> -----Original Message----- > From: Song Bao Hua (Barry Song) > Sent: Tuesday, December 22, 2020 3:03 PM > To: 'Vitaly Wool' <vitaly.wool@xxxxxxxxxxxx> > Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>; Minchan Kim <minchan@xxxxxxxxxx>; Mike > Galbraith <efault@xxxxxx>; LKML <linux-kernel@xxxxxxxxxxxxxxx>; linux-mm > <linux-mm@xxxxxxxxx>; Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>; > NitinGupta <ngupta@xxxxxxxxxx>; Sergey Senozhatsky > <sergey.senozhatsky.work@xxxxxxxxx>; Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx>; tiantao (H) <tiantao6@xxxxxxxxxxxxx> > Subject: RE: [PATCH] zsmalloc: do not use bit_spin_lock > > > > I'm still not convinced. Will kmap what, src? At this point src might become > just a bogus pointer. > > As long as the memory is still there, we can kmap it by its page struct. But > if > it is not there anymore, we have no way. > > > Why couldn't the object have been moved somewhere else (due to the compaction > mechanism for instance) > > at the time DMA kicks in? > > So zs_map_object() will guarantee the src won't be moved by holding those > preemption-disabled lock? > If so, it seems we have to drop the MOVABLE gfp in zswap for zsmalloc case? > Or we can do get_page() to avoid the movement of the page. > > > > > > > > ~Vitaly > > > > Thanks > Barry
