| Message ID | 1565167272-21453-1-git-send-email-kernelfans@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [PATCHv2] mm/migrate: clean up useless code in migrate_vma_collect_pmd() | expand |
On 8/7/19 1:41 AM, Pingfan Liu wrote: > Clean up useless 'pfn' variable. > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > Cc: "Jérôme Glisse" <jglisse@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Mel Gorman <mgorman@techsingularity.net> > Cc: Jan Kara <jack@suse.cz> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Matthew Wilcox <willy@infradead.org> > To: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/migrate.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 8992741..d483a55 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2225,17 +2225,15 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > pte_t pte; > > pte = *ptep; > - pfn = pte_pfn(pte); > > if (pte_none(pte)) { > mpfn = MIGRATE_PFN_MIGRATE; > migrate->cpages++; > - pfn = 0; > goto next; > } > > if (!pte_present(pte)) { > - mpfn = pfn = 0; > + mpfn = 0; > > /* > * Only care about unaddressable device page special > @@ -2252,10 +2250,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > if (is_write_device_private_entry(entry)) > mpfn |= MIGRATE_PFN_WRITE; > } else { > + pfn = pte_pfn(pte); > if (is_zero_pfn(pfn)) { > mpfn = MIGRATE_PFN_MIGRATE; > migrate->cpages++; > - pfn = 0; > goto next; > } > page = vm_normal_page(migrate->vma, addr, pte); > @@ -2265,10 +2263,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > /* FIXME support THP */ > if (!page || !page->mapping || PageTransCompound(page)) { > - mpfn = pfn = 0; > + mpfn = 0; > goto next; > } > - pfn = page_to_pfn(page); > > /* > * By getting a reference on the page we pin it and that blocks > Thanks, I was planning to do this too. Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
On Wed, Aug 07, 2019 at 04:41:12PM +0800, Pingfan Liu wrote: > Clean up useless 'pfn' variable. NAK there is a bug see below: > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > Cc: "Jérôme Glisse" <jglisse@redhat.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Mel Gorman <mgorman@techsingularity.net> > Cc: Jan Kara <jack@suse.cz> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Mike Kravetz <mike.kravetz@oracle.com> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Matthew Wilcox <willy@infradead.org> > To: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/migrate.c | 9 +++------ > 1 file changed, 3 insertions(+), 6 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 8992741..d483a55 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2225,17 +2225,15 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > pte_t pte; > > pte = *ptep; > - pfn = pte_pfn(pte); > > if (pte_none(pte)) { > mpfn = MIGRATE_PFN_MIGRATE; > migrate->cpages++; > - pfn = 0; > goto next; > } > > if (!pte_present(pte)) { > - mpfn = pfn = 0; > + mpfn = 0; > > /* > * Only care about unaddressable device page special > @@ -2252,10 +2250,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > if (is_write_device_private_entry(entry)) > mpfn |= MIGRATE_PFN_WRITE; > } else { > + pfn = pte_pfn(pte); > if (is_zero_pfn(pfn)) { > mpfn = MIGRATE_PFN_MIGRATE; > migrate->cpages++; > - pfn = 0; > goto next; > } > page = vm_normal_page(migrate->vma, addr, pte); > @@ -2265,10 +2263,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > /* FIXME support THP */ > if (!page || !page->mapping || PageTransCompound(page)) { > - mpfn = pfn = 0; > + mpfn = 0; > goto next; > } > - pfn = page_to_pfn(page); You can not remove that one ! Otherwise it will break the device private case.
On 8/15/19 10:19 AM, Jerome Glisse wrote: > On Wed, Aug 07, 2019 at 04:41:12PM +0800, Pingfan Liu wrote: >> Clean up useless 'pfn' variable. > > NAK there is a bug see below: > >> >> Signed-off-by: Pingfan Liu <kernelfans@gmail.com> >> Cc: "Jérôme Glisse" <jglisse@redhat.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Mel Gorman <mgorman@techsingularity.net> >> Cc: Jan Kara <jack@suse.cz> >> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> >> Cc: Michal Hocko <mhocko@suse.com> >> Cc: Mike Kravetz <mike.kravetz@oracle.com> >> Cc: Andrea Arcangeli <aarcange@redhat.com> >> Cc: Matthew Wilcox <willy@infradead.org> >> To: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> --- >> mm/migrate.c | 9 +++------ >> 1 file changed, 3 insertions(+), 6 deletions(-) >> >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 8992741..d483a55 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -2225,17 +2225,15 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, >> pte_t pte; >> >> pte = *ptep; >> - pfn = pte_pfn(pte); >> >> if (pte_none(pte)) { >> mpfn = MIGRATE_PFN_MIGRATE; >> migrate->cpages++; >> - pfn = 0; >> goto next; >> } >> >> if (!pte_present(pte)) { >> - mpfn = pfn = 0; >> + mpfn = 0; >> >> /* >> * Only care about unaddressable device page special >> @@ -2252,10 +2250,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, >> if (is_write_device_private_entry(entry)) >> mpfn |= MIGRATE_PFN_WRITE; >> } else { >> + pfn = pte_pfn(pte); >> if (is_zero_pfn(pfn)) { >> mpfn = MIGRATE_PFN_MIGRATE; >> migrate->cpages++; >> - pfn = 0; >> goto next; >> } >> page = vm_normal_page(migrate->vma, addr, pte); >> @@ -2265,10 +2263,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, >> >> /* FIXME support THP */ >> if (!page || !page->mapping || PageTransCompound(page)) { >> - mpfn = pfn = 0; >> + mpfn = 0; >> goto next; >> } >> - pfn = page_to_pfn(page); > > You can not remove that one ! Otherwise it will break the device > private case. > I don't understand. The only use of "pfn" I see is in the "else" clause above where it is set just before using it.
On Thu, Aug 15, 2019 at 12:23:44PM -0700, Ralph Campbell wrote: > > On 8/15/19 10:19 AM, Jerome Glisse wrote: > > On Wed, Aug 07, 2019 at 04:41:12PM +0800, Pingfan Liu wrote: > > > Clean up useless 'pfn' variable. > > > > NAK there is a bug see below: > > > > > > > > Signed-off-by: Pingfan Liu <kernelfans@gmail.com> > > > Cc: "Jérôme Glisse" <jglisse@redhat.com> > > > Cc: Andrew Morton <akpm@linux-foundation.org> > > > Cc: Mel Gorman <mgorman@techsingularity.net> > > > Cc: Jan Kara <jack@suse.cz> > > > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > > > Cc: Michal Hocko <mhocko@suse.com> > > > Cc: Mike Kravetz <mike.kravetz@oracle.com> > > > Cc: Andrea Arcangeli <aarcange@redhat.com> > > > Cc: Matthew Wilcox <willy@infradead.org> > > > To: linux-mm@kvack.org > > > Cc: linux-kernel@vger.kernel.org > > > --- > > > mm/migrate.c | 9 +++------ > > > 1 file changed, 3 insertions(+), 6 deletions(-) > > > > > > diff --git a/mm/migrate.c b/mm/migrate.c > > > index 8992741..d483a55 100644 > > > --- a/mm/migrate.c > > > +++ b/mm/migrate.c > > > @@ -2225,17 +2225,15 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > > pte_t pte; > > > pte = *ptep; > > > - pfn = pte_pfn(pte); > > > if (pte_none(pte)) { > > > mpfn = MIGRATE_PFN_MIGRATE; > > > migrate->cpages++; > > > - pfn = 0; > > > goto next; > > > } > > > if (!pte_present(pte)) { > > > - mpfn = pfn = 0; > > > + mpfn = 0; > > > /* > > > * Only care about unaddressable device page special > > > @@ -2252,10 +2250,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > > if (is_write_device_private_entry(entry)) > > > mpfn |= MIGRATE_PFN_WRITE; > > > } else { > > > + pfn = pte_pfn(pte); > > > if (is_zero_pfn(pfn)) { > > > mpfn = MIGRATE_PFN_MIGRATE; > > > migrate->cpages++; > > > - pfn = 0; > > > goto next; > > > } > > > page = vm_normal_page(migrate->vma, addr, pte); > > > @@ -2265,10 +2263,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, > > > /* FIXME support THP */ > > > if (!page || !page->mapping || PageTransCompound(page)) { > > > - mpfn = pfn = 0; > > > + mpfn = 0; > > > goto next; > > > } > > > - pfn = page_to_pfn(page); > > > > You can not remove that one ! Otherwise it will break the device > > private case. > > > > I don't understand. The only use of "pfn" I see is in the "else" > clause above where it is set just before using it. Ok i managed to confuse myself with mpfn and probably with old version of the code. Sorry for reading too quickly. Can we move unsigned long pfn; into the else { branch so that there is no more confusion to its scope. Cheers, Jérôme
On Thu, Aug 15, 2019 at 03:40:21PM -0400, Jerome Glisse wrote: > On Thu, Aug 15, 2019 at 12:23:44PM -0700, Ralph Campbell wrote: > [...] > > > > I don't understand. The only use of "pfn" I see is in the "else" > > clause above where it is set just before using it. > > Ok i managed to confuse myself with mpfn and probably with old > version of the code. Sorry for reading too quickly. Can we move > unsigned long pfn; into the else { branch so that there is no > more confusion to its scope. Looks better, I will update v3. Thanks, Pingfan
diff --git a/mm/migrate.c b/mm/migrate.c index 8992741..d483a55 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2225,17 +2225,15 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, pte_t pte; pte = *ptep; - pfn = pte_pfn(pte); if (pte_none(pte)) { mpfn = MIGRATE_PFN_MIGRATE; migrate->cpages++; - pfn = 0; goto next; } if (!pte_present(pte)) { - mpfn = pfn = 0; + mpfn = 0; /* * Only care about unaddressable device page special @@ -2252,10 +2250,10 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, if (is_write_device_private_entry(entry)) mpfn |= MIGRATE_PFN_WRITE; } else { + pfn = pte_pfn(pte); if (is_zero_pfn(pfn)) { mpfn = MIGRATE_PFN_MIGRATE; migrate->cpages++; - pfn = 0; goto next; } page = vm_normal_page(migrate->vma, addr, pte); @@ -2265,10 +2263,9 @@ static int migrate_vma_collect_pmd(pmd_t *pmdp, /* FIXME support THP */ if (!page || !page->mapping || PageTransCompound(page)) { - mpfn = pfn = 0; + mpfn = 0; goto next; } - pfn = page_to_pfn(page); /* * By getting a reference on the page we pin it and that blocks
Clean up useless 'pfn' variable. Signed-off-by: Pingfan Liu <kernelfans@gmail.com> Cc: "Jérôme Glisse" <jglisse@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: Jan Kara <jack@suse.cz> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Matthew Wilcox <willy@infradead.org> To: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/migrate.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-)