On Tue, Jan 28, 2020 at 10:49:57AM +0100, David Hildenbrand wrote:
This is the backport of the following fixes for 4.19-stable:
- d84f2f5a7552 ("drivers/base/node.c: simplify unregister_memory_block_under_nodes()")
-- Turned out to not only be a cleanup but also a fix
- 2c91f8fc6c99 ("mm/memory_hotplug: fix try_offline_node()")
-- Automatic stable backport failed due to missing dependencies.
- feee6b298916 ("mm/memory_hotplug: shrink zones when offlining memory")
-- Was marked as stable 5.0+ due to the backport complexity,, but it's also relevant for 4.19/4.14. As I have to backport quite some cleanups already ...
All tackle memory unplug issues, especially when memory was never onlined (or onlining failed), paired with memory unplug. When trying to access garbage memmaps we crash the kernel (e.g., because the derviced pgdat pointer is broken)
To minimize manual code changes, I decided to pull in quite some cleanups. Still some manual code changes are necessary (indicated in the individual patches). Especially missing arm64 hot(un)plug, missing sub-section hotadd support, and missing unification of mm/hmm.c and kernel/memremap.c requires care.
Due to:
- 4e0d2e7ef14d ("mm, sparse: pass nid instead of pgdat to sparse_add_one_section()")
I need:
- afe9b36ca890 ("mm/memunmap: don't access uninitialized memmap in memunmap_pages()")
Please note that:
- 4c4b7f9ba948 ("mm/memory_hotplug: remove memory block devices before arch_remove_memory()")
Makes big (e.g., 32TB) machines boot up slower (e.g., 2h vs 10m). There is a performance fix in linux-next, but it does not seem to classify as a fix for current RC / stable.
If this is that big of a regression, yes, it does classify as a fix and is ok for the stable trees. Please let me know what that git id is when it hits Linus's tree.
I did quite some testing with hot(un)plug, onlining/offlining of memory blocks and memory-less/CPU-less NUMA nodes under x86_64 - the same set of tests I run against upstream on a fairly regular basis. I compile-tested on PowerPC, arm64, s390x, i386 and sh. I did not test any ZONE_DEVICE/HMM thingies.
The 4.14 backport might take a bit - it would be quite a lot of patches to backport and it is not that severely broken, so I am thinking about simpler (less invasive) alternatives.
All now queued up, thanks.
greg k-h