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Commit e0f3c3f7 authored by Gavin Shan's avatar Gavin Shan Committed by Linus Torvalds
Browse files

mm/mmu_notifier: init notifier if necessary 



While registering MMU notifier, new instance of MMU notifier_mm will be
allocated and later free'd if currrent mm_struct's MMU notifier_mm has
been initialized.  That causes some overhead.  The patch tries to
elominate that.

Signed-off-by: default avatarGavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: default avatarWanpeng Li <liwanp@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Sagi Grimberg <sagig@mellanox.co.il>
Cc: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 21a92735

mm/mmu_notifier.c

+11 −11
Original line number Diff line number Diff line
@@ -207,22 +207,23 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, 
	*/

	BUG_ON(!srcu.per_cpu_ref);



	ret = -ENOMEM;

	mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);

	if (unlikely(!mmu_notifier_mm))

		goto out;



	if (take_mmap_sem)

		down_write(&mm->mmap_sem);

	ret = mm_take_all_locks(mm);

	if (unlikely(ret))

		goto out_cleanup;

		goto out;



	if (!mm_has_notifiers(mm)) {

		mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm),

					GFP_KERNEL);

		if (unlikely(!mmu_notifier_mm)) {

			ret = -ENOMEM;

			goto out_of_mem;

		}

		INIT_HLIST_HEAD(&mmu_notifier_mm->list);

		spin_lock_init(&mmu_notifier_mm->lock);



		mm->mmu_notifier_mm = mmu_notifier_mm;

		mmu_notifier_mm = NULL;

	}

	atomic_inc(&mm->mm_count);
@@ -238,13 +239,12 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, 
	hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);

	spin_unlock(&mm->mmu_notifier_mm->lock);



out_of_mem:

	mm_drop_all_locks(mm);

out_cleanup:

out:

	if (take_mmap_sem)

		up_write(&mm->mmap_sem);

	/* kfree() does nothing if mmu_notifier_mm is NULL */

	kfree(mmu_notifier_mm);

out:



	BUG_ON(atomic_read(&mm->mm_users) <= 0);

	return ret;

}