Re: [PATCH v6 06/10] userfaultfd/shmem: modify shmem_mfill_atomic_pte to use install_pte()

[Peter Xu]

Axel,

On Mon, May 03, 2021 at 11:07:33AM -0700, Axel Rasmussen wrote:
> In a previous commit, we added the mfill_atomic_install_pte() helper.
> This helper does the job of setting up PTEs for an existing page, to map
> it into a given VMA. It deals with both the anon and shmem cases, as
> well as the shared and private cases.
> 
> In other words, shmem_mfill_atomic_pte() duplicates a case it already
> handles. So, expose it, and let shmem_mfill_atomic_pte() use it
> directly, to reduce code duplication.
> 
> This requires that we refactor shmem_mfill_atomic_pte() a bit:
> 
> Instead of doing accounting (shmem_recalc_inode() et al) part-way
> through the PTE setup, do it afterward. This frees up
> mfill_atomic_install_pte() from having to care about this accounting,
> and means we don't need to e.g. shmem_uncharge() in the error path.
> 
> A side effect is this switches shmem_mfill_atomic_pte() to use
> lru_cache_add_inactive_or_unevictable() instead of just lru_cache_add().
> This wrapper does some extra accounting in an exceptional case, if
> appropriate, so it's actually the more correct thing to use.
> 
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>

(The moving of "ret = -ENOMEM" seems unnecessary, but not a big deal I think)

Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>

Thanks,

-- 
Peter Xu