[PATCH v6 0/6] Use killable vma write locking in most places

[Suren Baghdasaryan <surenb@google.com>]

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 v5 [1]:
- Added Reviewed-by for unchanged patches, per Lorenzo Stoakes

Patch#2:
- Fixed locked_vm counter if mlock_vma_pages_range() fails in
mlock_fixup(), per Sashiko
- Avoid VMA re-locking in madvise_update_vma(), mprotect_fixup() and
mseal_apply() when vma_modify_XXX creates a new VMA as it will already be
locked. This prevents the possibility of incomplete operation if signal
happens after a successful vma_modify_XXX modified the vma tree,
per Sashiko
- Removed obsolete comment in madvise_update_vma() and mprotect_fixup()

Patch#4:
- Added clarifying comment for vma_start_write_killable() when locking a
detached VMA
- Override VMA_MERGE_NOMERGE in vma_expand() to prevent callers from
falling back to a new VMA allocation, per Sashiko
- Added a note in the changelog about temporary workaround of using
ENOMEM to propagate the error in vma_merge_existing_range() and
vma_expand()

Patch#5:
- Added fatal_signal_pending() check in do_mbind() to detect
queue_pages_range() failures due to a pendig fatal signal, per Sashiko

[1] https://lore.kernel.org/all/20260326080836.695207-1-surenb@google.com/

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                       |  13 ++-
 mm/memory.c                        |   2 +
 mm/mempolicy.c                     |  21 +++-
 mm/mlock.c                         |  30 ++++--
 mm/mprotect.c                      |  25 +++--
 mm/mremap.c                        |   8 +-
 mm/mseal.c                         |  24 ++++-
 mm/pagewalk.c                      |  22 ++--
 mm/vma.c                           | 162 ++++++++++++++++++++++-------
 mm/vma_exec.c                      |   6 +-
 13 files changed, 251 insertions(+), 84 deletions(-)


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