Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <c6990d62-a456-b7c5-f128-311ee758c161@redhat.com>
Date:   Thu, 1 Sep 2022 19:44:02 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.12.0
Subject: Re: [PATCH v1] mm/gup: adjust stale comment for RCU GUP-fast
Content-Language: en-US
To:     Peter Xu <peterx@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
        Sasha Levin <sasha.levin@oracle.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.vnet.ibm.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Jerome Marchand <jmarchan@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Hugh Dickins <hughd@google.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Yang Shi <shy828301@gmail.com>
References: <20220901072119.37588-1-david@redhat.com>
 <YxDdycTur733hMgt@xz-m1.local>
 <fa0bb4b1-3edd-eb5a-7ad6-dff785d88d8f@redhat.com>
 <YxDghv54uHYMGCfG@xz-m1.local>
 <c9dc3f22-4a72-9b9d-7a74-ad77fe4f3b6e@redhat.com>
 <YxDu51TQTz8lhIPP@xz-m1.local>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat
In-Reply-To: <YxDu51TQTz8lhIPP@xz-m1.local>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 7bit
Precedence: bulk

>>> 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