| Message ID | 20220901173516.702122-10-surenb@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | per-VMA locks proposal | expand |
Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit : > Protect VMA from concurrent page fault handler while performing VMA > protection policy changes. > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > --- > mm/mempolicy.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index b73d3248d976..6be1e5c75556 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -383,8 +383,10 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) > struct vm_area_struct *vma; > > mmap_write_lock(mm); > - for (vma = mm->mmap; vma; vma = vma->vm_next) > + for (vma = mm->mmap; vma; vma = vma->vm_next) { > + vma_mark_locked(vma); > mpol_rebind_policy(vma->vm_policy, new); > + } > mmap_write_unlock(mm); > } > > @@ -632,6 +634,7 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, > struct mmu_gather tlb; > int nr_updated; > > + vma_mark_locked(vma); If I understand that corretly, the VMA itself is not impacted, only the PMDs/PTEs, and they are protected using the page table locks. Am I missing something? > tlb_gather_mmu(&tlb, vma->vm_mm); > > nr_updated = change_protection(&tlb, vma, addr, end, PAGE_NONE, > @@ -765,6 +768,7 @@ static int vma_replace_policy(struct vm_area_struct *vma, > if (IS_ERR(new)) > return PTR_ERR(new); > > + vma_mark_locked(vma); > if (vma->vm_ops && vma->vm_ops->set_policy) { > err = vma->vm_ops->set_policy(vma, new); > if (err)
On Tue, Sep 6, 2022 at 7:48 AM Laurent Dufour <ldufour@linux.ibm.com> wrote: > > Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit : > > Protect VMA from concurrent page fault handler while performing VMA > > protection policy changes. > > > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > > --- > > mm/mempolicy.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > > index b73d3248d976..6be1e5c75556 100644 > > --- a/mm/mempolicy.c > > +++ b/mm/mempolicy.c > > @@ -383,8 +383,10 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) > > struct vm_area_struct *vma; > > > > mmap_write_lock(mm); > > - for (vma = mm->mmap; vma; vma = vma->vm_next) > > + for (vma = mm->mmap; vma; vma = vma->vm_next) { > > + vma_mark_locked(vma); > > mpol_rebind_policy(vma->vm_policy, new); > > + } > > mmap_write_unlock(mm); > > } > > > > @@ -632,6 +634,7 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, > > struct mmu_gather tlb; > > int nr_updated; > > > > + vma_mark_locked(vma); > > If I understand that corretly, the VMA itself is not impacted, only the > PMDs/PTEs, and they are protected using the page table locks. > > Am I missing something? I thought we would not want pages faulting in the VMA for which we are changing the protection. However I think what you are saying is that page table locks would already provide a more granular synchronization with page fault handlers, which makes sense to me. Sounds like we can skip locking the VMA here as well. Nice! > > > tlb_gather_mmu(&tlb, vma->vm_mm); > > > > nr_updated = change_protection(&tlb, vma, addr, end, PAGE_NONE, > > @@ -765,6 +768,7 @@ static int vma_replace_policy(struct vm_area_struct *vma, > > if (IS_ERR(new)) > > return PTR_ERR(new); > > > > + vma_mark_locked(vma); > > if (vma->vm_ops && vma->vm_ops->set_policy) { > > err = vma->vm_ops->set_policy(vma, new); > > if (err) >
diff --git a/mm/mempolicy.c b/mm/mempolicy.c index b73d3248d976..6be1e5c75556 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -383,8 +383,10 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) struct vm_area_struct *vma; mmap_write_lock(mm); - for (vma = mm->mmap; vma; vma = vma->vm_next) + for (vma = mm->mmap; vma; vma = vma->vm_next) { + vma_mark_locked(vma); mpol_rebind_policy(vma->vm_policy, new); + } mmap_write_unlock(mm); } @@ -632,6 +634,7 @@ unsigned long change_prot_numa(struct vm_area_struct *vma, struct mmu_gather tlb; int nr_updated; + vma_mark_locked(vma); tlb_gather_mmu(&tlb, vma->vm_mm); nr_updated = change_protection(&tlb, vma, addr, end, PAGE_NONE, @@ -765,6 +768,7 @@ static int vma_replace_policy(struct vm_area_struct *vma, if (IS_ERR(new)) return PTR_ERR(new); + vma_mark_locked(vma); if (vma->vm_ops && vma->vm_ops->set_policy) { err = vma->vm_ops->set_policy(vma, new); if (err)
Protect VMA from concurrent page fault handler while performing VMA protection policy changes. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- mm/mempolicy.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)