On Wed 05-04-17 13:39:16, Vlastimil Babka wrote: > On 04/05/2017 01:36 PM, Richard Weinberger wrote: > > Michal, > > > > Am 05.04.2017 um 13:31 schrieb Michal Hocko: > >> On Wed 05-04-17 09:47:00, Vlastimil Babka wrote: > >>> Nandsim has own functions set_memalloc() and clear_memalloc() for robust > >>> setting and clearing of PF_MEMALLOC. Replace them by the new generic helpers. > >>> No functional change. > >> > >> This one smells like an abuser. Why the hell should read/write path > >> touch memory reserves at all! > > > > Could be. Let's ask Adrian, AFAIK he wrote that code. > > Adrian, can you please clarify why nandsim needs to play with PF_MEMALLOC? > > I was thinking about it and concluded that since the simulator can be > used as a block device where reclaimed pages go to, writing the data out > is a memalloc operation. Then reading can be called as part of r-m-w > cycle, so reading as well. But it would be great if somebody more > knowledgeable confirmed this. then this deserves a big fat comment explaining all the details, including how the complete depletion of reserves is prevented. -- Michal Hocko SUSE Labs
