From: Jason Gunthorpe <jgg@nvidia.com>
To: peterx@redhat.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
James Houghton <jthoughton@google.com>,
David Hildenbrand <david@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Yang Shi <shy828301@gmail.com>,
linux-riscv@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
Rik van Riel <riel@surriel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Mike Rapoport <rppt@kernel.org>,
John Hubbard <jhubbard@nvidia.com>,
Vlastimil Babka <vbabka@suse.cz>,
Michael Ellerman <mpe@ellerman.id.au>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Andrew Jones <andrew.jones@linux.dev>,
linuxppc-dev@lists.ozlabs.org,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <muchun.song@linux.dev>,
linux-arm-kernel@lists.infradead.org,
Christoph Hellwig <hch@infradead.org>,
Lorenzo Stoakes <lstoakes@gmail.com>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v2 09/13] mm/gup: Cache *pudp in follow_pud_mask()
Date: Mon, 15 Jan 2024 14:41:02 -0400 [thread overview]
Message-ID: <20240115184102.GU734935@nvidia.com> (raw)
In-Reply-To: <20240103091423.400294-10-peterx@redhat.com>
On Wed, Jan 03, 2024 at 05:14:19PM +0800, peterx@redhat.com wrote:
> From: Peter Xu <peterx@redhat.com>
>
> Introduce "pud_t pud" in the function, so the code won't dereference *pudp
> multiple time. Not only because that looks less straightforward, but also
> because if the dereference really happened, it's not clear whether there
> can be race to see different *pudp values if it's being modified at the
> same time.
>
> Acked-by: James Houghton <jthoughton@google.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> mm/gup.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
I think we have several more case like this, and I ceratinly agree
code should not access a READ_ONCE variable more than once :(
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: peterx@redhat.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
James Houghton <jthoughton@google.com>,
David Hildenbrand <david@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Yang Shi <shy828301@gmail.com>,
linux-riscv@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
Rik van Riel <riel@surriel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Mike Rapoport <rppt@kernel.org>,
John Hubbard <jhubbard@nvidia.com>,
Vlastimil Babka <vbabka@suse.cz>,
Michael Ellerman <mpe@ellerman.id.au>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Andrew Jones <andrew.jones@linux.dev>,
linuxppc-dev@lists.ozlabs.org,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <muchun.song@linux.dev>,
linux-arm-kernel@lists.infradead.org,
Christoph Hellwig <hch@infradead.org>,
Lorenzo Stoakes <lstoakes@gmail.com>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v2 09/13] mm/gup: Cache *pudp in follow_pud_mask()
Date: Mon, 15 Jan 2024 14:41:02 -0400 [thread overview]
Message-ID: <20240115184102.GU734935@nvidia.com> (raw)
In-Reply-To: <20240103091423.400294-10-peterx@redhat.com>
On Wed, Jan 03, 2024 at 05:14:19PM +0800, peterx@redhat.com wrote:
> From: Peter Xu <peterx@redhat.com>
>
> Introduce "pud_t pud" in the function, so the code won't dereference *pudp
> multiple time. Not only because that looks less straightforward, but also
> because if the dereference really happened, it's not clear whether there
> can be race to see different *pudp values if it's being modified at the
> same time.
>
> Acked-by: James Houghton <jthoughton@google.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> mm/gup.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
I think we have several more case like this, and I ceratinly agree
code should not access a READ_ONCE variable more than once :(
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
WARNING: multiple messages have this Message-ID (diff)
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, Matthew Wilcox <willy@infradead.org>,
linux-riscv@lists.infradead.org,
Andrea Arcangeli <aarcange@redhat.com>,
Christoph Hellwig <hch@infradead.org>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
Vlastimil Babka <vbabka@suse.cz>,
Axel Rasmussen <axelrasmussen@google.com>,
Rik van Riel <riel@surriel.com>,
John Hubbard <jhubbard@nvidia.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
linux-arm-kernel@lists.infradead.org,
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 v2 09/13] mm/gup: Cache *pudp in follow_pud_mask()
Date: Mon, 15 Jan 2024 14:41:02 -0400 [thread overview]
Message-ID: <20240115184102.GU734935@nvidia.com> (raw)
In-Reply-To: <20240103091423.400294-10-peterx@redhat.com>
On Wed, Jan 03, 2024 at 05:14:19PM +0800, peterx@redhat.com wrote:
> From: Peter Xu <peterx@redhat.com>
>
> Introduce "pud_t pud" in the function, so the code won't dereference *pudp
> multiple time. Not only because that looks less straightforward, but also
> because if the dereference really happened, it's not clear whether there
> can be race to see different *pudp values if it's being modified at the
> same time.
>
> Acked-by: James Houghton <jthoughton@google.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> mm/gup.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
I think we have several more case like this, and I ceratinly agree
code should not access a READ_ONCE variable more than once :(
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: peterx@redhat.com
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
James Houghton <jthoughton@google.com>,
David Hildenbrand <david@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Yang Shi <shy828301@gmail.com>,
linux-riscv@lists.infradead.org,
Andrew Morton <akpm@linux-foundation.org>,
"Aneesh Kumar K . V" <aneesh.kumar@kernel.org>,
Rik van Riel <riel@surriel.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Mike Rapoport <rppt@kernel.org>,
John Hubbard <jhubbard@nvidia.com>,
Vlastimil Babka <vbabka@suse.cz>,
Michael Ellerman <mpe@ellerman.id.au>,
Christophe Leroy <christophe.leroy@csgroup.eu>,
Andrew Jones <andrew.jones@linux.dev>,
linuxppc-dev@lists.ozlabs.org,
Mike Kravetz <mike.kravetz@oracle.com>,
Muchun Song <muchun.song@linux.dev>,
linux-arm-kernel@lists.infradead.org,
Christoph Hellwig <hch@infradead.org>,
Lorenzo Stoakes <lstoakes@gmail.com>,
Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH v2 09/13] mm/gup: Cache *pudp in follow_pud_mask()
Date: Mon, 15 Jan 2024 14:41:02 -0400 [thread overview]
Message-ID: <20240115184102.GU734935@nvidia.com> (raw)
In-Reply-To: <20240103091423.400294-10-peterx@redhat.com>
On Wed, Jan 03, 2024 at 05:14:19PM +0800, peterx@redhat.com wrote:
> From: Peter Xu <peterx@redhat.com>
>
> Introduce "pud_t pud" in the function, so the code won't dereference *pudp
> multiple time. Not only because that looks less straightforward, but also
> because if the dereference really happened, it's not clear whether there
> can be race to see different *pudp values if it's being modified at the
> same time.
>
> Acked-by: James Houghton <jthoughton@google.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> mm/gup.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
I think we have several more case like this, and I ceratinly agree
code should not access a READ_ONCE variable more than once :(
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Jason
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2024-01-15 18:41 UTC|newest]
Thread overview: 143+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-03 9:14 [PATCH v2 00/13] mm/gup: Unify hugetlb, part 2 peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` [PATCH v2 01/13] mm/Kconfig: CONFIG_PGTABLE_HAS_HUGE_LEAVES peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 17:37 ` Jason Gunthorpe
2024-01-15 17:37 ` Jason Gunthorpe
2024-01-15 17:37 ` Jason Gunthorpe
2024-01-15 17:37 ` Jason Gunthorpe
2024-01-22 8:25 ` Peter Xu
2024-01-22 8:25 ` Peter Xu
2024-01-22 8:25 ` Peter Xu
2024-01-22 8:25 ` Peter Xu
2024-01-03 9:14 ` [PATCH v2 02/13] mm/hugetlb: Declare hugetlbfs_pagecache_present() non-static peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` [PATCH v2 03/13] mm: Provide generic pmd_thp_or_huge() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 17:55 ` Jason Gunthorpe
2024-01-15 17:55 ` Jason Gunthorpe
2024-01-15 17:55 ` Jason Gunthorpe
2024-01-15 17:55 ` Jason Gunthorpe
2024-02-21 9:37 ` Peter Xu
2024-02-21 9:37 ` Peter Xu
2024-02-21 9:37 ` Peter Xu
2024-02-21 9:37 ` Peter Xu
2024-02-21 12:57 ` Jason Gunthorpe
2024-02-21 12:57 ` Jason Gunthorpe
2024-02-21 12:57 ` Jason Gunthorpe
2024-02-21 12:57 ` Jason Gunthorpe
2024-02-22 8:04 ` Peter Xu
2024-02-22 8:04 ` Peter Xu
2024-02-22 8:04 ` Peter Xu
2024-02-22 8:04 ` Peter Xu
2024-01-03 9:14 ` [PATCH v2 04/13] mm: Make HPAGE_PXD_* macros even if !THP peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 17:59 ` Jason Gunthorpe
2024-01-15 17:59 ` Jason Gunthorpe
2024-01-15 17:59 ` Jason Gunthorpe
2024-01-15 17:59 ` Jason Gunthorpe
2024-01-03 9:14 ` [PATCH v2 05/13] mm: Introduce vma_pgtable_walk_{begin|end}() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` [PATCH v2 06/13] mm/gup: Drop folio_fast_pin_allowed() in hugepd processing peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 18:37 ` Jason Gunthorpe
2024-01-15 18:37 ` Jason Gunthorpe
2024-01-15 18:37 ` Jason Gunthorpe
2024-01-15 18:37 ` Jason Gunthorpe
2024-01-16 6:30 ` Christophe Leroy
2024-01-16 6:30 ` Christophe Leroy
2024-01-16 6:30 ` Christophe Leroy
2024-01-16 6:30 ` Christophe Leroy
2024-01-16 12:31 ` Jason Gunthorpe
2024-01-16 12:31 ` Jason Gunthorpe
2024-01-16 12:31 ` Jason Gunthorpe
2024-01-16 12:31 ` Jason Gunthorpe
2024-01-16 18:32 ` Christophe Leroy
2024-01-16 18:32 ` Christophe Leroy
2024-01-16 18:32 ` Christophe Leroy
2024-01-17 13:22 ` Jason Gunthorpe
2024-01-17 13:22 ` Jason Gunthorpe
2024-01-17 13:22 ` Jason Gunthorpe
2024-01-17 13:22 ` Jason Gunthorpe
2024-01-18 15:15 ` Ryan Roberts
2024-01-18 15:15 ` Ryan Roberts
2024-01-18 15:15 ` Ryan Roberts
2024-01-18 15:15 ` Ryan Roberts
2024-02-21 11:55 ` Peter Xu
2024-02-21 11:55 ` Peter Xu
2024-02-21 11:55 ` Peter Xu
2024-02-21 11:55 ` Peter Xu
2024-01-03 9:14 ` [PATCH v2 07/13] mm/gup: Refactor record_subpages() to find 1st small page peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 18:38 ` Jason Gunthorpe
2024-01-15 18:38 ` Jason Gunthorpe
2024-01-15 18:38 ` Jason Gunthorpe
2024-01-15 18:38 ` Jason Gunthorpe
2024-01-03 9:14 ` [PATCH v2 08/13] mm/gup: Handle hugetlb for no_page_table() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 18:39 ` Jason Gunthorpe
2024-01-15 18:39 ` Jason Gunthorpe
2024-01-15 18:39 ` Jason Gunthorpe
2024-01-15 18:39 ` Jason Gunthorpe
2024-01-03 9:14 ` [PATCH v2 09/13] mm/gup: Cache *pudp in follow_pud_mask() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 18:41 ` Jason Gunthorpe [this message]
2024-01-15 18:41 ` Jason Gunthorpe
2024-01-15 18:41 ` Jason Gunthorpe
2024-01-15 18:41 ` Jason Gunthorpe
2024-01-03 9:14 ` [PATCH v2 10/13] mm/gup: Handle huge pud for follow_pud_mask() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 18:49 ` Jason Gunthorpe
2024-01-15 18:49 ` Jason Gunthorpe
2024-01-15 18:49 ` Jason Gunthorpe
2024-01-15 18:49 ` Jason Gunthorpe
2024-02-21 11:49 ` Peter Xu
2024-02-21 11:49 ` Peter Xu
2024-02-21 11:49 ` Peter Xu
2024-02-21 11:49 ` Peter Xu
2024-01-03 9:14 ` [PATCH v2 11/13] mm/gup: Handle huge pmd for follow_pmd_mask() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-15 18:51 ` Jason Gunthorpe
2024-01-15 18:51 ` Jason Gunthorpe
2024-01-15 18:51 ` Jason Gunthorpe
2024-01-15 18:51 ` Jason Gunthorpe
2024-01-03 9:14 ` [PATCH v2 12/13] mm/gup: Handle hugepd for follow_page() peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` [PATCH v2 13/13] mm/gup: Handle hugetlb in the generic follow_page_mask code peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 9:14 ` peterx
2024-01-03 11:14 ` [PATCH v2 00/13] mm/gup: Unify hugetlb, part 2 Christophe Leroy
2024-01-03 11:14 ` Christophe Leroy
2024-01-03 11:14 ` Christophe Leroy
2024-01-03 11:14 ` Christophe Leroy
2024-01-08 7:27 ` Peter Xu
2024-01-08 7:27 ` Peter Xu
2024-01-08 7:27 ` Peter Xu
2024-01-08 7:27 ` Peter Xu
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