+ mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: mm/hmm: HMM should have a callback before MM is destroyed
has been added to the -mm tree.  Its filename is
     mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2.patch

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------------------------------------------------------
From: Ralph Campbell <rcampbell@nvidia.com>
Subject: 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/20180316191414.3223-4-jglisse@redhat.com
Signed-off-by: Ralph Campbell <rcampbell@nvidia.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/hmm.h |   10 ++++++++++
 mm/hmm.c            |   18 +++++++++++++++++-
 2 files changed, 27 insertions(+), 1 deletion(-)

diff -puN include/linux/hmm.h~mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2 include/linux/hmm.h
--- a/include/linux/hmm.h~mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2
+++ a/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 -puN mm/hmm.c~mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2 mm/hmm.c
--- a/mm/hmm.c~mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2
+++ a/mm/hmm.c
@@ -160,6 +160,21 @@ static void hmm_invalidate_range(struct
 	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(str
 }
 
 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_mi
 	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);
_

Patches currently in -mm which might be from rcampbell@nvidia.com are

mm-hmm-documentation-editorial-update-to-hmm-documentation.patch
mm-hmm-hmm-should-have-a-callback-before-mm-is-destroyed-v2.patch