Re: [PATCH 12/14] staging/lustre/llite: update ras window correctly

[James Simmons <jsimmons@infradead.org>]

> From: Bobi Jam <bobijam.xu@intel.com>
> 
> When stride-RA hit case miss, we only reset normal sequential
> read-ahead window, but not reset the stride IO to avoid the overhead
> of re-detecting stride IO. While when the normal RA window is set
> to not insect with the stride-RA window, when we try to increase
> the stride-RA window length later, the presumption does not hold.
> 
> This patch resets the stride IO as well in this case.

Reviewed-by: James Simmons <jsimmons@infradead.org>
 
> Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
> Reviewed-on: http://review.whamcloud.com/23032
> Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8683
> Reviewed-by: wangdi <di.wang@intel.com>
> Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>
> Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
> ---
>  drivers/staging/lustre/lustre/llite/rw.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/lustre/lustre/llite/rw.c b/drivers/staging/lustre/lustre/llite/rw.c
> index d2515a8..e34017d 100644
> --- a/drivers/staging/lustre/lustre/llite/rw.c
> +++ b/drivers/staging/lustre/lustre/llite/rw.c
> @@ -809,13 +809,20 @@ static void ras_update(struct ll_sb_info *sbi, struct inode *inode,
>  		if (ra_miss) {
>  			if (index_in_stride_window(ras, index) &&
>  			    stride_io_mode(ras)) {
> -				/*If stride-RA hit cache miss, the stride dector
> -				 *will not be reset to avoid the overhead of
> -				 *redetecting read-ahead mode
> -				 */
>  				if (index != ras->ras_last_readpage + 1)
>  					ras->ras_consecutive_pages = 0;
>  				ras_reset(inode, ras, index);
> +
> +				/* If stride-RA hit cache miss, the stride
> +				 * detector will not be reset to avoid the
> +				 * overhead of redetecting read-ahead mode,
> +				 * but on the condition that the stride window
> +				 * is still intersect with normal sequential
> +				 * read-ahead window.
> +				 */
> +				if (ras->ras_window_start <
> +				    ras->ras_stride_offset)
> +					ras_stride_reset(ras);
>  				RAS_CDEBUG(ras);
>  			} else {
>  				/* Reset both stride window and normal RA
> -- 
> 2.7.4
> 
>