mm/hmm: HMM should have a callback before MM is destroyed
hmm_mirror_register() registers a callback for when the CPU pagetable is modified. Normally, the device driver will call hmm_mirror_unregister() when the process using the device is finished. However, if the process exits uncleanly, the struct_mm can be destroyed with no warning to the device driver. Link: http://lkml.kernel.org/r/20180323005527.758-4-jglisse@redhat.com Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> Signed-off-by: Jérôme Glisse <jglisse@redhat.com> Reviewed-by: John Hubbard <jhubbard@nvidia.com> Cc: Evgeny Baskakov <ebaskakov@nvidia.com> Cc: Mark Hairgrove <mhairgrove@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -218,6 +218,16 @@ enum hmm_update_type {
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* @update: callback to update range on a device
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*/
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struct hmm_mirror_ops {
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/* release() - release hmm_mirror
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*
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* @mirror: pointer to struct hmm_mirror
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*
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* This is called when the mm_struct is being released.
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* The callback should make sure no references to the mirror occur
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* after the callback returns.
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*/
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void (*release)(struct hmm_mirror *mirror);
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/* sync_cpu_device_pagetables() - synchronize page tables
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*
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* @mirror: pointer to struct hmm_mirror
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29
mm/hmm.c
29
mm/hmm.c
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@ -160,6 +160,32 @@ static void hmm_invalidate_range(struct hmm *hmm,
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up_read(&hmm->mirrors_sem);
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}
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static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
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{
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struct hmm_mirror *mirror;
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struct hmm *hmm = mm->hmm;
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down_write(&hmm->mirrors_sem);
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mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,
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list);
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while (mirror) {
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list_del_init(&mirror->list);
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if (mirror->ops->release) {
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/*
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* Drop mirrors_sem so callback can wait on any pending
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* work that might itself trigger mmu_notifier callback
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* and thus would deadlock with us.
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*/
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up_write(&hmm->mirrors_sem);
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mirror->ops->release(mirror);
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down_write(&hmm->mirrors_sem);
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}
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mirror = list_first_entry_or_null(&hmm->mirrors,
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struct hmm_mirror, list);
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}
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up_write(&hmm->mirrors_sem);
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}
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static void hmm_invalidate_range_start(struct mmu_notifier *mn,
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struct mm_struct *mm,
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unsigned long start,
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@ -185,6 +211,7 @@ static void hmm_invalidate_range_end(struct mmu_notifier *mn,
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}
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static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
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.release = hmm_release,
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.invalidate_range_start = hmm_invalidate_range_start,
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.invalidate_range_end = hmm_invalidate_range_end,
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};
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@ -230,7 +257,7 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror)
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struct hmm *hmm = mirror->hmm;
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down_write(&hmm->mirrors_sem);
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list_del(&mirror->list);
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list_del_init(&mirror->list);
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up_write(&hmm->mirrors_sem);
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}
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EXPORT_SYMBOL(hmm_mirror_unregister);
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