Re: [Xen-devel] [PATCH v1 1/6] mm/memory_hotplug: make remove_memory() take the device_hotplug_lock

["Rafael J. Wysocki" <rafael@xxxxxxxxxx>]

On Tue, Sep 18, 2018 at 1:48 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> remove_memory() is exported right now but requires the
> device_hotplug_lock, which is not exported. So let's provide a variant
> that takes the lock and only export that one.
>
> The lock is already held in
>         arch/powerpc/platforms/pseries/hotplug-memory.c
>         drivers/acpi/acpi_memhotplug.c
> So, let's use the locked variant.
>
> The lock is not held (but taken in)
>         arch/powerpc/platforms/powernv/memtrace.c
> So let's keep using the (now) locked variant.
>
> Apart from that, there are not other users in the tree.
>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Len Brown <lenb@xxxxxxxxxx>
> Cc: Rashmica Gupta <rashmica.g@xxxxxxxxx>
> Cc: Michael Neuling <mikey@xxxxxxxxxxx>
> Cc: Balbir Singh <bsingharora@xxxxxxxxx>
> Cc: Nathan Fontenot <nfont@xxxxxxxxxxxxxxxxxx>
> Cc: John Allen <jallen@xxxxxxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Michal Hocko <mhocko@xxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> Cc: Vlastimil Babka <vbabka@xxxxxxx>
> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Oscar Salvador <osalvador@xxxxxxx>
> Cc: YASUAKI ISHIMATSU <yasu.isimatu@xxxxxxxxx>
> Cc: Mathieu Malaterre <malat@xxxxxxxxxx>
> Reviewed-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
>  arch/powerpc/platforms/powernv/memtrace.c       | 2 --
>  arch/powerpc/platforms/pseries/hotplug-memory.c | 6 +++---
>  drivers/acpi/acpi_memhotplug.c                  | 2 +-
>  include/linux/memory_hotplug.h                  | 3 ++-
>  mm/memory_hotplug.c                             | 9 ++++++++-
>  5 files changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c 
> b/arch/powerpc/platforms/powernv/memtrace.c
> index 51dc398ae3f7..8f1cd4f3bfd5 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -90,9 +90,7 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, 
> u64 nr_pages)
>         walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
>                           change_memblock_state);
>
> -       lock_device_hotplug();
>         remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
> -       unlock_device_hotplug();
>
>         return true;
>  }
> diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c 
> b/arch/powerpc/platforms/pseries/hotplug-memory.c
> index c1578f54c626..b3f54466e25f 100644
> --- a/arch/powerpc/platforms/pseries/hotplug-memory.c
> +++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
> @@ -334,7 +334,7 @@ static int pseries_remove_memblock(unsigned long base, 
> unsigned int memblock_siz
>         nid = memory_add_physaddr_to_nid(base);
>
>         for (i = 0; i < sections_per_block; i++) {
> -               remove_memory(nid, base, MIN_MEMORY_BLOCK_SIZE);
> +               __remove_memory(nid, base, MIN_MEMORY_BLOCK_SIZE);
>                 base += MIN_MEMORY_BLOCK_SIZE;
>         }
>
> @@ -423,7 +423,7 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
>         block_sz = pseries_memory_block_size();
>         nid = memory_add_physaddr_to_nid(lmb->base_addr);
>
> -       remove_memory(nid, lmb->base_addr, block_sz);
> +       __remove_memory(nid, lmb->base_addr, block_sz);
>
>         /* Update memory regions for memory remove */
>         memblock_remove(lmb->base_addr, block_sz);
> @@ -710,7 +710,7 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
>
>         rc = dlpar_online_lmb(lmb);
>         if (rc) {
> -               remove_memory(nid, lmb->base_addr, block_sz);
> +               __remove_memory(nid, lmb->base_addr, block_sz);
>                 dlpar_remove_device_tree_lmb(lmb);
>         } else {
>                 lmb->flags |= DRCONF_MEM_ASSIGNED;
> diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
> index 6b0d3ef7309c..811148415993 100644
> --- a/drivers/acpi/acpi_memhotplug.c
> +++ b/drivers/acpi/acpi_memhotplug.c
> @@ -282,7 +282,7 @@ static void acpi_memory_remove_memory(struct 
> acpi_memory_device *mem_device)
>                         nid = memory_add_physaddr_to_nid(info->start_addr);
>
>                 acpi_unbind_memory_blocks(info);
> -               remove_memory(nid, info->start_addr, info->length);
> +               __remove_memory(nid, info->start_addr, info->length);
>                 list_del(&info->list);
>                 kfree(info);
>         }
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 34a28227068d..1f096852f479 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -301,6 +301,7 @@ extern bool is_mem_section_removable(unsigned long pfn, 
> unsigned long nr_pages);
>  extern void try_offline_node(int nid);
>  extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
>  extern void remove_memory(int nid, u64 start, u64 size);
> +extern void __remove_memory(int nid, u64 start, u64 size);
>
>  #else
>  static inline bool is_mem_section_removable(unsigned long pfn,
> @@ -317,6 +318,7 @@ static inline int offline_pages(unsigned long start_pfn, 
> unsigned long nr_pages)
>  }
>
>  static inline void remove_memory(int nid, u64 start, u64 size) {}
> +static inline void __remove_memory(int nid, u64 start, u64 size) {}
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
>
>  extern void __ref free_area_init_core_hotplug(int nid);
> @@ -330,7 +332,6 @@ extern void move_pfn_range_to_zone(struct zone *zone, 
> unsigned long start_pfn,
>                 unsigned long nr_pages, struct vmem_altmap *altmap);
>  extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
>  extern bool is_memblock_offlined(struct memory_block *mem);
> -extern void remove_memory(int nid, u64 start, u64 size);
>  extern int sparse_add_one_section(struct pglist_data *pgdat,
>                 unsigned long start_pfn, struct vmem_altmap *altmap);
>  extern void sparse_remove_one_section(struct zone *zone, struct mem_section 
> *ms,
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 38d94b703e9d..b8b1bd970322 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1873,7 +1873,7 @@ EXPORT_SYMBOL(try_offline_node);
>   * and online/offline operations before this call, as required by
>   * try_offline_node().
>   */
> -void __ref remove_memory(int nid, u64 start, u64 size)
> +void __ref __remove_memory(int nid, u64 start, u64 size)
>  {
>         int ret;
>
> @@ -1902,5 +1902,12 @@ void __ref remove_memory(int nid, u64 start, u64 size)
>
>         mem_hotplug_done();
>  }
> +
> +void remove_memory(int nid, u64 start, u64 size)
> +{
> +       lock_device_hotplug();
> +       __remove_memory(nid, start, size);
> +       unlock_device_hotplug();
> +}
>  EXPORT_SYMBOL_GPL(remove_memory);
>  #endif /* CONFIG_MEMORY_HOTREMOVE */
> --

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

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