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

Suren Baghdasaryan
2026-03-27T20:55:09Z

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