LU-8683 readahead: update ras window correctly

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.

Lustre-change: http://review.whamcloud.com/17343
Lustre-commit: 88ef5af0bed93c88984c226db755d07601aef60f

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: Iba6e51f12ac4d00548cc99b7bd423502b754db13
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Reviewed-on: http://review.whamcloud.com/23032
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-by: Jinshan Xiong <jinshan.xiong@intel.com>

diff --git a/lustre/llite/rw.c b/lustre/llite/rw.c
index 7ab5a39..79ca522 100644 (file)
--- a/lustre/llite/rw.c
+++ b/lustre/llite/rw.c
@@ -802,12 +802,19 @@ 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