Commit c01cbba2 authored by Jérôme Glisse's avatar Jérôme Glisse Committed by Linus Torvalds
Browse files

mm/hmm: unregister mmu_notifier when last HMM client quit 

This code was lost in translation at one point.  This properly call
mmu_notifier_unregister_no_release() once last user is gone.  This fix the
zombie mm_struct as without this patch we do not drop the refcount we have
on it.

Link: http://lkml.kernel.org/r/20180323005527.758-5-jglisse@redhat.com


Signed-off-by: default avatarJérôme Glisse <jglisse@redhat.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e1401513

mm/hmm.c

+35 −3
Original line number Diff line number Diff line
@@ -233,13 +233,24 @@ int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm) 
	if (!mm || !mirror || !mirror->ops)

		return -EINVAL;



again:

	mirror->hmm = hmm_register(mm);

	if (!mirror->hmm)

		return -ENOMEM;



	down_write(&mirror->hmm->mirrors_sem);

	if (mirror->hmm->mm == NULL) {

		/*

		 * A racing hmm_mirror_unregister() is about to destroy the hmm

		 * struct. Try again to allocate a new one.

		 */

		up_write(&mirror->hmm->mirrors_sem);

		mirror->hmm = NULL;

		goto again;

	} else {

		list_add(&mirror->list, &mirror->hmm->mirrors);

		up_write(&mirror->hmm->mirrors_sem);

	}



	return 0;

}
@@ -254,11 +265,32 @@ EXPORT_SYMBOL(hmm_mirror_register); 
 */

void hmm_mirror_unregister(struct hmm_mirror *mirror)

{

	struct hmm *hmm = mirror->hmm;

	bool should_unregister = false;

	struct mm_struct *mm;

	struct hmm *hmm;



	if (mirror->hmm == NULL)

		return;



	hmm = mirror->hmm;

	down_write(&hmm->mirrors_sem);

	list_del_init(&mirror->list);

	should_unregister = list_empty(&hmm->mirrors);

	mirror->hmm = NULL;

	mm = hmm->mm;

	hmm->mm = NULL;

	up_write(&hmm->mirrors_sem);



	if (!should_unregister || mm == NULL)

		return;



	spin_lock(&mm->page_table_lock);

	if (mm->hmm == hmm)

		mm->hmm = NULL;

	spin_unlock(&mm->page_table_lock);



	mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);

	kfree(hmm);

}

EXPORT_SYMBOL(hmm_mirror_unregister);

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