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mm/hmm: unregister mmu_notifier when last HMM client quit

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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>
This commit is contained in:
Jérôme Glisse 2018-04-10 16:28:23 -07:00 committed by Linus Torvalds
parent e1401513c6
commit c01cbba2aa
1 changed files with 35 additions and 3 deletions
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38
mm/hmm.c
View file

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