| Message ID | 20220901173516.702122-18-surenb@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | per-VMA locks proposal | expand |
Le 01/09/2022 à 19:35, Suren Baghdasaryan a écrit : > Pagefault handlers might need to fire MMU notifications while a new > notifier is being registered. Modify mm_take_all_locks to mark all VMAs > as locked and prevent this race with fault handlers that would hold VMA > locks. > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > --- > mm/mmap.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/mmap.c b/mm/mmap.c > index b31cc97c2803..1edfcd384f5e 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -3538,6 +3538,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) > * hugetlb mapping); > * - all i_mmap_rwsem locks; > * - all anon_vma->rwseml > + * - all vmas marked locked IIRC, the anon_vma may be locked during the page fault handling, and this happens after the VMA is read lock. I think the same applies to i_mmap_rwsem lock. Thus, the VMA should be marked locked first. > * > * We can take all locks within these types randomly because the VM code > * doesn't nest them and we protected from parallel mm_take_all_locks() by > @@ -3579,6 +3580,7 @@ int mm_take_all_locks(struct mm_struct *mm) > if (vma->anon_vma) > list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) > vm_lock_anon_vma(mm, avc->anon_vma); > + vma_mark_locked(vma); > } > > return 0; > @@ -3636,6 +3638,7 @@ void mm_drop_all_locks(struct mm_struct *mm) > mmap_assert_write_locked(mm); > BUG_ON(!mutex_is_locked(&mm_all_locks_mutex)); > > + vma_mark_unlocked_all(mm); > for (vma = mm->mmap; vma; vma = vma->vm_next) { > if (vma->anon_vma) > list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
On Fri, Sep 9, 2022 at 7:20 AM Laurent Dufour <ldufour@linux.ibm.com> wrote: > > Le 01/09/2022 à 19:35, Suren Baghdasaryan a écrit : > > Pagefault handlers might need to fire MMU notifications while a new > > notifier is being registered. Modify mm_take_all_locks to mark all VMAs > > as locked and prevent this race with fault handlers that would hold VMA > > locks. > > > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > > --- > > mm/mmap.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/mmap.c b/mm/mmap.c > > index b31cc97c2803..1edfcd384f5e 100644 > > --- a/mm/mmap.c > > +++ b/mm/mmap.c > > @@ -3538,6 +3538,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) > > * hugetlb mapping); > > * - all i_mmap_rwsem locks; > > * - all anon_vma->rwseml > > + * - all vmas marked locked > > IIRC, the anon_vma may be locked during the page fault handling, and this > happens after the VMA is read lock. I think the same applies to > i_mmap_rwsem lock. > > Thus, the VMA should be marked locked first. I see. I'll double check and move the locking order. Thanks! > > > * > > * We can take all locks within these types randomly because the VM code > > * doesn't nest them and we protected from parallel mm_take_all_locks() by > > @@ -3579,6 +3580,7 @@ int mm_take_all_locks(struct mm_struct *mm) > > if (vma->anon_vma) > > list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) > > vm_lock_anon_vma(mm, avc->anon_vma); > > + vma_mark_locked(vma); > > } > > > > return 0; > > @@ -3636,6 +3638,7 @@ void mm_drop_all_locks(struct mm_struct *mm) > > mmap_assert_write_locked(mm); > > BUG_ON(!mutex_is_locked(&mm_all_locks_mutex)); > > > > + vma_mark_unlocked_all(mm); > > for (vma = mm->mmap; vma; vma = vma->vm_next) { > > if (vma->anon_vma) > > list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) >
diff --git a/mm/mmap.c b/mm/mmap.c index b31cc97c2803..1edfcd384f5e 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -3538,6 +3538,7 @@ static void vm_lock_mapping(struct mm_struct *mm, struct address_space *mapping) * hugetlb mapping); * - all i_mmap_rwsem locks; * - all anon_vma->rwseml + * - all vmas marked locked * * We can take all locks within these types randomly because the VM code * doesn't nest them and we protected from parallel mm_take_all_locks() by @@ -3579,6 +3580,7 @@ int mm_take_all_locks(struct mm_struct *mm) if (vma->anon_vma) list_for_each_entry(avc, &vma->anon_vma_chain, same_vma) vm_lock_anon_vma(mm, avc->anon_vma); + vma_mark_locked(vma); } return 0; @@ -3636,6 +3638,7 @@ void mm_drop_all_locks(struct mm_struct *mm) mmap_assert_write_locked(mm); BUG_ON(!mutex_is_locked(&mm_all_locks_mutex)); + vma_mark_unlocked_all(mm); for (vma = mm->mmap; vma; vma = vma->vm_next) { if (vma->anon_vma) list_for_each_entry(avc, &vma->anon_vma_chain, same_vma)
Pagefault handlers might need to fire MMU notifications while a new notifier is being registered. Modify mm_take_all_locks to mark all VMAs as locked and prevent this race with fault handlers that would hold VMA locks. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- mm/mmap.c | 3 +++ 1 file changed, 3 insertions(+)