[PATCH 00/15] mm/hugetlb: various fixes

["David Hildenbrand (Arm)" <david@kernel.org>]

These fixes almost finished me.

Oh. My. God, hugetlb, what have you become.

And I am not talking about good old hugetlb. I am talking about all of the
things we slapped on top of it over the years, including MAP_PRIVATE,
reservation, UFFD, accounting and much more. I mean, I kept complaining
about all that in the past, but I just had an 2 day-long reminder from
hell.

And don't get me started on some of the proposed AI fixes. Dear lord.
There is a reason why I am the author on most of these fixes. And I
try to not swear on the mailing list.

Hey, at least huge PMD sharing was not involved this time, great
success!

Anyhow, nothing here is super urgent IMHO. Just a lot of unpleasant
things and corner cases. Most of the issues reported by Anthropic, some
found by me while poking at things.

Two bigger changes as RFC. One of them documents some remaining
problems, one of both being a hard nut to crack.

I have some more complicated lower priority, hard to solve things
leftover on the hugetlb front (besides some fixes that are already on the
list), maybe I'll report them to hugetlb maintainers to share some of
the "fun". ;)

I threw some tests at it, but there are just too many combinations and
corner cases.

Next, likely we want a kernel config to disable MAP_PRIVATE and start
deprecating it. It's simply unbearable.

I won't pretend that I understood all the details of reservation and
accounting, even rewriting some of the comments took me ages. If any
fixes here go into the wrong direction, I'm happy if someone wants to
take over this series, I tried to get the heavy lifting done.

I guess, have fun reviewing? :)

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
Chris Mason (3):
      hugetlbfs: do not grow a sealed file in mmap()
      mm/hugetlb: keep surplus folios that are reserved
      mm/hugetlb: fix reservation leak on min_size= mounts

David Hildenbrand (Arm) (10):
      hugetlbfs: fix integer overflow in fallocate()
      mm/hugetlb: compare against persistent count when freeing lowmem folios
      mm/hugetlb: preserve reservations when shrinking on HIGHMEM
      mm/hugetlb: account temporary folios separately
      mm/hugetlb: fix mremap() racing with page migration
      mm/hugetlb: serialize page-cache allocations with truncation
      mm/memfd: recheck the page cache before allocating a hugetlb folio
      mm/hugetlb: count again if the reserve map shrank
      RFC: mm/hugetlb: account restored reservations before freeing folios
      RFC: mm/hugetlb: delay anon folio rmap removal until after the TLB flush

Josef Bacik (2):
      mm/hugetlb: keep surplus folios when the pool shrinks
      hugetlbfs: fix unmapping folios from private VMAs

 Documentation/mm/hugetlbfs_reserv.rst |  30 +--
 arch/s390/include/asm/tlb.h           |   5 +-
 fs/hugetlbfs/inode.c                  |  36 +++-
 include/asm-generic/tlb.h             |   5 +-
 include/linux/hugetlb.h               |  24 +++
 mm/hugetlb.c                          | 388 ++++++++++++++++++++++------------
 mm/hugetlb_internal.h                 |  11 +
 mm/hugetlb_sysfs.c                    |   2 +-
 mm/memfd.c                            |  17 ++
 mm/mmu_gather.c                       |  14 +-
 10 files changed, 361 insertions(+), 171 deletions(-)

---

base-commit: 65ba8f34ec886ec72b2c07ddc8cf3d815c32869d

change-id: 20261027-fixes_hugetlb-2c4f02ff6304

--

Cheers,

David