From: Jerome Glisse <jglisse@redhat.com>
To: Ralph Campbell <rcampbell@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>,
Jason Gunthorpe <jgg@mellanox.com>,
Ben Skeggs <bskeggs@redhat.com>,
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 19:46:11 -0400 [thread overview]
Message-ID: <20190729234611.GC7171@redhat.com> (raw)
In-Reply-To: <1f0ef337-6ca5-54fa-e627-41a46be73f2b@nvidia.com>
On Mon, Jul 29, 2019 at 04:42:01PM -0700, Ralph Campbell wrote:
>
> 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.
It is a bug that it is not being use right now. I will have to dig my
git repo to see when that got kill. Will look into it once i get back.
The vma->vm_flags is of no use here. A page can be write protected
inside a writable vma for various reasons.
Cheers,
Jérôme
next prev parent reply other threads:[~2019-07-29 23:46 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
2019-07-29 23:46 ` Jerome Glisse [this message]
2019-07-30 12:32 ` turn the hmm migrate_vma upside down Jason Gunthorpe
2019-07-30 13:09 ` Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190729234611.GC7171@redhat.com \
--to=jglisse@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=bharata@linux.ibm.com \
--cc=bskeggs@redhat.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=hch@lst.de \
--cc=jgg@mellanox.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=nouveau@lists.freedesktop.org \
--cc=rcampbell@nvidia.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).