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SubjectRe: [RESEND PATCH] fs/buffer.c: exit if already confirmed page has dirty and writeback buffers
On Tue 05-11-13 18:02:03, Gu Zheng wrote:
> Stop the loop of iterating bh if we have confirmed page
> has dirty and writeback buffers.
Thanks for the patch. What I'm somewhat missing here is a motivation of
the patch. For the common case where blocksize == pagesize this is a noop
(only adds some code). For the case where blocksize < pagesize we can
possibly save checking some buffers but how common is that going be? Does
that minimal speed up outweight the cost of additional check / code
complication?

Honza

>
> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
> ---
> fs/buffer.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 6024877..519cc5c 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -112,7 +112,7 @@ void buffer_check_dirty_writeback(struct page *page,
> *dirty = true;
>
> bh = bh->b_this_page;
> - } while (bh != head);
> + } while ((bh != head) && !(*writeback && *dirty));
> }
> EXPORT_SYMBOL(buffer_check_dirty_writeback);
>
> --
> 1.7.7
>
> --
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--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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