linux-kernel - Re: [PATCH 1/6] f2fs: optimize get node page readahead part

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Date:	Mon, 4 Feb 2013 11:06:45 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	jaegeuk.kim@...sung.com
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Amit Sahrawat <a.sahrawat@...sung.com>
Subject: Re: [PATCH 1/6] f2fs: optimize get node page readahead part

2013/2/4, Jaegeuk Kim <jaegeuk.kim@...sung.com>:
> Hi,
>
> 2013-02-02 (토), 23:51 +0900, Namjae Jeon:
>> From: Namjae Jeon <namjae.jeon@...sung.com>
>>
>> We can remove the call to find_get_page to get a page from the cache
>> and check for up-to-date, instead we can make use of grab_cache_page
>> part itself to fetch the page from the cache.
>> So, removing the call and moving the PageUptodate at proper place, also
>> taken care of moving the lock_page condition in the page_hit part.
>>
>> Signed-off-by: Namjae Jeon <namjae.jeon@...sung.com>
>> Signed-off-by: Amit Sahrawat <a.sahrawat@...sung.com>
>> ---
>>  fs/f2fs/node.c |   10 ++++------
>>  1 file changed, 4 insertions(+), 6 deletions(-)
>>
>> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
>> index 33fa6d5..723185b 100644
>> --- a/fs/f2fs/node.c
>> +++ b/fs/f2fs/node.c
>> @@ -920,15 +920,12 @@ struct page *get_node_page_ra(struct page *parent,
>> int start)
>>  	if (!nid)
>>  		return ERR_PTR(-ENOENT);
>>
>> -	page = find_get_page(mapping, nid);
>> -	if (page && PageUptodate(page))
>> -		goto page_hit;
>> -	f2fs_put_page(page, 0);
>> -
>
> The reason why we use this is to avoid the lock overhead.
> This is a readahead flow, and we don't need to care about real
> existence. Let's get and check the status of the page without any locks.
> Thanks,
Yes, Agreed. I will chceck more about this.
Thanks a lot!
>
> --
> Jaegeuk Kim
> Samsung
>
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