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: Jérôme 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: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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38
mm/hmm.c
38
mm/hmm.c
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@ -233,13 +233,24 @@ int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm)
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if (!mm || !mirror || !mirror->ops)
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return -EINVAL;
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again:
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mirror->hmm = hmm_register(mm);
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if (!mirror->hmm)
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return -ENOMEM;
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down_write(&mirror->hmm->mirrors_sem);
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list_add(&mirror->list, &mirror->hmm->mirrors);
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up_write(&mirror->hmm->mirrors_sem);
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if (mirror->hmm->mm == NULL) {
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/*
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* A racing hmm_mirror_unregister() is about to destroy the hmm
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* struct. Try again to allocate a new one.
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*/
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up_write(&mirror->hmm->mirrors_sem);
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mirror->hmm = NULL;
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goto again;
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} else {
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list_add(&mirror->list, &mirror->hmm->mirrors);
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up_write(&mirror->hmm->mirrors_sem);
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}
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return 0;
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}
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@ -254,11 +265,32 @@ EXPORT_SYMBOL(hmm_mirror_register);
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*/
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void hmm_mirror_unregister(struct hmm_mirror *mirror)
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{
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struct hmm *hmm = mirror->hmm;
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bool should_unregister = false;
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struct mm_struct *mm;
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struct hmm *hmm;
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if (mirror->hmm == NULL)
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return;
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hmm = mirror->hmm;
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down_write(&hmm->mirrors_sem);
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list_del_init(&mirror->list);
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should_unregister = list_empty(&hmm->mirrors);
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mirror->hmm = NULL;
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mm = hmm->mm;
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hmm->mm = NULL;
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up_write(&hmm->mirrors_sem);
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if (!should_unregister || mm == NULL)
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return;
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spin_lock(&mm->page_table_lock);
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if (mm->hmm == hmm)
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mm->hmm = NULL;
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spin_unlock(&mm->page_table_lock);
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mmu_notifier_unregister_no_release(&hmm->mmu_notifier, mm);
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kfree(hmm);
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}
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EXPORT_SYMBOL(hmm_mirror_unregister);
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