x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 28 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-numa b/Documentation/ABI/testing/sysfs-kernel-mm-numa
new file mode 100644
index 000000000..90e375ff5
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-numa
@@ -0,0 +1,28 @@
+What:		/sys/kernel/mm/numa/
+Date:		June 2021
+Contact:	Linux memory management mailing list <linux-mm@kvack.org>
+Description:	Interface for NUMA
+
+What:		/sys/kernel/mm/numa/demotion_enabled
+Date:		June 2021
+Contact:	Linux memory management mailing list <linux-mm@kvack.org>
+Description:	Enable/disable demoting pages during reclaim
+
+		Page migration during reclaim is intended for systems
+		with tiered memory configurations.  These systems have
+		multiple types of memory with varied performance
+		characteristics instead of plain NUMA systems where
+		the same kind of memory is found at varied distances.
+		Allowing page migration during reclaim enables these
+		systems to migrate pages from fast tiers to slow tiers
+		when the fast tier is under pressure.  This migration
+		is performed before swap if an eligible numa node is
+		present in cpuset.mems for the cgroup (or if cpuset v1
+		is being used). If cpusets.mems changes at runtime, it
+		may move data to a NUMA node that does not fall into the
+		cpuset of the new cpusets.mems, which might be construed
+		to violate the guarantees of cpusets.  Shared memory,
+		such as libraries, owned by another cgroup may still be
+		demoted and result in memory use on a node not present
+		in cpusets.mem. This should not be enabled on systems
+		which need strict cpuset location guarantees.