From: David Hildenbrand <david@redhat.com>
To: Alistair Popple <apopple@nvidia.com>, linux-mm@kvack.org
Cc: 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>,
Jason Gunthorpe <jgg@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
Logan Gunthorpe <logang@deltatee.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Muchun Song <songmuchun@bytedance.com>,
Ralph Campbell <rcampbell@nvidia.com>
Subject: Re: [PATCH v2 2/2] mm/gup.c: Refactor check_and_migrate_movable_pages()
Date: Fri, 5 Aug 2022 10:12:52 +0200 [thread overview]
Message-ID: <ec0d45f9-6dc0-95ab-f0ff-7d6744d24668@redhat.com> (raw)
In-Reply-To: <3f6d04570907ee80f030ffaa85e8f506b3d31fc1.1659680600.git-series.apopple@nvidia.com>
On 05.08.22 08:29, Alistair Popple wrote:
> When pinning pages with FOLL_LONGTERM check_and_migrate_movable_pages()
> is called to migrate pages out of zones which should not contain any
> longterm pinned pages.
>
> When migration succeeds all pages will have been unpinned so pinning
> needs to be retried. Migration can also fail, in which case the pages
> will also have been unpinned but the operation should not be retried. If
> all pages are in the correct zone nothing will be unpinned and no retry
> is required.
>
> The logic in check_and_migrate_movable_pages() tracks unnecessary state
> and the return codes for each case are difficult to follow. Refactor the
> code to clean this up. No behaviour change is intended.
>
> Signed-off-by: Alistair Popple <apopple@nvidia.com>
>
> ---
>
> Changes for v2:
>
> - Split into different functions as suggested by John.
> - Made error handling more conventional as requested by Jason.
>
> Personally I'm not entirely convinced the conventional approach to error
> handling is easier to follow here but have left it in for feedback as I
> might be getting too familiar with the code.
>
> Originally posted as "mm/gup.c: Simplify and fix
> check_and_migrate_movable_pages() return codes"[1].
>
> Changes from that version:
>
> - Restore the original isolation failure behaviour and don't fail the
> pup. Instead retry indefinitely.
> - Unpin all pages on retry or failure rather than just failure.
>
> [1] https://lore.kernel.org/linux-mm/814dee5d3aadd38c3370eaaf438ba7eee9bf9d2b.1659399696.git-series.apopple@nvidia.com/
> ---
> mm/gup.c | 159 ++++++++++++++++++++++++++++++--------------------------
> 1 file changed, 88 insertions(+), 71 deletions(-)
>
> diff --git a/mm/gup.c b/mm/gup.c
> index e26ccc0..60cb30a 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1900,20 +1900,14 @@ struct page *get_dump_page(unsigned long addr)
> #endif /* CONFIG_ELF_CORE */
>
> #ifdef CONFIG_MIGRATION
> -/*
> - * Check whether all pages are pinnable, if so return number of pages. If some
> - * pages are not pinnable, migrate them, and unpin all pages. Return zero if
> - * pages were migrated, or if some pages were not successfully isolated.
> - * Return negative error if migration fails.
> - */
> -static long check_and_migrate_movable_pages(unsigned long nr_pages,
> - struct page **pages)
> +static int collect_unpinnable_pages(struct list_head *movable_page_list,
If we're already renaming stuff, can we make it clearer, that we are
dealing with *longterm* unpinnable pages?
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2022-08-05 8:13 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-05 6:29 [PATCH v2 1/2] mm/gup.c: Don't pass gup_flags to check_and_migrate_movable_pages() Alistair Popple
2022-08-05 6:29 ` [PATCH v2 2/2] mm/gup.c: Refactor check_and_migrate_movable_pages() Alistair Popple
2022-08-05 8:12 ` David Hildenbrand [this message]
2022-08-05 8:15 ` John Hubbard
2022-08-08 1:38 ` Alistair Popple
2022-08-05 7:35 ` [PATCH v2 1/2] mm/gup.c: Don't pass gup_flags to check_and_migrate_movable_pages() John Hubbard
2022-08-05 8:10 ` David Hildenbrand
2022-08-05 12:06 ` Jason Gunthorpe
2022-08-08 1:55 ` Alistair Popple
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