Andreas suggested me to get the iozone results after multiple runs.
I don't see any performance issue with the blk bitmap validation changes
now. 



v2.6.24-rc3-35-g2e12044
------------------------
File & VM system latencies in microseconds - smaller is better
--------------------------------------------------------------
Host                 OS   0K File      10K File      Mmap    Prot    Page
                        Create Delete Create Delete  Latency Fault   Fault 
--------- ------------- ------ ------ ------ ------  ------- -----   ----- 
elm3a150. Linux 2.6.24-   28.8   24.9   90.3   52.2    13.4K 1.796 3.00000
elm3a150. Linux 2.6.24-   29.2   25.1   90.3   52.0    13.4K 1.829 3.00000
elm3a150. Linux 2.6.24-   28.7   24.8   90.2   51.2    13.3K 1.971 3.00000


v2.6.24-rc3-35-g2e12044 + with block bitmap patch 
--------------------------------


File & VM system latencies in microseconds - smaller is better
--------------------------------------------------------------
Host                 OS   0K File      10K File      Mmap    Prot    Page
                        Create Delete Create Delete  Latency Fault   Fault 
--------- ------------- ------ ------ ------ ------  ------- -----   ----- 
elm3a150. Linux 2.6.24-   28.5   24.7   89.3   52.1    13.4K 1.785 3.00000
elm3a150. Linux 2.6.24-   28.7   24.9   89.4   52.2    13.3K 1.792 3.00000
elm3a150. Linux 2.6.24-   29.1   24.8   90.1   52.4    13.3K 1.779 3.00000
elm3a150. Linux 2.6.24-   29.2   24.9   90.4   52.0    13.9K 1.848 3.00000


iozones results are attached.
----------------------------