Use killable vma write locking in most places

Now that we have vma_start_write_killable() we can replace most of the
vma_start_write() calls with it, improving reaction time to the kill
signal.

There are several places which are left untouched by this patchset:

1. free_pgtables() because function should free page tables even if a
fatal signal is pending.

2. userfaultd code, where some paths calling vma_start_write() can
handle EINTR and some can't without a deeper code refactoring.

3. mpol_rebind_mm() which is used by cpusset controller for migrations
and operates on a remote mm. Incomplete operations here would result
in an inconsistent cgroup state.

4. vm_flags_{set|mod|clear} require refactoring that involves moving
vma_start_write() out of these functions and replacing it with
vma_assert_write_locked(), then callers of these functions should
lock the vma themselves using vma_start_write_killable() whenever
possible.

Changes since v4 [1]:
- added Reviewed-by, per Barry Song and Lorenzo Stoakes (wherever the code
stayed the same)
- split patch 2 into 3 parts, per Lorenzo Stoakes
- converted vma_start_write() in mseal_apply(), per Sashiko
- changed vma_start_write_killable() error handling in
set_mempolicy_home_node(), per Lorenzo Stoakes
- added comment why mm->locked_vm is fine even when we exit early,
per Sashiko
- moved vma locking before vrm_calc_charge() in move_vma(), per Sashiko
and Lorenzo Stoakes
- set give_up_on_oom on error in vma_merge_existing_range() to propagate
the error, per Lorenzo Stoakes
- moved validate_mm() out of the error path in expand_upwards(),
per Lorenzo Stoakes
- dropped the patch changing S390 error handling, per Sashiko and
Lorenzo Stoakes
- reworked error handling in clear_refs_write(), per Lorenzo Stoakes
- uninlined process_vma_walk_lock() while changing its return type,
per Lorenzo Stoakes

[1] https://lore.kernel.org/all/20260322054309.898214-1-suren...

Suren Baghdasaryan (6):
  mm/vma: cleanup error handling path in vma_expand()
  mm: use vma_start_write_killable() in mm syscalls
  mm/khugepaged: use vma_start_write_killable() in collapse_huge_page()
  mm/vma: use vma_start_write_killable() in vma operations
  mm: use vma_start_write_killable() in process_vma_walk_lock()
  KVM: PPC: use vma_start_write_killable() in
    kvmppc_memslot_page_merge()

 arch/powerpc/kvm/book3s_hv_uvmem.c |   5 +-
 fs/proc/task_mmu.c                 |  12 +--
 mm/khugepaged.c                    |   5 +-
 mm/madvise.c                       |   4 +-
 mm/memory.c                        |   2 +
 mm/mempolicy.c                     |  12 ++-
 mm/mlock.c                         |  28 ++++--
 mm/mprotect.c                      |   5 +-
 mm/mremap.c                        |   8 +-
 mm/mseal.c                         |   5 +-
 mm/pagewalk.c                      |  22 +++--
 mm/vma.c                           | 146 +++++++++++++++++++++--------
 mm/vma_exec.c                      |   6 +-
 13 files changed, 190 insertions(+), 70 deletions(-)


base-commit: e53c9040ab1b738dd2c83b57558f141902caaf4f
-- 
2.53.0.1018.g2bb0e51243-goog