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Subject: Re: [PATCH v3 02/14] mm/mmu_notifier: add an interval tree notifier
To:     Jason Gunthorpe <jgg@mellanox.com>,
        Christoph Hellwig <hch@infradead.org>
CC:     "linux-mm@kvack.org" <linux-mm@kvack.org>,
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On 11/13/19 8:46 AM, Jason Gunthorpe wrote:
> On Wed, Nov 13, 2019 at 05:59:52AM -0800, Christoph Hellwig wrote:
>>> +int mmu_interval_notifier_insert(struct mmu_interval_notifier *mni,
>>> +				      struct mm_struct *mm, unsigned long start,
>>> +				      unsigned long length,
>>> +				      const struct mmu_interval_notifier_ops *ops);
>>> +int mmu_interval_notifier_insert_locked(
>>> +	struct mmu_interval_notifier *mni, struct mm_struct *mm,
>>> +	unsigned long start, unsigned long length,
>>> +	const struct mmu_interval_notifier_ops *ops);
>>
>> Very inconsistent indentation between these two related functions.
> 
> clang-format.. The kernel config is set to prefer a line up under the
> ( if all the arguments will fit within the 80 cols otherwise it does a
> 1 tab continuation indent.
> 
>>> +	/*
>>> +	 * The inv_end incorporates a deferred mechanism like
>>> +	 * rtnl_unlock(). Adds and removes are queued until the final inv_end
>>> +	 * happens then they are progressed. This arrangement for tree updates
>>> +	 * is used to avoid using a blocking lock during
>>> +	 * invalidate_range_start.
>>
>> Nitpick:  That comment can be condensed into one less line:
> 
> The rtnl_unlock can move up a line too. My editor is failing me on
> this.
> 
>>> +	/*
>>> +	 * TODO: Since we already have a spinlock above, this would be faster
>>> +	 * as wake_up_q
>>> +	 */
>>> +	if (need_wake)
>>> +		wake_up_all(&mmn_mm->wq);
>>
>> So why is this important enough for a TODO comment, but not important
>> enough to do right away?
> 
> Lets drop the comment, I'm noto sure wake_up_q is even a function this
> layer should be calling.

Actually, I think you can remove the "need_wake" variable since it is
unconditionally set to "true".

Also, the comment in__mmu_interval_notifier_insert() says
"mni->mr_invalidate_seq" and I think that should be
"mni->invalidate_seq".