From: Ralph Campbell <rcampbell@nvidia.com>
To: "Christoph Hellwig" <hch@lst.de>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Jason Gunthorpe" <jgg@mellanox.com>,
"Ben Skeggs" <bskeggs@redhat.com>
Cc: Bharata B Rao <bharata@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>,
<nouveau@lists.freedesktop.org>,
<dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 9/9] mm: remove the MIGRATE_PFN_WRITE flag
Date: Mon, 29 Jul 2019 16:42:01 -0700 [thread overview]
Message-ID: <1f0ef337-6ca5-54fa-e627-41a46be73f2b@nvidia.com> (raw)
In-Reply-To: <20190729142843.22320-10-hch@lst.de>
On 7/29/19 7:28 AM, Christoph Hellwig wrote:
> The MIGRATE_PFN_WRITE is only used locally in migrate_vma_collect_pmd,
> where it can be replaced with a simple boolean local variable.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
> ---
> include/linux/migrate.h | 1 -
> mm/migrate.c | 9 +++++----
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/migrate.h b/include/linux/migrate.h
> index 8b46cfdb1a0e..ba74ef5a7702 100644
> --- a/include/linux/migrate.h
> +++ b/include/linux/migrate.h
> @@ -165,7 +165,6 @@ static inline int migrate_misplaced_transhuge_page(struct mm_struct *mm,
> #define MIGRATE_PFN_VALID (1UL << 0)
> #define MIGRATE_PFN_MIGRATE (1UL << 1)
> #define MIGRATE_PFN_LOCKED (1UL << 2)
> -#define MIGRATE_PFN_WRITE (1UL << 3)
> #define MIGRATE_PFN_SHIFT 6
>
> static inline struct page *migrate_pfn_to_page(unsigned long mpfn)
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 74735256e260..724f92dcc31b 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2212,6 +2212,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> unsigned long mpfn, pfn;
> struct page *page;
> swp_entry_t entry;
> + bool writable = false;
> pte_t pte;
>
> pte = *ptep;
> @@ -2240,7 +2241,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> mpfn = migrate_pfn(page_to_pfn(page)) |
> MIGRATE_PFN_MIGRATE;
> if (is_write_device_private_entry(entry))
> - mpfn |= MIGRATE_PFN_WRITE;
> + writable = true;
> } else {
> if (is_zero_pfn(pfn)) {
> mpfn = MIGRATE_PFN_MIGRATE;
> @@ -2250,7 +2251,8 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> }
> page = vm_normal_page(migrate->vma, addr, pte);
> mpfn = migrate_pfn(pfn) | MIGRATE_PFN_MIGRATE;
> - mpfn |= pte_write(pte) ? MIGRATE_PFN_WRITE : 0;
> + if (pte_write(pte))
> + writable = true;
> }
>
> /* FIXME support THP */
> @@ -2284,8 +2286,7 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp,
> ptep_get_and_clear(mm, addr, ptep);
>
> /* Setup special migration page table entry */
> - entry = make_migration_entry(page, mpfn &
> - MIGRATE_PFN_WRITE);
> + entry = make_migration_entry(page, writable);
> swp_pte = swp_entry_to_pte(entry);
> if (pte_soft_dirty(pte))
> swp_pte = pte_swp_mksoft_dirty(swp_pte);
>
MIGRATE_PFN_WRITE may mot being used but that seems like a bug to me.
If a page is migrated to device memory, it could be mapped at the same
time to avoid a device page fault but it would need the flag to know
whether to map it RW or RO. But I suppose that could be inferred from
the vma->vm_flags.
next prev parent reply other threads:[~2019-07-29 23:42 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-29 14:28 turn the hmm migrate_vma upside down Christoph Hellwig
2019-07-29 14:28 ` [PATCH 1/9] mm: turn " Christoph Hellwig
2019-07-29 23:12 ` Ralph Campbell
2019-07-29 23:43 ` Jerome Glisse
2019-07-31 1:46 ` Ralph Campbell
2019-08-01 7:42 ` Christoph Hellwig
2019-07-29 14:28 ` [PATCH 2/9] nouveau: reset dma_nr in nouveau_dmem_migrate_alloc_and_copy Christoph Hellwig
2019-07-29 23:18 ` Ralph Campbell
2019-07-29 14:28 ` [PATCH 3/9] nouveau: factor out device memory address calculation Christoph Hellwig
2019-07-29 23:21 ` Ralph Campbell
2019-07-29 14:28 ` [PATCH 4/9] nouveau: factor out dmem fence completion Christoph Hellwig
2019-07-29 23:23 ` Ralph Campbell
2019-07-29 14:28 ` [PATCH 5/9] nouveau: simplify nouveau_dmem_migrate_to_ram Christoph Hellwig
2019-07-29 23:26 ` Ralph Campbell
2019-07-31 9:57 ` Bharata B Rao
2019-08-01 7:46 ` Christoph Hellwig
2019-07-29 14:28 ` [PATCH 6/9] nouveau: simplify nouveau_dmem_migrate_vma Christoph Hellwig
2019-07-29 23:27 ` Ralph Campbell
2019-07-29 14:28 ` [PATCH 7/9] mm: remove the unused MIGRATE_PFN_ERROR flag Christoph Hellwig
2019-07-29 23:29 ` Ralph Campbell
2019-07-29 14:28 ` [PATCH 8/9] mm: remove the unused MIGRATE_PFN_DEVICE flag Christoph Hellwig
2019-07-29 23:31 ` Ralph Campbell
2019-07-29 14:28 ` [PATCH 9/9] mm: remove the MIGRATE_PFN_WRITE flag Christoph Hellwig
2019-07-29 23:30 ` Jerome Glisse
2019-07-30 5:46 ` Christoph Hellwig
2019-07-30 15:51 ` Jerome Glisse
2019-07-29 23:42 ` Ralph Campbell [this message]
2019-07-29 23:46 ` Jerome Glisse
2019-07-30 12:32 ` turn the hmm migrate_vma upside down Jason Gunthorpe
2019-07-30 13:09 ` Christoph Hellwig
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