LU-5263 llite: update ras stride offset

When a read ahead does not reach the end of the region reserved from
ras, we'd set ras::ras_next_readahead back to where we left off; For
stride read ahead, it needs to make sure that the offset is no less
than ras_stride_offset, so that the stride read ahead can work
correctly.

Signed-off-by: Bobi Jam <bobijam.xu@intel.com>
Change-Id: I4996f0d8174fa72ea4ef5994daddc0ab2f922f38
Reviewed-on: http://review.whamcloud.com/11181
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>

diff --git a/lustre/llite/rw.c b/lustre/llite/rw.c
index 8ea255a..4aab3d1 100644 (file)
--- a/lustre/llite/rw.c
+++ b/lustre/llite/rw.c
@@ -474,10 +474,11 @@ static int ll_read_ahead_pages(const struct lu_env *env,
                         /* FIXME: This assertion only is valid when it is for
                          * forward read-ahead, it will be fixed when backward
                          * read-ahead is implemented */
-                        LASSERTF(page_idx > ria->ria_stoff, "Invalid page_idx %lu"
-                                "rs %lu re %lu ro %lu rl %lu rp %lu\n", page_idx,
-                                ria->ria_start, ria->ria_end, ria->ria_stoff,
-                                ria->ria_length, ria->ria_pages);
+                       LASSERTF(page_idx >= ria->ria_stoff,
+                               "Invalid page_idx %lu rs %lu re %lu ro %lu "
+                               "rl %lu rp %lu\n", page_idx,
+                               ria->ria_start, ria->ria_end, ria->ria_stoff,
+                               ria->ria_length, ria->ria_pages);
                         offset = page_idx - ria->ria_stoff;
                         offset = offset % (ria->ria_length);
                         if (offset > ria->ria_pages) {
@@ -538,11 +539,23 @@ int ll_readahead(const struct lu_env *env, struct cl_io *io,
                 ras->ras_window_len = bead->lrr_start + bead->lrr_count -
                                       ras->ras_window_start;
         }
-        /* Reserve a part of the read-ahead window that we'll be issuing */
-        if (ras->ras_window_len) {
-                start = ras->ras_next_readahead;
-                end = ras->ras_window_start + ras->ras_window_len - 1;
-        }
+       /* Reserve a part of the read-ahead window that we'll be issuing */
+       if (ras->ras_window_len > 0) {
+               /*
+                * Note: other thread might rollback the ras_next_readahead,
+                * if it can not get the full size of prepared pages, see the
+                * end of this function. For stride read ahead, it needs to
+                * make sure the offset is no less than ras_stride_offset,
+                * so that stride read ahead can work correctly.
+                */
+               if (stride_io_mode(ras))
+                       start = max(ras->ras_next_readahead,
+                                   ras->ras_stride_offset);
+               else
+                       start = ras->ras_next_readahead;
+               end = ras->ras_window_start + ras->ras_window_len - 1;
+       }
+
         if (end != 0) {
                 unsigned long rpc_boundary;
                 /*