The patch titled Subject: mm/memory_hotplug: replace an open-coded kmemdup() in add_memory_resource() has been added to the -mm mm-unstable branch. Its filename is mm-memory_hotplug-replace-an-open-coded-kmemdup-in-add_memory_resource.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory_hotplug-replace-an-open-coded-kmemdup-in-add_memory_resource.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Vishal Verma <vishal.l.verma@xxxxxxxxx> Subject: mm/memory_hotplug: replace an open-coded kmemdup() in add_memory_resource() Date: Tue, 07 Nov 2023 00:22:41 -0700 Patch series "mm: use memmap_on_memory semantics for dax/kmem", v10. The dax/kmem driver can potentially hot-add large amounts of memory originating from CXL memory expanders, or NVDIMMs, or other 'device memories'. There is a chance there isn't enough regular system memory available to fit the memmap for this new memory. It's therefore desirable, if all other conditions are met, for the kmem managed memory to place its memmap on the newly added memory itself. The main hurdle for accomplishing this for kmem is that memmap_on_memory can only be done if the memory being added is equal to the size of one memblock. To overcome this, allow the hotplug code to split an add_memory() request into memblock-sized chunks, and try_remove_memory() to also expect and handle such a scenario. Patch 1 replaces an open-coded kmemdup() Patch 2 teaches the memory_hotplug code to allow for splitting add_memory() and remove_memory() requests over memblock sized chunks. Patch 3 allows the dax region drivers to request memmap_on_memory semantics. CXL dax regions default this to 'on', all others default to off to keep existing behavior unchanged. This patch (of 3): A review of the memmap_on_memory modifications to add_memory_resource() revealed an instance of an open-coded kmemdup(). Replace it with kmemdup(). Link: https://lkml.kernel.org/r/20231107-vv-kmem_memmap-v10-0-1253ec050ed0@xxxxxxxxx Link: https://lkml.kernel.org/r/20231107-vv-kmem_memmap-v10-1-1253ec050ed0@xxxxxxxxx Signed-off-by: Vishal Verma <vishal.l.verma@xxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Fan Ni <fan.ni@xxxxxxxxxxx> Reported-by: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Dave Jiang <dave.jiang@xxxxxxxxx> Cc: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> Cc: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memory_hotplug.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/mm/memory_hotplug.c~mm-memory_hotplug-replace-an-open-coded-kmemdup-in-add_memory_resource +++ a/mm/memory_hotplug.c @@ -1439,13 +1439,13 @@ int __ref add_memory_resource(int nid, s if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { if (mhp_supports_memmap_on_memory(size)) { mhp_altmap.free = memory_block_memmap_on_memory_pages(); - params.altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL); + params.altmap = kmemdup(&mhp_altmap, + sizeof(struct vmem_altmap), + GFP_KERNEL); if (!params.altmap) { ret = -ENOMEM; goto error; } - - memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap)); } /* fallback to not using altmap */ } _ Patches currently in -mm which might be from vishal.l.verma@xxxxxxxxx are mm-memory_hotplug-replace-an-open-coded-kmemdup-in-add_memory_resource.patch mm-memory_hotplug-split-memmap_on_memory-requests-across-memblocks.patch dax-kmem-allow-kmem-to-add-memory-with-memmap_on_memory.patch