[PATCH AUTOSEL 4.19 005/100] powerpc/powernv: hold device_hotplug_lock when calling memtrace_offline_pages()

From: David Hildenbrand <redacted>

[ Upstream commit 5666848774ef43d3db5151ec518f1deb63515c20 ]

Let's perform all checking + offlining + removing under
device_hotplug_lock, so nobody can mess with these devices via sysfs
concurrently.

[david@redhat.com: take device_hotplug_lock outside of loop]
  Link: http://lkml.kernel.org/r/20180927092554.13567-6-david@redhat.com
Link: http://lkml.kernel.org/r/20180925091457.28651-6-david@redhat.com
Signed-off-by: David Hildenbrand <redacted>
Reviewed-by: Pavel Tatashin <redacted>
Reviewed-by: Rashmica Gupta <redacted>
Acked-by: Balbir Singh <bsingharora@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Rashmica Gupta <redacted>
Cc: Michael Neuling <redacted>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dan Williams <redacted>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Heiko Carstens <redacted>
Cc: John Allen <redacted>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Joonsoo Kim <redacted>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kate Stewart <redacted>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Martin Schwidefsky <redacted>
Cc: Mathieu Malaterre <redacted>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nathan Fontenot <redacted>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Philippe Ombredanne <redacted>
Cc: Rafael J. Wysocki <redacted>
Cc: "Rafael J. Wysocki" <redacted>
Cc: Stephen Hemminger <redacted>
Cc: Thomas Gleixner <redacted>
Cc: Vlastimil Babka <redacted>
Cc: YASUAKI ISHIMATSU <redacted>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 a29fdf8a2e56e..232bf5987f91d 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;

@@ -110,6 +111,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size)
 	/* Trace memory needs to be aligned to the size */
 	end_pfn = round_down(end_pfn - nr_pages, nr_pages);
 
+	lock_device_hotplug();
 	for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) {
 		if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) {
 			/*

@@ -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);

@@ -127,6 +128,7 @@ static u64 memtrace_alloc_node(u32 nid, u64 size)
 			return base_pfn << PAGE_SHIFT;
 		}
 	}
+	unlock_device_hotplug();
 
 	return 0;
 }

-- 
2.20.1