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From:   Jesper Dangaard Brouer <jbrouer@redhat.com>
Subject: Re: [PATCH v3] mm/page_alloc: Further fix __alloc_pages_bulk() return
 value
To:     Mel Gorman <mgorman@techsingularity.net>,
        Chuck Lever <chuck.lever@oracle.com>
Cc:     linux-nfs@vger.kernel.org, linux-mm@kvack.org, brouer@redhat.com
References: <162497449506.16614.7781489905877008435.stgit@klimt.1015granger.net>
 <20210629153349.GG3840@techsingularity.net>
Message-ID: <a61e8076-a505-8021-26a3-3a962fb34773@redhat.com>
Date:   Tue, 29 Jun 2021 18:04:58 +0200
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On 29/06/2021 17.33, Mel Gorman wrote:
> On Tue, Jun 29, 2021 at 09:48:15AM -0400, Chuck Lever wrote:
>> The author of commit b3b64ebd3822 ("mm/page_alloc: do bulk array
>> bounds check after checking populated elements") was possibly
>> confused by the mixture of return values throughout the function.
>>
>> The API contract is clear that the function "Returns the number of
>> pages on the list or array." It does not list zero as a unique
>> return value with a special meaning. Therefore zero is a plausible
>> return value only if @nr_pages is zero or less.
>>
>> Clean up the return logic to make it clear that the returned value
>> is always the total number of pages in the array/list, not the
>> number of pages that were allocated during this call.
>>
>> The only change in behavior with this patch is the value returned
>> if prepare_alloc_pages() fails. To match the API contract, the
>> number of pages currently in the array/list is returned in this
>> case.
>>
>> The call site in __page_pool_alloc_pages_slow() also seems to be
>> confused on this matter. It should be attended to by someone who
>> is familiar with that code.
>>
>> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> Acked-by: Mel Gorman <mgorman@techsingularity.net>
>

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>