On 02/06/20 at 02:26am, Wei Yang wrote: > On Thu, Feb 06, 2020 at 08:37:36AM +0800, Baoquan He wrote: > >On 02/06/20 at 08:13am, Baoquan He wrote: > >> On 02/06/20 at 07:50am, Wei Yang wrote: > >> > On Thu, Feb 06, 2020 at 07:19:45AM +0800, Wei Yang wrote: > >> > >On Wed, Feb 05, 2020 at 02:52:51PM +0100, David Hildenbrand wrote: > >> > >>Let's use a calculation that's easier to understand and calculates the > >> > >>same result. Reusing existing macros makes this look nicer. > >> > >> > >> > >>We always want to have the number of pages (> 0) to the next section > >> > >>boundary, starting from the current pfn. > >> > >> > >> > >>Suggested-by: Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> > >> > >>Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > >> > >>Cc: Michal Hocko <mhocko@xxxxxxxxxx> > >> > >>Cc: Oscar Salvador <osalvador@xxxxxxx> > >> > >>Cc: Baoquan He <bhe@xxxxxxxxxx> > >> > >>Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> > >> > >>Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > >> > > > >> > >Reviewed-by: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx> > >> > > > >> > >BTW, I got one question about hotplug size requirement. > >> > > > >> > >I thought the hotplug range should be section size aligned, while taking a > >> > >look into current code function check_hotplug_memory_range() guard the range. > >> > >> A good question. The current code should be block size aligned. I > >> remember in some places we assume each block comprise all the sections. > >> Can't imagine one or some of them are half section filled. > > > >I could be wrong, half filled block may not cause problem. > > > > David must be angry about our flooding the mail list :-) Believe he won't, :-) If you like, we can talk off line. > > Check the code again, there are two memory range check: > > * check_hotplug_memory_range(), block/section aligned > * check_pfn_span(), subsection aligned > > The second check, check_pfn_span() in __add_pages(), enable the capability to > add a memory range with subsection size. > > This means hotplug still keeps section alignment. memremap_pages() also call add_pages(), it doesn't have the check_hotplug_memory_range() invocation. check_pfn_span() is made for it specifically. > > BTW, __add_pages() share the same logic as __remove_pages(). Why not change it > too? Do I miss something or I don't have the latest source code? Good question, and I think it need. Just David is refactoring/cleaning up the remove_pages() code path, this is found out by Segher from patch reviewing.
