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Commit 56c57103 authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

mm/mmu_notifiers: hoist do_mmu_notifier_register down_write to the caller 

This simplifies the code to not have so many one line functions and extra
logic. __mmu_notifier_register() simply becomes the entry point to
register the notifier, and the other one calls it under lock.

Also add a lockdep_assert to check that the callers are holding the lock
as expected.

Link: https://lore.kernel.org/r/20190806231548.25242-2-jgg@ziepe.ca


Suggested-by: default avatarChristoph Hellwig <hch@infradead.org>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarRalph Campbell <rcampbell@nvidia.com>
Tested-by: default avatarRalph Campbell <rcampbell@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 9c240a7b

mm/mmu_notifier.c

+14 −21
Original line number Diff line number Diff line
@@ -236,22 +236,22 @@ void __mmu_notifier_invalidate_range(struct mm_struct *mm, 
}

EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);



static int do_mmu_notifier_register(struct mmu_notifier *mn,

				    struct mm_struct *mm,

				    int take_mmap_sem)

/*

 * Same as mmu_notifier_register but here the caller must hold the

 * mmap_sem in write mode.

 */

int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)

{

	struct mmu_notifier_mm *mmu_notifier_mm;

	int ret;



	lockdep_assert_held_write(&mm->mmap_sem);

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



	ret = -ENOMEM;

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

	if (unlikely(!mmu_notifier_mm))

		goto out;

		return -ENOMEM;



	if (take_mmap_sem)

		down_write(&mm->mmap_sem);

	ret = mm_take_all_locks(mm);

	if (unlikely(ret))

		goto out_clean;
@@ -279,13 +279,11 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, 


	mm_drop_all_locks(mm);

out_clean:

	if (take_mmap_sem)

		up_write(&mm->mmap_sem);

	kfree(mmu_notifier_mm);

out:

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

	return ret;

}

EXPORT_SYMBOL_GPL(__mmu_notifier_register);



/*

 * Must not hold mmap_sem nor any other VM related lock when calling
@@ -302,19 +300,14 @@ static int do_mmu_notifier_register(struct mmu_notifier *mn, 
 */

int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)

{

	return do_mmu_notifier_register(mn, mm, 1);

}

EXPORT_SYMBOL_GPL(mmu_notifier_register);

	int ret;



/*

 * Same as mmu_notifier_register but here the caller must hold the

 * mmap_sem in write mode.

 */

int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)

{

	return do_mmu_notifier_register(mn, mm, 0);

	down_write(&mm->mmap_sem);

	ret = __mmu_notifier_register(mn, mm);

	up_write(&mm->mmap_sem);

	return ret;

}

EXPORT_SYMBOL_GPL(__mmu_notifier_register);

EXPORT_SYMBOL_GPL(mmu_notifier_register);



/* this is called after the last mmu_notifier_unregister() returned */

void __mmu_notifier_mm_destroy(struct mm_struct *mm)