On Tue, Sep 25, 2018 at 11:14:56AM +0200, David Hildenbrand wrote:
> Let's perform all checking + offlining + removing under
> device_hotplug_lock, so nobody can mess with these devices via
> sysfs concurrently.
>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Rashmica Gupta <rashmica.g@xxxxxxxxx>
> Cc: Balbir Singh <bsingharora@xxxxxxxxx>
> Cc: Michael Neuling <mikey@xxxxxxxxxxx>
> Reviewed-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx>
> Reviewed-by: Rashmica Gupta <rashmica.g@xxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
> ---
> arch/powerpc/platforms/powernv/memtrace.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
> index fdd48f1a39f7..d84d09c56af9 100644
> --- a/arch/powerpc/platforms/powernv/memtrace.c
> +++ b/arch/powerpc/platforms/powernv/memtrace.c
> @@ -70,6 +70,7 @@ static int change_memblock_state(struct memory_block *mem, void *arg)
> return 0;
> }
>
> +/* called with device_hotplug_lock held */
> static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
> {
> u64 end_pfn = start_pfn + nr_pages - 1;
> @@ -111,6 +112,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size)
> end_pfn = round_down(end_pfn - nr_pages, nr_pages);
>
> for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) {
> + lock_device_hotplug();
Why not grab the lock before the for loop? That way we can avoid bad cases like a
large node being scanned for a small number of pages (nr_pages). Ideally we need
a cond_resched() in the loop, but I guess offline_pages() has one.
Acked-by: Balbir Singh <bsingharora@xxxxxxxxx>
