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    Subject[PATCH 12/14] staging/lustre/llite: update ras window correctly
    Date
    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.

    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
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