Re: [PATCH 2/8] mm/memory_hotplug: fix error handling in add_memory_resource()

David Hildenbrand
2023-11-14T18:36:30Z

On 14.11.23 19:02, Sumanth Korikkar wrote:
> In add_memory_resource(), creation of memory block devices occurs after
> successful call to arch_add_memory(). However, creation of memory block
> devices could fail. In that case, arch_remove_memory() is called to
> perform necessary cleanup.
>
> Currently with or without altmap support, arch_remove_memory() is always
> passed with altmap set to NULL during error handling. This leads to
> freeing of struct pages using free_pages(), eventhough the allocation
> might have been performed with altmap support via
> altmap_alloc_block_buf().
>
> Fix the error handling by passing altmap in arch_remove_memory(). This
> ensures the following:
> * When altmap is disabled, deallocation of the struct pages array occurs
> via free_pages().
> * When altmap is enabled, deallocation occurs via vmem_altmap_free().
>
> Fixes: db051a0dac13 ("mm/memory_hotplug: create memory block devices after arch_add_memory()")

That's the wrong commit. We didn't support memmap-on-memory back then.

Likely it should be:

Fixes: a08a2ae34613 ("mm,memory_hotplug: allocate memmap from the added
memory range")

> Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> Signed-off-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
> ---
> mm/memory_hotplug.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index c8238fc5edcb..4f476a970e84 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1458,7 +1458,7 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> /* create memory block devices after memory was added */
> ret = create_memory_block_devices(start, size, params.altmap, group);
> if (ret) {
> - arch_remove_memory(start, size, NULL);
> + arch_remove_memory(start, size, params.altmap);
> goto error_free;
> }
>

Indeed; this will conflict with Vishals patches, ccing him.

--
Cheers,

David / dhildenb