struct iam_container {
    ...
        /*
         * read-write lock protecting index consistency.
         */
        struct rw_semaphore     ic_sem;   <<<<<<
        struct dynlock       ic_tree_lock;
        /* Protect ic_idle_bh */
        struct mutex         ic_idle_mutex;
     ...
};

 2    234  lustre/osd-ldiskfs/osd_iam.c <<iam_container_init>>
             init_rwsem(&c->ic_sem);

 3    622  lustre/osd-ldiskfs/osd_iam.c <<iam_container_write_lock>>
             down_write(&ic->ic_sem);
   4    627  lustre/osd-ldiskfs/osd_iam.c <<iam_container_write_unlock>>
             up_write(&ic->ic_sem);
   5    632  lustre/osd-ldiskfs/osd_iam.c <<iam_container_read_lock>>
             down_read(&ic->ic_sem);
   6    637  lustre/osd-ldiskfs/osd_iam.c <<iam_container_read_unlock>>
             up_read(&ic->ic_sem);