| Message ID | 20190917153129.12905-1-aneesh.kumar@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v6] mm/pgmap: Use correct alignment when looking at first pfn from a region | expand |
On 9/17/19 8:31 AM, Aneesh Kumar K.V wrote: > vmem_altmap_offset() adjust the section aligned base_pfn offset. > So we need to make sure we account for the same when computing base_pfn. > > ie, for altmap_valid case, our pfn_first should be: > > pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > --- > * changes from v5 > * update commit subject and use linux-mm for merge > > mm/memremap.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/mm/memremap.c b/mm/memremap.c > index ed70c4e8e52a..233908d7df75 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -54,8 +54,16 @@ static void pgmap_array_delete(struct resource *res) > > static unsigned long pfn_first(struct dev_pagemap *pgmap) > { > - return PHYS_PFN(pgmap->res.start) + > - vmem_altmap_offset(pgmap_altmap(pgmap)); > + const struct resource *res = &pgmap->res; > + struct vmem_altmap *altmap = pgmap_altmap(pgmap); > + unsigned long pfn; > + > + if (altmap) { > + pfn = altmap->base_pfn + vmem_altmap_offset(altmap); > + } else A nit: you don't need the '{}'s > + pfn = PHYS_PFN(res->start); > + > + return pfn; > } > > static unsigned long pfn_end(struct dev_pagemap *pgmap) >
On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > vmem_altmap_offset() adjust the section aligned base_pfn offset. > So we need to make sure we account for the same when computing base_pfn. > > ie, for altmap_valid case, our pfn_first should be: > > pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); What are the user-visible runtime effects of this change?
Andrew Morton <akpm@linux-foundation.org> writes: > On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > >> vmem_altmap_offset() adjust the section aligned base_pfn offset. >> So we need to make sure we account for the same when computing base_pfn. >> >> ie, for altmap_valid case, our pfn_first should be: >> >> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > > What are the user-visible runtime effects of this change? This was found by code inspection. If the pmem region is not correctly section aligned we can skip pfns while iterating device pfn using for_each_device_pfn(pfn, pgmap) I still would want Dan to ack the change though. -aneesh
On Wed, 25 Sep 2019 09:21:02 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > Andrew Morton <akpm@linux-foundation.org> writes: > > > On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > > > >> vmem_altmap_offset() adjust the section aligned base_pfn offset. > >> So we need to make sure we account for the same when computing base_pfn. > >> > >> ie, for altmap_valid case, our pfn_first should be: > >> > >> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > > > > What are the user-visible runtime effects of this change? > > This was found by code inspection. If the pmem region is not correctly > section aligned we can skip pfns while iterating device pfn using > for_each_device_pfn(pfn, pgmap) > > > I still would want Dan to ack the change though. > Dan? From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> Subject: mm/pgmap: use correct alignment when looking at first pfn from a region vmem_altmap_offset() adjusts the section aligned base_pfn offset. So we need to make sure we account for the same when computing base_pfn. ie, for altmap_valid case, our pfn_first should be: pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); This was found by code inspection. If the pmem region is not correctly section aligned we can skip pfns while iterating device pfn using for_each_device_pfn(pfn, pgmap) [akpm@linux-foundation.org: coding style fixes] Link: http://lkml.kernel.org/r/20190917153129.12905-1-aneesh.kumar@linux.ibm.com Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Ralph Campbell <rcampbell@nvidia.com> Cc: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- mm/memremap.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) --- a/mm/memremap.c~mm-pgmap-use-correct-alignment-when-looking-at-first-pfn-from-a-region +++ a/mm/memremap.c @@ -55,8 +55,16 @@ static void pgmap_array_delete(struct re static unsigned long pfn_first(struct dev_pagemap *pgmap) { - return PHYS_PFN(pgmap->res.start) + - vmem_altmap_offset(pgmap_altmap(pgmap)); + const struct resource *res = &pgmap->res; + struct vmem_altmap *altmap = pgmap_altmap(pgmap); + unsigned long pfn; + + if (altmap) + pfn = altmap->base_pfn + vmem_altmap_offset(altmap); + else + pfn = PHYS_PFN(res->start); + + return pfn; } static unsigned long pfn_end(struct dev_pagemap *pgmap)
On Sat, Nov 30, 2019 at 3:13 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Wed, 25 Sep 2019 09:21:02 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > > > Andrew Morton <akpm@linux-foundation.org> writes: > > > > > On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > > > > > >> vmem_altmap_offset() adjust the section aligned base_pfn offset. > > >> So we need to make sure we account for the same when computing base_pfn. > > >> > > >> ie, for altmap_valid case, our pfn_first should be: > > >> > > >> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > > > > > > What are the user-visible runtime effects of this change? > > > > This was found by code inspection. If the pmem region is not correctly > > section aligned we can skip pfns while iterating device pfn using > > for_each_device_pfn(pfn, pgmap) > > > > > > I still would want Dan to ack the change though. > > > > Dan? > > > From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> > Subject: mm/pgmap: use correct alignment when looking at first pfn from a region > > vmem_altmap_offset() adjusts the section aligned base_pfn offset. So we > need to make sure we account for the same when computing base_pfn. > > ie, for altmap_valid case, our pfn_first should be: > > pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > > This was found by code inspection. If the pmem region is not correctly > section aligned we can skip pfns while iterating device pfn using > > for_each_device_pfn(pfn, pgmap) > > [akpm@linux-foundation.org: coding style fixes] > Link: http://lkml.kernel.org/r/20190917153129.12905-1-aneesh.kumar@linux.ibm.com > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > Cc: Ralph Campbell <rcampbell@nvidia.com> > Cc: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > --- > > mm/memremap.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > --- a/mm/memremap.c~mm-pgmap-use-correct-alignment-when-looking-at-first-pfn-from-a-region > +++ a/mm/memremap.c > @@ -55,8 +55,16 @@ static void pgmap_array_delete(struct re > > static unsigned long pfn_first(struct dev_pagemap *pgmap) > { > - return PHYS_PFN(pgmap->res.start) + > - vmem_altmap_offset(pgmap_altmap(pgmap)); > + const struct resource *res = &pgmap->res; > + struct vmem_altmap *altmap = pgmap_altmap(pgmap); > + unsigned long pfn; > + > + if (altmap) > + pfn = altmap->base_pfn + vmem_altmap_offset(altmap); > + else > + pfn = PHYS_PFN(res->start); This would only be a problem if res->start is not subsection aligned. Is that bug triggering in your case, or is this just inspection. Now that the subsections can be assumed as the minimum mapping granularity I'd rather see a cleanup I'd rather cleanup the implementation to eliminate altmap->base_pfn or at least assert that PHYS_PFN(res->start) and altmap->base_pfn are always identical. Otherwise ->base_pfn is supposed to be just a convenient way to recall the bounds of the memory hotplug operation deeper in the vmemmap setup.
On 12/3/19 6:20 AM, Dan Williams wrote: > On Sat, Nov 30, 2019 at 3:13 PM Andrew Morton <akpm@linux-foundation.org> wrote: >> >> On Wed, 25 Sep 2019 09:21:02 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: >> >>> Andrew Morton <akpm@linux-foundation.org> writes: >>> >>>> On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: >>>> >>>>> vmem_altmap_offset() adjust the section aligned base_pfn offset. >>>>> So we need to make sure we account for the same when computing base_pfn. >>>>> >>>>> ie, for altmap_valid case, our pfn_first should be: >>>>> >>>>> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); >>>> >>>> What are the user-visible runtime effects of this change? >>> >>> This was found by code inspection. If the pmem region is not correctly >>> section aligned we can skip pfns while iterating device pfn using >>> for_each_device_pfn(pfn, pgmap) >>> >>> >>> I still would want Dan to ack the change though. >>> >> >> Dan? >> >> >> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> >> Subject: mm/pgmap: use correct alignment when looking at first pfn from a region >> >> vmem_altmap_offset() adjusts the section aligned base_pfn offset. So we >> need to make sure we account for the same when computing base_pfn. >> >> ie, for altmap_valid case, our pfn_first should be: >> >> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); >> >> This was found by code inspection. If the pmem region is not correctly >> section aligned we can skip pfns while iterating device pfn using >> >> for_each_device_pfn(pfn, pgmap) >> >> [akpm@linux-foundation.org: coding style fixes] >> Link: http://lkml.kernel.org/r/20190917153129.12905-1-aneesh.kumar@linux.ibm.com >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >> Cc: Ralph Campbell <rcampbell@nvidia.com> >> Cc: Dan Williams <dan.j.williams@intel.com> >> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> >> --- >> >> mm/memremap.c | 12 ++++++++++-- >> 1 file changed, 10 insertions(+), 2 deletions(-) >> >> --- a/mm/memremap.c~mm-pgmap-use-correct-alignment-when-looking-at-first-pfn-from-a-region >> +++ a/mm/memremap.c >> @@ -55,8 +55,16 @@ static void pgmap_array_delete(struct re >> >> static unsigned long pfn_first(struct dev_pagemap *pgmap) >> { >> - return PHYS_PFN(pgmap->res.start) + >> - vmem_altmap_offset(pgmap_altmap(pgmap)); >> + const struct resource *res = &pgmap->res; >> + struct vmem_altmap *altmap = pgmap_altmap(pgmap); >> + unsigned long pfn; >> + >> + if (altmap) >> + pfn = altmap->base_pfn + vmem_altmap_offset(altmap); >> + else >> + pfn = PHYS_PFN(res->start); > > This would only be a problem if res->start is not subsection aligned. Kernel is not enforcing this right? ie, If i create multiple namespace as below ndctl create-namespace -s 16908288 --align 64K I can get base_pfn different from res->start PHYS_PFN Yes that results in other error as below with the current upstream. [ 17.491097] memory add fail, invalid altmap > Is that bug triggering in your case, or is this just inspection. Now > that the subsections can be assumed as the minimum mapping granularity > I'd rather see a cleanup I'd rather cleanup the implementation to > eliminate altmap->base_pfn or at least assert that > PHYS_PFN(res->start) and altmap->base_pfn are always identical. > > Otherwise ->base_pfn is supposed to be just a convenient way to recall > the bounds of the memory hotplug operation deeper in the vmemmap > setup. > Is the right fix to ensure that we always make sure res->start is subsection aligned ? If so we may need the patch series https://patchwork.kernel.org/project/linux-nvdimm/list/?series=209373 And enforce that to be multiple of subsection size? -aneesh
On Tue, 3 Dec 2019 15:42:28 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > On 12/3/19 6:20 AM, Dan Williams wrote: > > On Sat, Nov 30, 2019 at 3:13 PM Andrew Morton <akpm@linux-foundation.org> wrote: > >> > >> On Wed, 25 Sep 2019 09:21:02 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > >> > >>> Andrew Morton <akpm@linux-foundation.org> writes: > >>> > >>>> On Tue, 17 Sep 2019 21:01:29 +0530 "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> wrote: > >>>> > >>>>> vmem_altmap_offset() adjust the section aligned base_pfn offset. > >>>>> So we need to make sure we account for the same when computing base_pfn. > >>>>> > >>>>> ie, for altmap_valid case, our pfn_first should be: > >>>>> > >>>>> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > >>>> > >>>> What are the user-visible runtime effects of this change? > >>> > >>> This was found by code inspection. If the pmem region is not correctly > >>> section aligned we can skip pfns while iterating device pfn using > >>> for_each_device_pfn(pfn, pgmap) > >>> > >>> > >>> I still would want Dan to ack the change though. > >>> > >> > >> Dan? > >> > >> > >> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com> > >> Subject: mm/pgmap: use correct alignment when looking at first pfn from a region > >> > >> vmem_altmap_offset() adjusts the section aligned base_pfn offset. So we > >> need to make sure we account for the same when computing base_pfn. > >> > >> ie, for altmap_valid case, our pfn_first should be: > >> > >> pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); > >> > >> This was found by code inspection. If the pmem region is not correctly > >> section aligned we can skip pfns while iterating device pfn using > >> > >> for_each_device_pfn(pfn, pgmap) > >> > >> [akpm@linux-foundation.org: coding style fixes] > >> Link: http://lkml.kernel.org/r/20190917153129.12905-1-aneesh.kumar@linux.ibm.com > >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > >> Cc: Ralph Campbell <rcampbell@nvidia.com> > >> Cc: Dan Williams <dan.j.williams@intel.com> > >> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> > >> --- > >> > >> mm/memremap.c | 12 ++++++++++-- > >> 1 file changed, 10 insertions(+), 2 deletions(-) > >> > >> --- a/mm/memremap.c~mm-pgmap-use-correct-alignment-when-looking-at-first-pfn-from-a-region > >> +++ a/mm/memremap.c > >> @@ -55,8 +55,16 @@ static void pgmap_array_delete(struct re > >> > >> static unsigned long pfn_first(struct dev_pagemap *pgmap) > >> { > >> - return PHYS_PFN(pgmap->res.start) + > >> - vmem_altmap_offset(pgmap_altmap(pgmap)); > >> + const struct resource *res = &pgmap->res; > >> + struct vmem_altmap *altmap = pgmap_altmap(pgmap); > >> + unsigned long pfn; > >> + > >> + if (altmap) > >> + pfn = altmap->base_pfn + vmem_altmap_offset(altmap); > >> + else > >> + pfn = PHYS_PFN(res->start); > > > > This would only be a problem if res->start is not subsection aligned. > > Kernel is not enforcing this right? ie, If i create multiple namespace > as below > > ndctl create-namespace -s 16908288 --align 64K > > I can get base_pfn different from res->start PHYS_PFN > > Yes that results in other error as below with the current upstream. > > [ 17.491097] memory add fail, invalid altmap > > > > > Is that bug triggering in your case, or is this just inspection. Now > > that the subsections can be assumed as the minimum mapping granularity > > I'd rather see a cleanup I'd rather cleanup the implementation to > > eliminate altmap->base_pfn or at least assert that > > PHYS_PFN(res->start) and altmap->base_pfn are always identical. > > > > Otherwise ->base_pfn is supposed to be just a convenient way to recall > > the bounds of the memory hotplug operation deeper in the vmemmap > > setup. > > > > Is the right fix to ensure that we always make sure res->start is > subsection aligned ? If so we may need the patch series > https://patchwork.kernel.org/project/linux-nvdimm/list/?series=209373 > > And enforce that to be multiple of subsection size? No response here? This patch has been floating around for rather a long time. I think I'll drop it for now - please resend if still interested?
diff --git a/mm/memremap.c b/mm/memremap.c index ed70c4e8e52a..233908d7df75 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -54,8 +54,16 @@ static void pgmap_array_delete(struct resource *res) static unsigned long pfn_first(struct dev_pagemap *pgmap) { - return PHYS_PFN(pgmap->res.start) + - vmem_altmap_offset(pgmap_altmap(pgmap)); + const struct resource *res = &pgmap->res; + struct vmem_altmap *altmap = pgmap_altmap(pgmap); + unsigned long pfn; + + if (altmap) { + pfn = altmap->base_pfn + vmem_altmap_offset(altmap); + } else + pfn = PHYS_PFN(res->start); + + return pfn; } static unsigned long pfn_end(struct dev_pagemap *pgmap)
vmem_altmap_offset() adjust the section aligned base_pfn offset. So we need to make sure we account for the same when computing base_pfn. ie, for altmap_valid case, our pfn_first should be: pfn_first = altmap->base_pfn + vmem_altmap_offset(altmap); Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> --- * changes from v5 * update commit subject and use linux-mm for merge mm/memremap.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)