| Message ID | 20200206231629.14151-4-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: > > In case of SPARSEMEM, populate_section_memmap() would allocate memmap > for the whole section, even we just want a sub-section. This would lead > to memmap overwrite if we a sub-section to an already populated section. > > Just return the populated memmap for non-SPARSEMEM_VMEMMAP 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 | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 56816f653588..c75ca40db513 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -836,6 +836,16 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, > if (nr_pages < PAGES_PER_SECTION && early_section(ms)) > return pfn_to_page(pfn); > > + /* > + * If it is not SPARSEMEM_VMEMMAP, we always populate memmap for the > + * whole section, even for a sub-section. > + * > + * Return its memmap if already populated to avoid memmap overwrite. > + */ > + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && > + valid_section(ms)) > + return __section_mem_map_addr(ms); Again, is check_pfn_span() failing to prevent this path?
On 02/06/20 at 06:06pm, Dan Williams wrote: > On Thu, Feb 6, 2020 at 3:17 PM Wei Yang <richardw.yang@linux.intel.com> wrote: > > > > In case of SPARSEMEM, populate_section_memmap() would allocate memmap > > for the whole section, even we just want a sub-section. This would lead > > to memmap overwrite if we a sub-section to an already populated section. > > > > Just return the populated memmap for non-SPARSEMEM_VMEMMAP 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 | 10 ++++++++++ > > 1 file changed, 10 insertions(+) > > > > diff --git a/mm/sparse.c b/mm/sparse.c > > index 56816f653588..c75ca40db513 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -836,6 +836,16 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, > > if (nr_pages < PAGES_PER_SECTION && early_section(ms)) > > return pfn_to_page(pfn); > > > > + /* > > + * If it is not SPARSEMEM_VMEMMAP, we always populate memmap for the > > + * whole section, even for a sub-section. > > + * > > + * Return its memmap if already populated to avoid memmap overwrite. > > + */ > > + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && > > + valid_section(ms)) > > + return __section_mem_map_addr(ms); > > Again, is check_pfn_span() failing to prevent this path? The answer should be yes, this patch is not needed. >
On Thu, Feb 06, 2020 at 06:06:54PM -0800, Dan Williams wrote: >On Thu, Feb 6, 2020 at 3:17 PM Wei Yang <richardw.yang@linux.intel.com> wrote: >> >> In case of SPARSEMEM, populate_section_memmap() would allocate memmap >> for the whole section, even we just want a sub-section. This would lead >> to memmap overwrite if we a sub-section to an already populated section. >> >> Just return the populated memmap for non-SPARSEMEM_VMEMMAP 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 | 10 ++++++++++ >> 1 file changed, 10 insertions(+) >> >> diff --git a/mm/sparse.c b/mm/sparse.c >> index 56816f653588..c75ca40db513 100644 >> --- a/mm/sparse.c >> +++ b/mm/sparse.c >> @@ -836,6 +836,16 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, >> if (nr_pages < PAGES_PER_SECTION && early_section(ms)) >> return pfn_to_page(pfn); >> >> + /* >> + * If it is not SPARSEMEM_VMEMMAP, we always populate memmap for the >> + * whole section, even for a sub-section. >> + * >> + * Return its memmap if already populated to avoid memmap overwrite. >> + */ >> + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && >> + valid_section(ms)) >> + return __section_mem_map_addr(ms); > >Again, is check_pfn_span() failing to prevent this path? Oh, you are right. Thanks
diff --git a/mm/sparse.c b/mm/sparse.c index 56816f653588..c75ca40db513 100644 --- a/mm/sparse.c +++ b/mm/sparse.c @@ -836,6 +836,16 @@ static struct page * __meminit section_activate(int nid, unsigned long pfn, if (nr_pages < PAGES_PER_SECTION && early_section(ms)) return pfn_to_page(pfn); + /* + * If it is not SPARSEMEM_VMEMMAP, we always populate memmap for the + * whole section, even for a sub-section. + * + * Return its memmap if already populated to avoid memmap overwrite. + */ + if (!IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) && + valid_section(ms)) + return __section_mem_map_addr(ms); + memmap = populate_section_memmap(pfn, nr_pages, nid, altmap); if (!memmap) { section_deactivate(pfn, nr_pages, altmap);
In case of SPARSEMEM, populate_section_memmap() would allocate memmap for the whole section, even we just want a sub-section. This would lead to memmap overwrite if we a sub-section to an already populated section. Just return the populated memmap for non-SPARSEMEM_VMEMMAP 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 | 10 ++++++++++ 1 file changed, 10 insertions(+)