From Bugzilla Helper:
User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET 
CLR 1.1.4322)

Description of problem:
BLKFLSBUF ioctl can cause other reads to fail

In the TC, it is doing randio's(read and verify write). Due to
verify-write, I/Os are happening on the block device(In the old raw
interface IOCTLs are not allowed on raw device). In reopen_dev()
function(randio.c), it is issueing BLKFLSBUF ioctl, and is causing  
the other reads to fail.


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


How reproducible:
Always

Steps to Reproduce:
To reproduce the problem, run the following scripts in parllal.

1) script1.sh
     while [ 0 ]
     do
        dd if=/dev/sdm1 of=/dev/null bs=1M count=100
     done


2) script2.sh
     while [ 0 ]
     do
        blockdev --flushbufs /dev/sdm1
     done

Additional info:

If the caller of invalidate_complete_page() is passing a page with a 
reference of 2, he is the only one that currently has a reference to 
it. And that's the only case where it's ok to mark the page not-
uptodate.

The problem is easily reproducable and the problem is actually quite 
obvious once you found out where things went wrong. I think it should 
be committed to GA right away.