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Subject[PATCH 03/14] mm/hmm: HMM should have a callback before MM is destroyed v2
Date
From: Ralph Campbell <rcampbell@nvidia.com>

The hmm_mirror_register() function 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.

Changed since v1:
- dropped VM_BUG_ON()
- cc stable

Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: stable@vger.kernel.org
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
---
include/linux/hmm.h | 10 ++++++++++
mm/hmm.c | 18 +++++++++++++++++-
2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/include/linux/hmm.h b/include/linux/hmm.h
index ef6044d08cc5..61b0e1c05ee1 100644
--- a/include/linux/hmm.h
+++ b/include/linux/hmm.h
@@ -218,6 +218,16 @@ enum hmm_update_type {
* @update: callback to update range on a device
*/
struct hmm_mirror_ops {
+ /* release() - release hmm_mirror
+ *
+ * @mirror: pointer to struct hmm_mirror
+ *
+ * This is called when the mm_struct is being released.
+ * The callback should make sure no references to the mirror occur
+ * after the callback returns.
+ */
+ void (*release)(struct hmm_mirror *mirror);
+
/* sync_cpu_device_pagetables() - synchronize page tables
*
* @mirror: pointer to struct hmm_mirror
diff --git a/mm/hmm.c b/mm/hmm.c
index 320545b98ff5..6088fa6ed137 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -160,6 +160,21 @@ static void hmm_invalidate_range(struct hmm *hmm,
up_read(&hmm->mirrors_sem);
}

+static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm)
+{
+ struct hmm *hmm = mm->hmm;
+ struct hmm_mirror *mirror;
+ struct hmm_mirror *mirror_next;
+
+ down_write(&hmm->mirrors_sem);
+ list_for_each_entry_safe(mirror, mirror_next, &hmm->mirrors, list) {
+ list_del_init(&mirror->list);
+ if (mirror->ops->release)
+ mirror->ops->release(mirror);
+ }
+ up_write(&hmm->mirrors_sem);
+}
+
static void hmm_invalidate_range_start(struct mmu_notifier *mn,
struct mm_struct *mm,
unsigned long start,
@@ -185,6 +200,7 @@ static void hmm_invalidate_range_end(struct mmu_notifier *mn,
}

static const struct mmu_notifier_ops hmm_mmu_notifier_ops = {
+ .release = hmm_release,
.invalidate_range_start = hmm_invalidate_range_start,
.invalidate_range_end = hmm_invalidate_range_end,
};
@@ -230,7 +246,7 @@ void hmm_mirror_unregister(struct hmm_mirror *mirror)
struct hmm *hmm = mirror->hmm;

down_write(&hmm->mirrors_sem);
- list_del(&mirror->list);
+ list_del_init(&mirror->list);
up_write(&hmm->mirrors_sem);
}
EXPORT_SYMBOL(hmm_mirror_unregister);
--
2.14.3
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