On Wed 25-04-18 08:43:32, Mikulas Patocka wrote: > > > On Tue, 24 Apr 2018, Michal Hocko wrote: > > > On Tue 24-04-18 19:17:12, Mikulas Patocka wrote: > > > > > > > > > On Tue, 24 Apr 2018, Michal Hocko wrote: > > > > > > > On Wed 25-04-18 00:18:40, Richard Weinberger wrote: > > > > > Am Dienstag, 24. April 2018, 21:28:03 CEST schrieb Michal Hocko: > > > > > > > Also only for debugging. > > > > > > > Getting rid of vmalloc with GFP_NOFS in UBIFS is no big problem. > > > > > > > I can prepare a patch. > > > > > > > > > > > > Cool! > > > > > > > > > > > > Anyway, if UBIFS has some reclaim recursion critical sections in general > > > > > > it would be really great to have them documented and that is where the > > > > > > scope api is really handy. Just add the scope and document what is the > > > > > > recursion issue. This will help people reading the code as well. Ideally > > > > > > there shouldn't be any explicit GFP_NOFS in the code. > > > > > > > > > > So in a perfect world a filesystem calls memalloc_nofs_save/restore and > > > > > always uses GFP_KERNEL for kmalloc/vmalloc? > > > > > > > > Exactly! And in a dream world those memalloc_nofs_save act as a > > > > documentation of the reclaim recursion documentation ;) > > > > -- > > > > Michal Hocko > > > > SUSE Labs > > > > > > BTW. should memalloc_nofs_save and memalloc_noio_save be merged into just > > > one that prevents both I/O and FS recursion? > > > > Why should FS usage stop IO altogether? > > Because the IO may reach loop and loop may redirect it to the same > filesystem that is running under memalloc_nofs_save and deadlock. So what is the difference with the current GFP_NOFS? > > > memalloc_nofs_save allows submitting bios to I/O stack and the bios > > > created under memalloc_nofs_save could be sent to the loop device and the > > > loop device calls the filesystem... > > > > Don't those use NOIO context? > > What do you mean? That the loop driver should make sure it will not recurse. The scope API doesn't add anything new here. -- Michal Hocko SUSE Labs
