On Mon, 21 Sep 2015 11:52:38 +0100 Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote: > __GFP_WAIT was used to signal that the caller was in atomic context and > could not sleep. Now it is possible to distinguish between true atomic > context and callers that are not willing to sleep. The latter should clear > __GFP_DIRECT_RECLAIM so kswapd will still wake. As clearing __GFP_WAIT > behaves differently, there is a risk that people will clear the wrong > flags. This patch renames __GFP_WAIT to __GFP_RECLAIM to clearly indicate > what it does -- setting it allows all reclaim activity, clearing them > prevents it. We have quite a history of remote parts of the kernel using weird/wrong/inexplicable combinations of __GFP_ flags. I tend to think that this is because we didn't adequately explain the interface. And I don't think that gfp.h really improved much in this area as a result of this patchset. Could you go through it some time and decide if we've adequately documented all this stuff? GFP_ATOMIC vs GFP_NOWAIT? GFP_USER vs GFP_HIGHUSER? When should I use GFP_HIGHUSER_MOVABLE instead? Why isn't there a GFP_USER_MOVABLE? What's GFP_IOFS? GFP_RECLAIM_MASK through GFP_SLAB_BUG_MASK are mm-internal, but look the same as the exported interface definitions. __GFP_MOVABLE is documented twice, the second in an odd place. etcetera. It's rather unclear which symbols are part of the exported interface and which are "mm internal only". -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>