Messages in this thread | | | Date | Thu, 23 Jul 2020 18:08:14 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH v2] mm/page_alloc: fix memalloc_nocma_{save/restore} APIs |
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On Thu, 23 Jul 2020 10:49:02 +0900 js1304@gmail.com wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@lge.com> > > 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.
Whoops.
> Currently, there is just > one user for these APIs and it has a fallback method to prevent actual > problem.
Shouldn't the patch remove the fallback method?
> Second, clearing __GFP_MOVABLE in current_gfp_context() has a side effect > to exclude the memory on the ZONE_MOVABLE for allocation target.
More whoops.
Could we please have a description of the end-user-visible effects of this change? Very much needed when proposing a -stable backport, I think.
d7fefcc8de9147c is over a year old. Why did we only just discover this? This makes one wonder how serious those end-user-visible effects are?
> 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. >
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