On 04/09/18 at 09:02am, Dave Hansen wrote: > On 04/07/2018 11:50 PM, Baoquan He wrote: > >> Should the " = 0" instead be clearing SECTION_MARKED_PRESENT or > >> something? That would make it easier to match the code up with the code > >> that it is effectively undoing. > > > > Not sure if I understand your question correctly. From memory_present(), > > information encoded into ms->section_mem_map including numa node, > > SECTION_IS_ONLINE and SECTION_MARKED_PRESENT. Not sure if it's OK to only > > clear SECTION_MARKED_PRESENT. People may wrongly check SECTION_IS_ONLINE > > and do something on this memory section? > > What is mean is that, instead of: I mean that in memory_present() all present sections are marked with below information. ms->section_mem_map = (nid << SECTION_NID_SHIFT) | SECTION_MARKED_PRESENT | SECTION_IS_ONLINE; Later in sparse_init(), if we failed to allocate mem map, the corresponding section need clear its ->section_mem_map. The existing code does the clearing with: ms->section_mem_map = 0; If with 'ms->section_mem_map &= ~SECTION_MARKED_PRESENT', the nid and SECTION_IS_ONLINE are still left in ms->section_mem_map. Someone may probably mistakenly check if this section is online and do something, or still get nid from this section. Just worried. > > > ms->section_mem_map = 0; > > we could literally do: > > ms->section_mem_map &= ~SECTION_MARKED_PRESENT; > > That does the same thing in practice, but makes the _intent_ much more > clear.
