On 09/16/2019 12:06 PM, Mike Rapoport wrote: > On Mon, Sep 16, 2019 at 11:17:37AM +0530, Anshuman Khandual wrote: >> In add_memory_resource() the memory range to be hot added first gets into >> the memblock via memblock_add() before arch_add_memory() is called on it. >> Reverse sequence should be followed during memory hot removal which already >> is being followed in add_memory_resource() error path. This now ensures >> required re-order between memblock_[free|remove]() and arch_remove_memory() >> during memory hot-remove. >> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: Oscar Salvador <osalvador@xxxxxxx> >> Cc: Michal Hocko <mhocko@xxxxxxxx> >> Cc: David Hildenbrand <david@xxxxxxxxxx> >> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> >> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> >> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> >> --- >> Original patch https://lkml.org/lkml/2019/9/3/327 >> >> Memory hot remove now works on arm64 without this because a recent commit >> 60bb462fc7ad ("drivers/base/node.c: simplify unregister_memory_block_under_nodes()"). >> >> David mentioned that re-ordering should still make sense for consistency >> purpose (removing stuff in the reverse order they were added). This patch >> is now detached from arm64 hot-remove series. >> >> https://lkml.org/lkml/2019/9/3/326 >> >> mm/memory_hotplug.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >> index c73f09913165..355c466e0621 100644 >> --- a/mm/memory_hotplug.c >> +++ b/mm/memory_hotplug.c >> @@ -1770,13 +1770,13 @@ static int __ref try_remove_memory(int nid, u64 start, u64 size) >> >> /* remove memmap entry */ >> firmware_map_remove(start, start + size, "System RAM"); >> - memblock_free(start, size); >> - memblock_remove(start, size); >> >> /* remove memory block devices before removing memory */ >> remove_memory_block_devices(start, size); >> >> arch_remove_memory(nid, start, size, NULL); >> + memblock_free(start, size); > > I don't see memblock_reserve() anywhere in memory_hotplug.c, so the > memblock_free() call here seems superfluous. I think it can be simply > dropped. I had observed that previously but was not sure whether or not there are still scenarios where it might be true. Error path in add_memory_resource() even just calls memblock_remove() not memblock_free(). Unless there is any objection, can just drop it.
