On Thu 27-01-22 10:49:42, Christoph Hellwig wrote:
> On Thu, Jan 27, 2022 at 10:47:37AM +0100, Jan Kara wrote:
> > On Wed 26-01-22 16:50:35, Christoph Hellwig wrote:
> > > Nothing prevents a file system or userspace opener of the block device
> > > from redirtying the page right afte sync_blockdev returned.  Fortunately
> > > data in the page cache during a block device change is mostly harmless
> > > anyway.
> > > 
> > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > 
> > My understanding was these warnings are there to tell userspace it is doing
> > something wrong. Something like the warning we issue when DIO races with
> > buffered IO... I'm not sure how useful they are but I don't see strong
> > reason to remove them either...
> 
> Well, it is not just a warning, but also fails the command.  With some of
> the reduced synchronization blktests loop/002 can hit them pretty reliably.

I see. I guess another place where using mapping->invalidate_lock would be
good to avoid these races... So maybe something like attached patch?

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