Re: invalidate the buffer heads of a block device

[Jan Kara <jack@suse.cz>]

On Tue 30-09-14 10:11:32, Thanos Makatos wrote:
> >   Yes, "unknown" process can read data back into pagecache while your ioctl
> > is running thus undoing your work. But if the writes are already visible on the
> > *device* at the moment you run the ioctl, then "unknown" process will just
> > fetch new data and everything is fine... If you need to evict page cache
> > *before* new data is visible on the device, then you need to suspend the
> > device first so that it doesn't serve any IO, then evict page cache, then make
> > new data visible on the device, and finally resume the device.
> > Suspend/resume of the device can be handled by device mapper (it does
> > these tricks when you are changing topology of the device on the fly).
> 
> The writes will be visible to the device *before* the ioctl runs so I
> have one thing less to worry about!
> 
> Regarding extending the ioctl to invalidate the page cache, do you  have
> any suggestions where I could start looking?
  You just need to call invalidate_inode_pages2(). That is going to do all
you need.

> Would such a new ioctl have any chance to be accepted upstream?
  I believe a possibility for a file to be fully flushed from page cache is
useful at times and if you present well your usecase there are reasonable
chances it will get accepted upstream. 

								Honza
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR