = NULL;
>>   		int i;
>>   
>> -		for (i = 0; i < ulist->nnodes; i++)
>> -			rb_erase(&ulist->nodes[i].rb_node, &ulist->root);
>> -
>>   		/*
>>   		 * if nodes_alloced == ULIST_SIZE no memory has been allocated
>>   		 * yet, so pass NULL to krealloc
>> @@ -234,6 +231,7 @@ int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
>>   		 * pointers, so we have to do it ourselves.  Otherwise we may
>>   		 * be bitten by crashes.
>>   		 */
>> +		ulist->root = RB_ROOT;
>>   		for (i = 0; i < ulist->nnodes; i++) {
>>   			ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
>>   			if (ret < 0)
>> -- 
>> 1.8.3.1
>>