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Commit e1401513 authored by Ralph Campbell's avatar Ralph Campbell Committed by Linus Torvalds
Browse files

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: default avatarRalph Campbell <rcampbell@nvidia.com>
Signed-off-by: default avatarJérôme Glisse <jglisse@redhat.com>
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Cc: Evgeny Baskakov <ebaskakov@nvidia.com>
Cc: Mark Hairgrove <mhairgrove@nvidia.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b28b08de

include/linux/hmm.h

+10 −0
Original line number Diff line number Diff line
@@ -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

mm/hmm.c

+28 −1
Original line number Diff line number Diff line
@@ -160,6 +160,32 @@ 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_mirror *mirror;

	struct hmm *hmm = mm->hmm;



	down_write(&hmm->mirrors_sem);

	mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror,

					  list);

	while (mirror) {

		list_del_init(&mirror->list);

		if (mirror->ops->release) {

			/*

			 * Drop mirrors_sem so callback can wait on any pending

			 * work that might itself trigger mmu_notifier callback

			 * and thus would deadlock with us.

			 */

			up_write(&hmm->mirrors_sem);

			mirror->ops->release(mirror);

			down_write(&hmm->mirrors_sem);

		}

		mirror = list_first_entry_or_null(&hmm->mirrors,

						  struct hmm_mirror, list);

	}

	up_write(&hmm->mirrors_sem);

}



static void hmm_invalidate_range_start(struct mmu_notifier *mn,

				       struct mm_struct *mm,

				       unsigned long start,
@@ -185,6 +211,7 @@ 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 +257,7 @@ 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);