Re: [PATCH v5 0/6] Use killable vma write locking in most places

[Suren Baghdasaryan]

On Thu, Mar 26, 2026 at 2:18 AM Lorenzo Stoakes (Oracle) <ljs@xxxxxxxxxx> wrote:
>
> -cc old email
>
> (Gentle reminder to please send all new stuff to ljs@xxxxxxxxxx - at some
> point I'm going to set a rule to ignore kernel mail sent to the old address
> so, if you need a response you should send to the new :)

Ack, sorry about that and thanks for all the reviews, Lorenzo!

I noticed Sashiko's concerns at [1] and a number of them are false
positives but I see at least one new claim which might be legit. I'll
check if it holds water.

[1] https://sashiko.dev/#/patchset/20260326080836.695207-1-surenb%40google.com

>
>
> On Thu, Mar 26, 2026 at 01:08:30AM -0700, Suren Baghdasaryan wrote:
> > 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-surenb@xxxxxxxxxx/
> >
> > 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
> >