From: Alistair Popple <apopple@nvidia.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>,
linux-mm@kvack.org, akpm@linux-foundation.org,
linux-kernel@vger.kernel.org, "Sierra Guiza,
Alejandro (Alex)" <alex.sierra@amd.com>,
Chaitanya Kulkarni <kch@nvidia.com>,
Dan Williams <dan.j.williams@intel.com>,
Felix Kuehling <Felix.Kuehling@amd.com>,
Logan Gunthorpe <logang@deltatee.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Muchun Song <songmuchun@bytedance.com>,
Ralph Campbell <rcampbell@nvidia.com>,
David Hildenbrand <david@redhat.com>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v4 2/2] mm/gup.c: Refactor check_and_migrate_movable_pages()
Date: Thu, 18 Aug 2022 09:24:28 +1000 [thread overview]
Message-ID: <87k076tpd1.fsf@nvdebian.thelocal> (raw)
In-Reply-To: <Yv1wntznpzSXuTYh@nvidia.com>
Jason Gunthorpe <jgg@nvidia.com> writes:
> On Wed, Aug 17, 2022 at 01:35:12PM -0700, John Hubbard wrote:
>> How's this look to you:
I agree, I think all the refactoring left this written in a weird way. I
was going to suggest this though:
collected = collect_longterm_unpinnable_pages(&movable_page_list,
nr_pages, pages);
if (collected == 0)
return 0;
ret = migrate_longterm_unpinnable_pages(&movable_page_list, nr_pages,
pages);
if (ret)
return ret;
return -EAGAIN;
Which IMHO looks at lot more normal and sane than what I had.
>> collected = collect_longterm_unpinnable_pages(&movable_page_list,
>> nr_pages, pages);
>> if (collected == 0)
>> return 0;
>>
>> ret = migrate_longterm_unpinnable_pages(&movable_page_list, nr_pages,
>> pages);
>>
>> /* If we got here, we have some unpinnable pages... */
>>
>> if (ret == 0) {
>> /*
>> * ...and we successfully migrated those pages. Which means that
>> * the caller should retry the operation now.
>> */
>> ret = -EAGAIN;
>
> return -EAGAIN
>
>> }
>>
>> return ret;
>
> But why return 0 from the helper function in the first place?
To stick with the paradigm of 0 == success. Ie.
migrate_longterm_unpinnable_pages() successfully migrated everything
requested. I don't feel particularly strongly about this though - happy
to return -EAGAIN directly from migrate_longterm_unpinnable_pages() and
just pass that return code up the stack if others think it's clearer.
> Jason
next prev parent reply other threads:[~2022-08-17 23:36 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-12 2:13 [PATCH v4 1/2] mm/gup.c: Don't pass gup_flags to check_and_migrate_movable_pages() Alistair Popple
2022-08-12 2:13 ` [PATCH v4 2/2] mm/gup.c: Refactor check_and_migrate_movable_pages() Alistair Popple
2022-08-12 7:05 ` John Hubbard
2022-08-15 16:15 ` Jason Gunthorpe
2022-08-16 5:29 ` Alistair Popple
2022-08-16 11:29 ` Jason Gunthorpe
2022-08-17 2:01 ` Alistair Popple
2022-08-17 12:09 ` Jason Gunthorpe
2022-08-17 20:35 ` John Hubbard
2022-08-17 22:50 ` Jason Gunthorpe
2022-08-17 23:05 ` John Hubbard
2022-08-17 23:24 ` Alistair Popple [this message]
2022-08-17 23:40 ` Jason Gunthorpe
2022-08-12 12:57 ` [PATCH v4 1/2] mm/gup.c: Don't pass gup_flags to check_and_migrate_movable_pages() Matthew Wilcox
2022-08-12 18:02 ` John Hubbard
2022-08-12 18:11 ` Matthew Wilcox
2022-08-15 5:52 ` Alistair Popple
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