We want to teach lockdep that mmu notifiers can be called from direct reclaim paths, since on many CI systems load might never reach that level (e.g. when just running fuzzer or small functional tests).
Motivated by a discussion with Jason.
I've put the annotation into mmu_notifier_register since only when we have mmu notifiers registered is there any point in teaching lockdep about them. Also, we already have a kmalloc(, GFP_KERNEL), so this is safe.
Cc: Jason Gunthorpe jgg@ziepe.ca Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Andrew Morton akpm@linux-foundation.org Cc: David Rientjes rientjes@google.com Cc: "Jérôme Glisse" jglisse@redhat.com Cc: Michal Hocko mhocko@suse.com Cc: "Christian König" christian.koenig@amd.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Mike Rapoport rppt@linux.vnet.ibm.com Cc: linux-mm@kvack.org Signed-off-by: Daniel Vetter daniel.vetter@intel.com --- mm/mmu_notifier.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c index d12e3079e7a4..538d3bb87f9b 100644 --- a/mm/mmu_notifier.c +++ b/mm/mmu_notifier.c @@ -256,6 +256,13 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn,
BUG_ON(atomic_read(&mm->mm_users) <= 0);
+ if (IS_ENABLED(CONFIG_LOCKDEP)) { + fs_reclaim_acquire(GFP_KERNEL); + lock_map_acquire(&__mmu_notifier_invalidate_range_start_map); + lock_map_release(&__mmu_notifier_invalidate_range_start_map); + fs_reclaim_release(GFP_KERNEL); + } + ret = -ENOMEM; mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL); if (unlikely(!mmu_notifier_mm))