On 7/21/20 5:28 AM, [email protected] wrote: > From: Joonsoo Kim <[email protected]> > > Currently, memalloc_nocma_{save/restore} API that prevents CMA area > in page allocation is implemented by using current_gfp_context(). However, > there are two problems of this implementation. > > First, this doesn't work for allocation fastpath. In the fastpath, > original gfp_mask is used since current_gfp_context() is introduced in > order to control reclaim and it is on slowpath. So, CMA area can be > allocated through the allocation fastpath even if > memalloc_nocma_{save/restore} APIs are used. Currently, there is just > one user for these APIs and it has a fallback method to prevent actual > problem. > Second, clearing __GFP_MOVABLE in current_gfp_context() has a side effect > to exclude the memory on the ZONE_MOVABLE for allocation target. > > To fix these problems, this patch changes the implementation to exclude > CMA area in page allocation. Main point of this change is using the > alloc_flags. alloc_flags is mainly used to control allocation so it fits > for excluding CMA area in allocation.
Moreover, the ALLOC_CMA flag already exists for exactly this purpose. > Fixes: d7fefcc8de91 (mm/cma: add PF flag to force non cma alloc) > Cc: <[email protected]> > Signed-off-by: Joonsoo Kim <[email protected]> Reviewed-by: Vlastimil Babka <[email protected]> Thanks!
