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Message-ID: <18ad1a9f-8f00-41c1-9c77-ac3252061852@redhat.com>
Date: Mon, 27 May 2024 09:18:13 +0200
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Subject: Re: [PATCH 1/4] mm/ksm: refactor out try_to_merge_with_zero_page()
To: Chengming Zhou <chengming.zhou@linux.dev>,
 Andrew Morton <akpm@linux-foundation.org>, aarcange@redhat.com,
 hughd@google.com, shr@devkernel.io
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
 zhouchengming@bytedance.com
References: <20240524-b4-ksm-scan-optimize-v1-0-053b31bd7ab4@linux.dev>
 <20240524-b4-ksm-scan-optimize-v1-1-053b31bd7ab4@linux.dev>
 <18259f7c-d57e-4504-91ec-90b7c87aad01@redhat.com>
 <36d4f3a6-c426-4455-b5be-2ab503d380ad@linux.dev>
From: David Hildenbrand <david@redhat.com>
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In-Reply-To: <36d4f3a6-c426-4455-b5be-2ab503d380ad@linux.dev>
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Am 27.05.24 um 06:36 schrieb Chengming Zhou:
> On 2024/5/24 23:12, David Hildenbrand wrote:
>> On 24.05.24 10:56, Chengming Zhou wrote:
>>> In preparation for later changes, refactor out a new function called
>>> try_to_merge_with_zero_page(), which tries to merge with zero page.
>>>
>>> Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev>
>>> ---
>>>    mm/ksm.c | 67 +++++++++++++++++++++++++++++++++++-----------------------------
>>>    1 file changed, 37 insertions(+), 30 deletions(-)
>>>
>>> diff --git a/mm/ksm.c b/mm/ksm.c
>>> index 4dc707d175fa..cbd4ba7ea974 100644
>>> --- a/mm/ksm.c
>>> +++ b/mm/ksm.c
>>> @@ -1531,6 +1531,41 @@ static int try_to_merge_one_page(struct vm_area_struct *vma,
>>>        return err;
>>>    }
>>>    +/* This function returns 0 if the pages were merged, -EFAULT otherwise. */
>>
>> No it doesn't. Check the "err = 0" case.
>>
> 
> Right, how about this: This function returns 0 if the page were merged or the vma
> is out of date, which means we don't need to continue, -EFAULT otherwise.

Maybe slightly adjusted:

This function returns 0 if the pages were merged or if they are no longer 
merging candidates (e.g., VMA stale), -EFAULT otherwise.

-- 
Thanks,

David / dhildenb