Messages in this thread | | | Date | Wed, 3 Jun 2015 15:42:04 +0200 | From | Michal Hocko <> | Subject | Re: [RFC 0/2] mapping_gfp_mask from the page fault path |
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On Wed 03-06-15 22:04:22, Tetsuo Handa wrote: [...] > Michal Hocko wrote: > > Initialize the default to (mapping_gfp_mask | GFP_IOFS) because this > > should be safe from the page fault path normally. Why do we care > > about mapping_gfp_mask at all then? Because this doesn't hold only > > reclaim protection flags but it also might contain zone and movability > > restrictions (GFP_DMA32, __GFP_MOVABLE and others) so we have to respect > > those. > > [2/2] says that mapping_gfp_mask(mapping) might contain bits which are not > in !GFP_KERNEL. If we do > > GFP_KERNEL & mapping_gfp_mask(mapping) > > we will drop such bits and will cause problems.
No we won't.
> Thus, "GFP_KERNEL" > in patch [1/1] should be replaced with "mapping_gfp_mask(mapping)" than > "GFP_KERNEL & mapping_gfp_mask(mapping)" ?
Those gfp_masks are for LRU handling and that is GFP_KERNEL by default. We only need to drop those which are not compatible with mapping_gfp_mask. We do not care about __GFP_MOVABLE, GFP_DMA32 etc... -- Michal Hocko SUSE Labs
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