Re: [PATCH 1/2] fs: optimize mpage_readpage()

[Borislav Petkov]

From: Changli Gao <xiaosuo@xxxxxxxxx>
Date: Sat, May 29, 2010 at 09:18:46AM +0800

> optimize mpage_readpage()
> 
> we don't need to initialize bio, and pass it to do_mpage_readpage() as
> parameter, as it is returned by do_mpage_readpage().
> 
> Signed-off-by: Changli Gao <xiaosuo@xxxxxxxxx>
> ----
>  fs/mpage.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> diff --git a/fs/mpage.c b/fs/mpage.c
> index fd56ca2..94ff0d1 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -409,14 +409,14 @@ EXPORT_SYMBOL(mpage_readpages);
>   */
>  int mpage_readpage(struct page *page, get_block_t get_block)
>  {
> -	struct bio *bio = NULL;
> +	struct bio *bio;
>  	sector_t last_block_in_bio = 0;
>  	struct buffer_head map_bh;
>  	unsigned long first_logical_block = 0;
>  
>  	map_bh.b_state = 0;
>  	map_bh.b_size = 0;
> -	bio = do_mpage_readpage(bio, page, 1, &last_block_in_bio,
> +	bio = do_mpage_readpage(NULL, page, 1, &last_block_in_bio,
>  			&map_bh, &first_logical_block, get_block);
>  	if (bio)
>  		mpage_bio_submit(READ, bio);

Nope, I don't think that's a good idea.

On the one hand, this is a trick to shut up gcc:

fs/mpage.c: In function âmpage_readpageâ:
fs/mpage.c:419: warning: âbioâ is used uninitialized in this function

and, on the other hand, make sure bio is NULL and not some random stack
value since bio is explicitly checked for NULL in do_mpage_readpage().

-- 
Regards/Gruss,
    Boris.
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