[PATCH 0/5] s390/char: replace page allocator calls with k[mz]alloc()

["Mike Rapoport (Microsoft)" <rppt@kernel.org>]

This the next episode of conversion of page allocator calls to kmalloc
family :)

This series covers s390 character drivers other than SCLP.

= tl;dr cover letter copied from the previous posts:

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.

The patches are deliberately kept small, so that every conversion can be
reviewed, and if needed reverted, on its own.

Also in git:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git gfp-to-kmalloc/s390-char

[1] https://lore.kernel.org/all/20251018093002.3660549-1-rppt@kernel.org/
[2] https://lore.kernel.org/all/CA+55aFwp4iy4rtX2gE2WjBGFL=NxMVnoFeHqYa2j1dYOMMGqxg@mail.gmail.com/

---
Mike Rapoport (Microsoft) (5):
      s390/zcore: Replace __get_free_page() with kmalloc()
      s390/vmur: Replace __get_free_page() with kmalloc()
      s390/vmlogrdr: Replace get_zeroed_page() with kzalloc()
      s390/uvdevice: Replace get_zeroed_page() with kzalloc()
      s390/hmcdrv: Replace page allocator calls with k[mz]alloc()

 drivers/s390/char/diag_ftp.c     |  5 +++--
 drivers/s390/char/hmcdrv_cache.c | 18 +++++++++---------
 drivers/s390/char/hmcdrv_ftp.c   | 14 +++++++-------
 drivers/s390/char/uvdevice.c     |  4 ++--
 drivers/s390/char/vmlogrdr.c     |  4 ++--
 drivers/s390/char/vmur.c         |  8 ++++----
 drivers/s390/char/zcore.c        |  8 ++++----
 7 files changed, 31 insertions(+), 30 deletions(-)
---
base-commit: 6628e7d4c6b25c8d18f1345e3a20d21829aae7e4
change-id: 20260907-s390-char-ready-29b03a1bf781

--
Sincerely yours,
Mike.