| Message ID | 161058500148.1840162.4365921007820501696.stgit@dwillia2-desk3.amr.corp.intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: Fix pfn_to_online_page() with respect to ZONE_DEVICE | expand |
On Wed 13-01-21 16:43:21, Dan Williams wrote: > pfn_section_valid() determines pfn validity on subsection granularity > where pfn_valid() may be limited to coarse section granularity. > Explicitly validate subsections after pfn_valid() succeeds. The changelog is not really clear on the underlying problem. It would benefit from some clarification. What about something like this? " pfn_to_online_page is primarily used to filter out offline or fully uninitialized pages. pfn_valid resp. online_section_nr have a coarse per memory section granularity. If a section shared with a partially offline memory (e.g. part of ZONE_DEVICE) then pfn_to_online_page would lead to a false positive on some pfns. Fix this by adding pfn_section_valid check which is subsection aware. " > > Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()") > Cc: Qian Cai <cai@lca.pw> > Cc: Michal Hocko <mhocko@suse.com> > Cc: Oscar Salvador <osalvador@suse.de> > Reported-by: David Hildenbrand <david@redhat.com> > Reviewed-by: David Hildenbrand <david@redhat.com> > Reviewed-by: Oscar Salvador <osalvador@suse.de> > Signed-off-by: Dan Williams <dan.j.williams@intel.com> With that feel free to add Acked-by: Michal Hocko <mhocko@suse.com> > --- > mm/memory_hotplug.c | 23 +++++++++++++++++++---- > 1 file changed, 19 insertions(+), 4 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 55a69d4396e7..d0c81f7a3347 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -308,11 +308,26 @@ static int check_hotplug_memory_addressable(unsigned long pfn, > struct page *pfn_to_online_page(unsigned long pfn) > { > unsigned long nr = pfn_to_section_nr(pfn); > + struct mem_section *ms; > + > + if (nr >= NR_MEM_SECTIONS) > + return NULL; > + > + ms = __nr_to_section(nr); > + if (!online_section(ms)) > + return NULL; > + > + /* > + * Save some code text when online_section() + > + * pfn_section_valid() are sufficient. > + */ > + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) && !pfn_valid(pfn)) > + return NULL; > + > + if (!pfn_section_valid(ms, pfn)) > + return NULL; > > - if (nr < NR_MEM_SECTIONS && online_section_nr(nr) && > - pfn_valid_within(pfn)) > - return pfn_to_page(pfn); > - return NULL; > + return pfn_to_page(pfn); > } > EXPORT_SYMBOL_GPL(pfn_to_online_page); > >
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 55a69d4396e7..d0c81f7a3347 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -308,11 +308,26 @@ static int check_hotplug_memory_addressable(unsigned long pfn, struct page *pfn_to_online_page(unsigned long pfn) { unsigned long nr = pfn_to_section_nr(pfn); + struct mem_section *ms; + + if (nr >= NR_MEM_SECTIONS) + return NULL; + + ms = __nr_to_section(nr); + if (!online_section(ms)) + return NULL; + + /* + * Save some code text when online_section() + + * pfn_section_valid() are sufficient. + */ + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) && !pfn_valid(pfn)) + return NULL; + + if (!pfn_section_valid(ms, pfn)) + return NULL; - if (nr < NR_MEM_SECTIONS && online_section_nr(nr) && - pfn_valid_within(pfn)) - return pfn_to_page(pfn); - return NULL; + return pfn_to_page(pfn); } EXPORT_SYMBOL_GPL(pfn_to_online_page);
pfn_section_valid() determines pfn validity on subsection granularity where pfn_valid() may be limited to coarse section granularity. Explicitly validate subsections after pfn_valid() succeeds. Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()") Cc: Qian Cai <cai@lca.pw> Cc: Michal Hocko <mhocko@suse.com> Cc: Oscar Salvador <osalvador@suse.de> Reported-by: David Hildenbrand <david@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Oscar Salvador <osalvador@suse.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com> --- mm/memory_hotplug.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-)