From: Jason Gunthorpe <jgg@nvidia•com>
To: peterx@redhat•com
Cc: James Houghton <jthoughton@google•com>,
David Hildenbrand <david@redhat•com>,
Yang Shi <shy828301@gmail•com>,
Andrew Jones <andrew.jones@linux•dev>,
linux-mm@kvack•org, linux-riscv@lists•infradead.org,
Andrea Arcangeli <aarcange@redhat•com>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel•org>,
Matthew Wilcox <willy@infradead•org>,
Christoph Hellwig <hch@infradead•org>,
linux-arm-kernel@lists•infradead.org,
Axel Rasmussen <axelrasmussen@google•com>,
Rik van Riel <riel@surriel•com>,
John Hubbard <jhubbard@nvidia•com>,
"Kirill A . Shutemov" <kirill@shutemov•name>,
Vlastimil Babka <vbabka@suse•cz>,
Lorenzo Stoakes <lstoakes@gmail•com>,
Muchun Song <muchun.song@linux•dev>,
linux-kernel@vger•kernel.org,
Andrew Morton <akpm@linux-foundation•org>,
linuxppc-dev@lists•ozlabs.org, Mike Rapoport <rppt@kernel•org>,
Mike Kravetz <mike.kravetz@oracle•com>
Subject: Re: [PATCH v3 05/12] mm/gup: Drop folio_fast_pin_allowed() in hugepd processing
Date: Fri, 22 Mar 2024 09:28:42 -0300 [thread overview]
Message-ID: <20240322122842.GH159172@nvidia.com> (raw)
In-Reply-To: <20240321220802.679544-6-peterx@redhat.com>
On Thu, Mar 21, 2024 at 06:07:55PM -0400, peterx@redhat•com wrote:
> From: Peter Xu <peterx@redhat•com>
>
> Hugepd format for GUP is only used in PowerPC with hugetlbfs. There are
> some kernel usage of hugepd (can refer to hugepd_populate_kernel() for
> PPC_8XX), however those pages are not candidates for GUP.
>
> Commit a6e79df92e4a ("mm/gup: disallow FOLL_LONGTERM GUP-fast writing to
> file-backed mappings") added a check to fail gup-fast if there's potential
> risk of violating GUP over writeback file systems. That should never apply
> to hugepd. Considering that hugepd is an old format (and even
> software-only), there's no plan to extend hugepd into other file typed
> memories that is prone to the same issue.
>
> Drop that check, not only because it'll never be true for hugepd per any
> known plan, but also it paves way for reusing the function outside
> fast-gup.
>
> To make sure we'll still remember this issue just in case hugepd will be
> extended to support non-hugetlbfs memories, add a rich comment above
> gup_huge_pd(), explaining the issue with proper references.
>
> Cc: Christoph Hellwig <hch@infradead•org>
> Cc: Lorenzo Stoakes <lstoakes@gmail•com>
> Cc: Michael Ellerman <mpe@ellerman•id.au>
> Cc: linuxppc-dev@lists•ozlabs.org
> Signed-off-by: Peter Xu <peterx@redhat•com>
> ---
> mm/gup.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
Reviewed-by: Jason Gunthorpe <jgg@nvidia•com>
Jason
next prev parent reply other threads:[~2024-03-22 12:29 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-21 22:07 [PATCH v3 00/12] mm/gup: Unify hugetlb, part 2 peterx
2024-03-21 22:07 ` [PATCH v3 01/12] mm/Kconfig: CONFIG_PGTABLE_HAS_HUGE_LEAVES peterx
2024-03-21 22:07 ` [PATCH v3 02/12] mm/hugetlb: Declare hugetlbfs_pagecache_present() non-static peterx
2024-03-21 22:07 ` [PATCH v3 03/12] mm: Make HPAGE_PXD_* macros even if !THP peterx
2024-03-22 17:14 ` SeongJae Park
2024-03-23 0:30 ` Peter Xu
2024-03-23 1:05 ` SeongJae Park
2024-03-21 22:07 ` [PATCH v3 04/12] mm: Introduce vma_pgtable_walk_{begin|end}() peterx
2024-03-22 12:27 ` Jason Gunthorpe
2024-03-21 22:07 ` [PATCH v3 05/12] mm/gup: Drop folio_fast_pin_allowed() in hugepd processing peterx
2024-03-22 12:28 ` Jason Gunthorpe [this message]
2024-03-21 22:07 ` [PATCH v3 06/12] mm/gup: Refactor record_subpages() to find 1st small page peterx
2024-03-21 22:07 ` [PATCH v3 07/12] mm/gup: Handle hugetlb for no_page_table() peterx
2024-03-21 22:07 ` [PATCH v3 08/12] mm/gup: Cache *pudp in follow_pud_mask() peterx
2024-03-21 22:07 ` [PATCH v3 09/12] mm/gup: Handle huge pud for follow_pud_mask() peterx
2024-03-21 22:08 ` [PATCH v3 10/12] mm/gup: Handle huge pmd for follow_pmd_mask() peterx
2024-03-21 22:08 ` [PATCH v3 11/12] mm/gup: Handle hugepd for follow_page() peterx
2024-03-21 22:08 ` [PATCH v3 12/12] mm/gup: Handle hugetlb in the generic follow_page_mask code peterx
2024-03-22 13:30 ` Jason Gunthorpe
2024-03-22 15:55 ` Peter Xu
2024-03-22 16:08 ` Jason Gunthorpe
2024-03-22 20:48 ` Andrew Morton
2024-03-23 0:45 ` Peter Xu
2024-03-23 2:15 ` Peter Xu
2024-03-22 16:10 ` [PATCH v3 00/12] mm/gup: Unify hugetlb, part 2 Jason Gunthorpe
2024-03-25 18:58 ` Peter Xu
2024-03-26 14:02 ` Jason Gunthorpe
2024-04-04 21:48 ` Peter Xu
2024-04-05 18:16 ` Jason Gunthorpe
2024-04-05 21:42 ` Peter Xu
2024-04-09 23:43 ` Jason Gunthorpe
2024-04-10 15:28 ` Peter Xu
2024-04-10 16:30 ` Christophe Leroy
2024-04-10 19:58 ` Peter Xu
2024-04-12 14:27 ` Christophe Leroy
2024-03-25 14:56 ` Christophe Leroy
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