linux-kernel - Re: [PATCH v1] mm/gup: adjust stale comment for RCU GUP-fast

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Message-ID: <c6990d62-a456-b7c5-f128-311ee758c161@redhat.com>
Date:   Thu, 1 Sep 2022 19:44:02 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Sasha Levin <sasha.levin@...cle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Jerome Marchand <jmarchan@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>,
        Yang Shi <shy828301@...il.com>
Subject: Re: [PATCH v1] mm/gup: adjust stale comment for RCU GUP-fast

>>> It can be dropped later if you want to rework the thp collapse side and
>>> finally remove IPI dependency on fast-gup, but so far it seems to me it's
>>> still needed.  Or just drop this patch until that rework happens?
>>
>> The doc as is is obviously stale, why drop this patch?
>>
>> We should see a fix for the THP collapse issue very soon I guess. Most
>> probably this patch will go upstream after that fix.
> 
> No objection to have this patch alone as the removal statement is only
> about "thp split".  But IMHO this patch alone didn't really help a great
> lot, especially if you plan to have more to come that is very relevant to
> this, so it'll be clearer to put them together.  Your call.

I can hold off the resend until the the fix is in place. Then I can add
to the description that we are not aware of remaining IPI dependencies,
and one undocumented case was broken and got fixed without the need for
IPIs.

Thanks!


-- 
Thanks,

David / dhildenb