On Wed 13-12-17 07:39:30, Tejun Heo wrote: > Hello, > > On Wed, Dec 13, 2017 at 12:00:04PM +0100, Jan Kara wrote: > > OK, but this effectively prevents writeback from sync_inodes_sb() to ever > > make inode switch wbs. Cannot that be abused in some way like making sure > > writeback of our memcg is "invisible" by forcing it out using sync(2)? It > > just looks a bit dangerous to me... > > That's true. There are a couple mitigating factors tho. > > * While it can delay switching during sync(2), it'll all still be > recorded and the switch will happen soon if needed. > > * sync(2) is hugely disruptive with or without this and can easily be > used to DOS the whole system. People are working on restricting the > blast radius of sync(2) to mitigate this problem, which most likely > make this a non-problem too. > > If you can think of a better solution, I'm all ears. After some thinking about this I don't have a better solution. So you can add: Acked-by: Jan Kara <jack@xxxxxxx> Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
