Description of problem:
"dd" command fails to read the block device while mounting/unmounting the device

Version-Release number of selected component (if applicable):
RHEL4 U1

How reproducible:
Always

Steps to Reproduce:
    Please run the following scripts in parallel.

   1) script1.sh

     while :
     do
           dd if=/dev/sdb1 of=/dev/null bs=1M count=100
     done


   2) script2.sh

     while :
     do
           umount /mnt/work1
           mount -t ext3 /dev/sdb1 /mnt/work1
     done
  
Actual results:
ããdd command fails.
  The following messages are output.
      dd: reading `/dev/sdb1': Input/output error
      0+1 records in
      0+1 records out

Expected results:
ããdd command does not fail.
  The following messages are output.
      100+0 records in
      100+0 records out

Additional info:
  The following change of bitkeeper seems to be related.

  http://lin ux.bkbits.net:8080/linux-2.6/patch.39.96