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SubjectRe: [PATCH 1/6] f2fs: optimize get node page readahead part
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Hi,

2013-02-02 (토), 23:51 +0900, Namjae Jeon:
> From: Namjae Jeon <namjae.jeon@samsung.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@samsung.com>
> Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.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,

--
Jaegeuk Kim
Samsung
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