On Fri 25-05-18 08:17:15, Dave Chinner wrote: > On Thu, May 24, 2018 at 01:43:41PM +0200, Michal Hocko wrote: [...] > > +FS/IO code then simply calls the appropriate save function right at the > > +layer where a lock taken from the reclaim context (e.g. shrinker) and > > +the corresponding restore function when the lock is released. All that > > +ideally along with an explanation what is the reclaim context for easier > > +maintenance. > > This paragraph doesn't make much sense to me. I think you're trying > to say that we should call the appropriate save function "before > locks are taken that a reclaim context (e.g a shrinker) might > require access to." > > I think it's also worth making a note about recursive/nested > save/restore stacking, because it's not clear from this description > that this is allowed and will work as long as inner save/restore > calls are fully nested inside outer save/restore contexts. Any better? -FS/IO code then simply calls the appropriate save function right at the -layer where a lock taken from the reclaim context (e.g. shrinker) and -the corresponding restore function when the lock is released. All that -ideally along with an explanation what is the reclaim context for easier -maintenance. +FS/IO code then simply calls the appropriate save function before any +lock shared with the reclaim context is taken. The corresponding +restore function when the lock is released. All that ideally along with +an explanation what is the reclaim context for easier maintenance. + +Please note that the proper pairing of save/restore function allows nesting +so memalloc_noio_save is safe to be called from an existing NOIO or NOFS scope. What about __vmalloc(GFP_NOFS) ============================== -- Michal Hocko SUSE Labs
