On Mon, Jun 19, 2023 at 03:22:20PM +0800, mawupeng wrote: > > > On 2023/6/19 15:16, Greg KH wrote: > > On Mon, Jun 19, 2023 at 02:51:21PM +0800, Wupeng Ma wrote: > >> From: David Hildenbrand <david@xxxxxxxxxx> > >> > >> commit 8dc4bb58a146655eb057247d7c9d19e73928715b upstream. > >> > >> virtio-mem soon wants to use offline_and_remove_memory() memory that > >> exceeds a single Linux memory block (memory_block_size_bytes()). Let's > >> remove that restriction. > >> > >> Let's remember the old state and try to restore that if anything goes > >> wrong. While re-onlining can, in general, fail, it's highly unlikely to > >> happen (usually only when a notifier fails to allocate memory, and these > >> are rather rare). > >> > >> This will be used by virtio-mem to offline+remove memory ranges that are > >> bigger than a single memory block - for example, with a device block > >> size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory > >> block size of 128MB. > >> > >> While we could compress the state into 2 bit, using 8 bit is much > >> easier. > >> > >> This handling is similar, but different to acpi_scan_try_to_offline(): > >> > >> a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG > >> optimization is still relevant - it should only apply to ZONE_NORMAL > >> (where we have no guarantees). If relevant, we can always add it. > >> > >> b) acpi_scan_try_to_offline() simply onlines all memory in case > >> something goes wrong. It doesn't restore previous online type. Let's do > >> that, so we won't overwrite what e.g., user space configured. > >> > >> Reviewed-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> > >> Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx> > >> Cc: Jason Wang <jasowang@xxxxxxxxxx> > >> Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx> > >> Cc: Michal Hocko <mhocko@xxxxxxxxxx> > >> Cc: Oscar Salvador <osalvador@xxxxxxx> > >> Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> > >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > >> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> > >> Link: https://lore.kernel.org/r/20201112133815.13332-28-david@xxxxxxxxxx > >> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> > >> Acked-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > >> Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> > >> --- > >> mm/memory_hotplug.c | 105 +++++++++++++++++++++++++++++++++++++------- > >> 1 file changed, 89 insertions(+), 16 deletions(-) > >> > > > > Why is this needed in 5.10.y? Looks like a new feature to me, what > > problem does it solve there? > > > > thanks, > > > > greg k-h > > It do introduce a new feature. But at the same time, it fix a memleak introduced > in Commit 08b3acd7a68f ("mm/memory_hotplug: Introduce offline_and_remove_memory()" > > Our test find a memleak in init_memory_block, it is clear that mem is never > been released due to wrong refcount. Commit 08b3acd7a68f ("mm/memory_hotplug: > Introduce offline_and_remove_memory()") failed to dec refcount after > find_memory_block which fail to dec refcount to zero in remove memory > causing the leak. > > Commit 8dc4bb58a146 ("mm/memory_hotplug: extend offline_and_remove_memory() > to handle more than one memory block") introduce walk_memory_blocks to > replace find_memory_block which dec refcount by calling put_device after > find_memory_block_by_id. In the way, the memleak is fixed. > > Here is the simplified calltrace: > > kmem_cache_alloc_trace+0x664/0xed0 > init_memory_block+0x8c/0x170 > create_memory_block_devices+0xa4/0x150 > add_memory_resource+0x188/0x530 > __add_memory+0x78/0x104 > add_memory+0x6c/0xb0 Ok, thanks for the information, now queued up. greg k-h
