fs: page cache wrongly left invalidated after revalidate_disk

[MITSUNARI Shigeo]

Hi, 

We found that bdev->bd_invalidated was left set once revalidate_disk() 
is called, which results in page cache flush every time that device 
is open. 

Specifically, we found this problem in MD block device.  Once we 
resize a MD device, mdadm --monitor periodically flush all page cache 
for that device every 60 or 1000 seconds when it opens the device. 

This bug lies since at least 3.2.0 till the latest kernel(3.6.2). 
Patch is attached. 

Anyone please review this?  Thanks in advance.

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