On Wed, Sep 15, 2021 at 10:52:40PM +0800, Qi Zheng wrote: > I am going to split this patch series as follows: > > 1. Introduce the new dummy APIs, which is an empty implementation. > But I will explain its semantics. > 2. Merge #6, #7 and #8, and call these dummy APIs in any necessary > location, and split some special cases into single patches, such as > pagefault and gup, etc. So that we can explain in more detail the > concurrency in these cases. For example, we don't need to hold any > pte_refcount in the fast path in gup on the x86_64 platform. Because > the PTE page can't be freed after the local CPU interrupt is closed > in the fast path in gup. > 3. Introduce CONFIG_FREE_USER_PTE and implement these empty dummy APIs. > 4. Add a description document. > > And I try to add a function that combines pte_offset_map() and > pte_try_get(). Maybe the func name is pte_try_map() recommended by > Jason, or keep the pte_offset_map() unchanged? It is part of the transformation, add a pte_try_map()/pte_undo_try_map() and replace all the pte_offset_map() callsites that can use the new API with it. The idea was that try_map would incorporate the pmd_trans_unstable/etc mess so searching for trans_unstable is a good place to start finding candidates. Some are simple, some are tricky. When you get to step 3 you just change pte_try_map() and the callsites don't need changing. Jason
