LU-12328 flr: preserve last read mirror

[fs/lustre-release.git] / lustre / lov / lov_io.c

diff --git a/lustre/lov/lov_io.c b/lustre/lov/lov_io.c
index 2fa95f5..415a91b 100644 (file)
--- a/lustre/lov/lov_io.c
+++ b/lustre/lov/lov_io.c
@@ -390,15 +390,31 @@ static int lov_io_mirror_init(struct lov_io *lio, struct lov_object *obj,
            /* reset the mirror index if layout has changed */
            lio->lis_mirror_layout_gen != obj->lo_lsm->lsm_layout_gen) {
                lio->lis_mirror_layout_gen = obj->lo_lsm->lsm_layout_gen;
-               index = lio->lis_mirror_index = comp->lo_preferred_mirror;
+               index = lio->lis_mirror_index = comp->lo_last_read_mirror;
        } else {
                index = lio->lis_mirror_index;
                LASSERT(index >= 0);
 
                /* move mirror index to the next one */
-               index = (index + 1) % comp->lo_mirror_count;
+               spin_lock(&comp->lo_write_lock);
+               if (index == comp->lo_last_read_mirror) {
+                       do {
+                               index = (index + 1) % comp->lo_mirror_count;
+                               if (comp->lo_mirrors[index].lre_valid)
+                                       break;
+                       } while (index != comp->lo_last_read_mirror);
+
+                       /* reset last read replica so that other threads can
+                        * take advantage of our retries. */
+                       comp->lo_last_read_mirror = index;
+               } else {
+                       /* last read index was moved by other thread */
+                       index = comp->lo_last_read_mirror;
+               }
+               spin_unlock(&comp->lo_write_lock);
        }
 
+       /* make sure the mirror chosen covers the extent we'll read */
        for (i = 0; i < comp->lo_mirror_count; i++) {
                struct lu_extent ext = { .e_start = lio->lis_pos,
                                         .e_end   = lio->lis_pos + 1 };