On Tue 05-10-21 11:20:51, Vlastimil Babka wrote: [...] > > --- a/include/linux/gfp.h > > +++ b/include/linux/gfp.h > > @@ -209,7 +209,11 @@ struct vm_area_struct; > > * used only when there is no reasonable failure policy) but it is > > * definitely preferable to use the flag rather than opencode endless > > * loop around allocator. > > - * Using this flag for costly allocations is _highly_ discouraged. > > + * Use of this flag may lead to deadlocks if locks are held which would > > + * be needed for memory reclaim, write-back, or the timely exit of a > > + * process killed by the OOM-killer. Dropping any locks not absolutely > > + * needed is advisable before requesting a %__GFP_NOFAIL allocate. > > + * Using this flag for costly allocations (order>1) is _highly_ discouraged. > > We define costly as 3, not 1. But sure it's best to avoid even order>0 for > __GFP_NOFAIL. Advising order>1 seems arbitrary though? This is not completely arbitrary. We have a warning for any higher order allocation. rmqueue: WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1)); I do agree that "Using this flag for higher order allocations is _highly_ discouraged. > > */ > > #define __GFP_IO ((__force gfp_t)___GFP_IO) > > #define __GFP_FS ((__force gfp_t)___GFP_FS) > > > > > > -- Michal Hocko SUSE Labs
