Re: [PATCH 3/3] xfsqa: xfs_check can see stale cached blocks

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Tue, Jan 19, 2010 at 08:03:12PM +1100, Dave Chinner wrote:
> Test 017 is consistently failing now because the xfs_check uses
> buffered IO to read the block device and 017 runs xfs_check ona
> remount,ro filesystem. Hence the block device cache is never
> invalidated (the unmount path does this) and so xfs_check can see
> stale blocks from previous invocations instead of what is really on
> disk at the time it is run.
> 
> Manually trash the page cache before running xfs_check to ensure
> that the blockdev cache is clean and we don't get false errors
> from stale blocks.

I don't think this is correct.  We need to provide this synchronization
from kernel land.  IIRC Al even has a patch towards this in his tree,
can't point you to it to try it because his tree on kernel.org seems
messed up right now.