Re: [PATCH v2 0/5] RDMA, IB: replace __get_free_pages() with kmalloc()

[Leon Romanovsky <leon@kernel.org>]

On Mon, Jul 13, 2026 at 10:17:21AM +0300, Mike Rapoport (Microsoft) wrote:
> This is a (small) part of larger work of replacing page allocator calls
> with kmalloc.
> 
> My initial intention a few month ago was to remove ugly casts [1], but then
> willy pointed out that Linus objected to something like this [2] and it
> looks like more than a decade old technical debt.
> 
> Largely, anything that doesn't need struct page (or a memdesc in the
> future) should just use kmalloc() or kvmalloc() to allocate memory.
> kmalloc() guarantees alignment, physical contiguity and working
> virt_to_phys() and beside nicer API that returns void * on alloc and
> doesn't require to know the allocation size on free, kmalloc() provides
> better debugging capabilities than page allocator.
> 
> Another thing is that touching these allocation sites gives the reviewers
> opportunity to see if a PAGE_SIZE buffer is actually needed or maybe
> another size is appropriate.
> 
> For larger allocations that don't need physically contiguous memory
> kvmalloc() can be a better option that __get_free_pages() because under
> memory pressure it's is easier to allocate several order-0 pages than a
> physically contiguous chunk with the same number of pages.
> 
> And last, but not least, removing needless calls to page allocator should
> help with memdesc (aka project folio) conversion. There will be way less
> places to audit to see if the user was actually using struct page.
> 
> Also in git:
> https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/rdma

Will you also change get_zeroed_page() in RDMA, or should I
prepare a patch?

Thanks

> 
> [1] https://lore.kernel.org/all/20251018093002.3660549-1-rppt@kernel.org/
> [2] https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@mail.gmail.com/ 
> 
> ---
> v2 changes:
> * add comment to keep markers for sites that need "fast and as large as
>   possible" allocation helper
> 
> v1: https://patch.msgid.link/20260630-b4-rdma-v1-0-ab42bcf0de92@kernel.org
> 
> ---
> Mike Rapoport (Microsoft) (5):
>       RDMA/umem: ib_umem_get(): use kmalloc() to allocate page array
>       RDMA/mlx5: replace __get_free_page() with kmalloc()
>       IB/mthca: mthca_reg_user_mr(): use kmalloc() to allocate addresses array
>       IB/mthca: allocate mthca_array memory with kzalloc()
>       IB/rdmavt: use kzalloc() to allocate QPN-map pages
> 
>  drivers/infiniband/core/umem.c                | 5 +++--
>  drivers/infiniband/hw/mlx5/odp.c              | 6 ++++--
>  drivers/infiniband/hw/mthca/mthca_allocator.c | 6 +++---
>  drivers/infiniband/hw/mthca/mthca_provider.c  | 5 +++--
>  drivers/infiniband/sw/rdmavt/qp.c             | 8 ++++----
>  5 files changed, 17 insertions(+), 13 deletions(-)
> ---
> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
> change-id: 20260610-b4-rdma-44625922fe16
> 
> --
> Sincerely yours,
> Mike.
>