[Xen-devel] [PATCH v2 5/6] powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages()

[David Hildenbrand <david@xxxxxxxxxx>]

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();
                if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) {
                        /*
                         * Remove memory in memory block size chunks so that
@@ -118,7 +120,6 @@ static u64 memtrace_alloc_node(u32 nid, u64 size)
                         * we never try to remove memory that spans two iomem
                         * resources.
                         */
-                       lock_device_hotplug();
                        end_pfn = base_pfn + nr_pages;
                        for (pfn = base_pfn; pfn < end_pfn; pfn += bytes>> 
PAGE_SHIFT) {
                                __remove_memory(nid, pfn << PAGE_SHIFT, bytes);
@@ -126,6 +127,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size)
                        unlock_device_hotplug();
                        return base_pfn << PAGE_SHIFT;
                }
+               unlock_device_hotplug();
        }
 
        return 0;
-- 
2.17.1


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