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

[Lorenzo Stoakes (Oracle)]

-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 :)


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
>