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* [PATCH v2 0/5] RDMA, IB: replace __get_free_pages() with kmalloc()
@ 2026-07-13  7:17 Mike Rapoport (Microsoft)
  2026-07-13  7:17 ` [PATCH v2 1/5] RDMA/umem: ib_umem_get(): use kmalloc() to allocate page array Mike Rapoport (Microsoft)
                   ` (4 more replies)
  0 siblings, 5 replies; 6+ messages in thread
From: Mike Rapoport (Microsoft) @ 2026-07-13  7:17 UTC (permalink / raw)
  To: Jason Gunthorpe, Leon Romanovsky
  Cc: Dennis Dalessandro, Mike Rapoport, linux-kernel, linux-mm,
	linux-rdma

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

[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.



^ permalink raw reply	[flat|nested] 6+ messages in thread
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Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-07-13  7:17 [PATCH v2 0/5] RDMA, IB: replace __get_free_pages() with kmalloc() Mike Rapoport (Microsoft)
2026-07-13  7:17 ` [PATCH v2 1/5] RDMA/umem: ib_umem_get(): use kmalloc() to allocate page array Mike Rapoport (Microsoft)
2026-07-13  7:17 ` [PATCH v2 2/5] RDMA/mlx5: replace __get_free_page() with kmalloc() Mike Rapoport (Microsoft)
2026-07-13  7:17 ` [PATCH v2 3/5] IB/mthca: mthca_reg_user_mr(): use kmalloc() to allocate addresses array Mike Rapoport (Microsoft)
2026-07-13  7:17 ` [PATCH v2 4/5] IB/mthca: allocate mthca_array memory with kzalloc() Mike Rapoport (Microsoft)
2026-07-13  7:17 ` [PATCH v2 5/5] IB/rdmavt: use kzalloc() to allocate QPN-map pages Mike Rapoport (Microsoft)

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