| Message ID | 20200206231629.14151-2-richardw.yang@linux.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Fixes "mm/sparsemem: support sub-section hotplug" | expand |
On Thu, Feb 6, 2020 at 3:17 PM Wei Yang <richardw.yang@linux.intel.com> wrote: > > Only when SPARSEMEM_VMEMMAP is set, memmap returned from > section_activate() points to sub-section page struct. Otherwise, memmap > already points to the whole section page struct. > > This means only for SPARSEMEM_VMEMMAP, we need to adjust memmap for > sub-section case. > > Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") > Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> > CC: Dan Williams <dan.j.williams@intel.com> > --- > mm/sparse.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 586d85662978..b5da121bdd6e 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -886,7 +886,8 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, > section_mark_present(ms); > > /* Align memmap to section boundary in the subsection case */ > - if (section_nr_to_pfn(section_nr) != start_pfn) > + if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && > + section_nr_to_pfn(section_nr) != start_pfn) Aren't we assured that start_pfn is always section aligned in the SPARSEMEM case? That's the role of check_pfn_span(). Does the change have a runtime impact or is this just theoretical?
On Thu, Feb 06, 2020 at 06:00:13PM -0800, Dan Williams wrote: >On Thu, Feb 6, 2020 at 3:17 PM Wei Yang <richardw.yang@linux.intel.com> wrote: >> >> Only when SPARSEMEM_VMEMMAP is set, memmap returned from >> section_activate() points to sub-section page struct. Otherwise, memmap >> already points to the whole section page struct. >> >> This means only for SPARSEMEM_VMEMMAP, we need to adjust memmap for >> sub-section case. >> >> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> >> CC: Dan Williams <dan.j.williams@intel.com> >> --- >> mm/sparse.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/mm/sparse.c b/mm/sparse.c >> index 586d85662978..b5da121bdd6e 100644 >> --- a/mm/sparse.c >> +++ b/mm/sparse.c >> @@ -886,7 +886,8 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, >> section_mark_present(ms); >> >> /* Align memmap to section boundary in the subsection case */ >> - if (section_nr_to_pfn(section_nr) != start_pfn) >> + if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && >> + section_nr_to_pfn(section_nr) != start_pfn) > >Aren't we assured that start_pfn is always section aligned in the >SPARSEMEM case? That's the role of check_pfn_span(). Does the change >have a runtime impact or is this just theoretical? You are right, I missed this point. Thanks
diff --git a/mm/sparse.c b/mm/sparse.c index 586d85662978..b5da121bdd6e 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -886,7 +886,8 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn, section_mark_present(ms); /* Align memmap to section boundary in the subsection case */ - if (section_nr_to_pfn(section_nr) != start_pfn) + if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && + section_nr_to_pfn(section_nr) != start_pfn) memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr)); sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
Only when SPARSEMEM_VMEMMAP is set, memmap returned from section_activate() points to sub-section page struct. Otherwise, memmap already points to the whole section page struct. This means only for SPARSEMEM_VMEMMAP, we need to adjust memmap for sub-section case. Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") Signed-off-by: Wei Yang <richardw.yang@linux.intel.com> CC: Dan Williams <dan.j.williams@intel.com> --- mm/sparse.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)