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Date:   Tue, 21 Aug 2018 12:44:17 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
        xen-devel@...ts.xenproject.org, devel@...uxdriverproject.org,
        David Hildenbrand <david@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Rashmica Gupta <rashmica.g@...il.com>,
        Balbir Singh <bsingharora@...il.com>,
        Michael Neuling <mikey@...ling.org>
Subject: [PATCH RFCv2 5/6] powerpc/powernv: hold device_hotplug_lock in memtrace_offline_pages()

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@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Rashmica Gupta <rashmica.g@...il.com>
Cc: Balbir Singh <bsingharora@...il.com>
Cc: Michael Neuling <mikey@...ling.org>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 arch/powerpc/platforms/powernv/memtrace.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c
index ef7181d4fe68..473e59842ec5 100644
--- a/arch/powerpc/platforms/powernv/memtrace.c
+++ b/arch/powerpc/platforms/powernv/memtrace.c
@@ -74,9 +74,13 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
 {
 	u64 end_pfn = start_pfn + nr_pages - 1;
 
+	lock_device_hotplug();
+
 	if (walk_memory_range(start_pfn, end_pfn, NULL,
-	    check_memblock_online))
+	    check_memblock_online)) {
+		unlock_device_hotplug();
 		return false;
+	}
 
 	walk_memory_range(start_pfn, end_pfn, (void *)MEM_GOING_OFFLINE,
 			  change_memblock_state);
@@ -84,14 +88,16 @@ static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages)
 	if (offline_pages(start_pfn, nr_pages)) {
 		walk_memory_range(start_pfn, end_pfn, (void *)MEM_ONLINE,
 				  change_memblock_state);
+		unlock_device_hotplug();
 		return false;
 	}
 
 	walk_memory_range(start_pfn, end_pfn, (void *)MEM_OFFLINE,
 			  change_memblock_state);
 
-	remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
+	__remove_memory(nid, start_pfn << PAGE_SHIFT, nr_pages << PAGE_SHIFT);
 
+	unlock_device_hotplug();
 	return true;
 }
 
-- 
2.17.1

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