LU-8900 snapshot: check write barrier before modification

[fs/lustre-release.git] / lustre / target / barrier.c

diff --git a/lustre/target/barrier.c b/lustre/target/barrier.c
index 3710908..e52d303 100644 (file)
--- a/lustre/target/barrier.c
+++ b/lustre/target/barrier.c
@@ -237,6 +237,51 @@ void barrier_fini(void)
        LASSERT(list_empty(&barrier_instance_list));
 }
 
+bool barrier_entry(struct dt_device *key)
+{
+       struct barrier_instance *barrier;
+       bool entered = false;
+       ENTRY;
+
+       barrier = barrier_instance_find(key);
+       if (unlikely(!barrier))
+               /* Fail open */
+               RETURN(true);
+
+       read_lock(&barrier->bi_rwlock);
+       if (likely(barrier->bi_status != BS_FREEZING_P1 &&
+                  barrier->bi_status != BS_FREEZING_P2 &&
+                  barrier->bi_status != BS_FROZEN) ||
+           cfs_time_beforeq(barrier->bi_deadline, cfs_time_current_sec())) {
+               percpu_counter_inc(&barrier->bi_writers);
+               entered = true;
+       }
+       read_unlock(&barrier->bi_rwlock);
+
+       barrier_instance_put(barrier);
+       return entered;
+}
+EXPORT_SYMBOL(barrier_entry);
+
+void barrier_exit(struct dt_device *key)
+{
+       struct barrier_instance *barrier;
+
+       barrier = barrier_instance_find(key);
+       if (likely(barrier)) {
+               percpu_counter_dec(&barrier->bi_writers);
+
+               /* Avoid out-of-order execution the decreasing inflight
+                * modifications count and the check of barrier status. */
+               smp_mb();
+
+               if (unlikely(barrier->bi_status == BS_FREEZING_P1))
+                       wake_up_all(&barrier->bi_waitq);
+               barrier_instance_put(barrier);
+       }
+}
+EXPORT_SYMBOL(barrier_exit);
+
 int barrier_handler(struct dt_device *key, struct ptlrpc_request *req)
 {
        struct ldlm_gl_barrier_desc *desc;