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    SubjectRe: [PATCH 1/4] mm, notifier: Add a lockdep map for invalidate_range_start/end
    On Tue, Aug 20, 2019 at 10:18:59AM +0200, Daniel Vetter wrote:
    > This is a similar idea to the fs_reclaim fake lockdep lock. It's
    > fairly easy to provoke a specific notifier to be run on a specific
    > range: Just prep it, and then munmap() it.
    >
    > A bit harder, but still doable, is to provoke the mmu notifiers for
    > all the various callchains that might lead to them. But both at the
    > same time is really hard to reliable hit, especially when you want to
    > exercise paths like direct reclaim or compaction, where it's not
    > easy to control what exactly will be unmapped.
    >
    > By introducing a lockdep map to tie them all together we allow lockdep
    > to see a lot more dependencies, without having to actually hit them
    > in a single challchain while testing.
    >
    > On Jason's suggestion this is is rolled out for both
    > invalidate_range_start and invalidate_range_end. They both have the
    > same calling context, hence we can share the same lockdep map. Note
    > that the annotation for invalidate_ranage_start is outside of the
    > mm_has_notifiers(), to make sure lockdep is informed about all paths
    > leading to this context irrespective of whether mmu notifiers are
    > present for a given context. We don't do that on the
    > invalidate_range_end side to avoid paying the overhead twice, there
    > the lockdep annotation is pushed down behind the mm_has_notifiers()
    > check.
    >
    > v2: Use lock_map_acquire/release() like fs_reclaim, to avoid confusion
    > with this being a real mutex (Chris Wilson).
    >
    > v3: Rebase on top of Glisse's arg rework.
    >
    > v4: Also annotate invalidate_range_end (Jason Gunthorpe)
    > Also annotate invalidate_range_start_nonblock, I somehow missed that
    > one in the first version.
    >
    > 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>
    > ---
    > include/linux/mmu_notifier.h | 8 ++++++++
    > mm/mmu_notifier.c | 9 +++++++++
    > 2 files changed, 17 insertions(+)

    Reviewed-by: Jason Gunthorpe <jgg@mellanox.com>

    Jason

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