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, 88 insertions, 0 deletions

diff --git a/drivers/md/dm-cache-background-tracker.h b/drivers/md/dm-cache-background-tracker.h
new file mode 100644
index 000000000..47156c14a
--- /dev/null
+++ b/drivers/md/dm-cache-background-tracker.h
@@ -0,0 +1,88 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2017 Red Hat. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#ifndef DM_CACHE_BACKGROUND_WORK_H
+#define DM_CACHE_BACKGROUND_WORK_H
+
+#include <linux/vmalloc.h>
+#include "dm-cache-policy.h"
+
+/*----------------------------------------------------------------*/
+
+/*
+ * The cache policy decides what background work should be performed,
+ * such as promotions, demotions and writebacks. The core cache target
+ * is in charge of performing the work, and does so when it sees fit.
+ *
+ * The background_tracker acts as a go between. Keeping track of future
+ * work that the policy has decided upon, and handing (issuing) it to
+ * the core target when requested.
+ *
+ * There is no locking in this, so calls will probably need to be
+ * protected with a spinlock.
+ */
+
+struct bt_work {
+	struct list_head list;
+	struct rb_node node;
+	struct policy_work work;
+};
+
+extern struct kmem_cache *btracker_work_cache;
+
+struct background_work;
+struct background_tracker;
+
+/*
+ * Create a new tracker, it will not be able to queue more than
+ * 'max_work' entries.
+ */
+struct background_tracker *btracker_create(unsigned int max_work);
+
+/*
+ * Destroy the tracker. No issued, but not complete, work should
+ * exist when this is called. It is fine to have queued but unissued
+ * work.
+ */
+void btracker_destroy(struct background_tracker *b);
+
+unsigned int btracker_nr_demotions_queued(struct background_tracker *b);
+
+/*
+ * Queue some work within the tracker. 'work' should point to the work
+ * to queue, this will be copied (ownership doesn't pass).  If pwork
+ * is not NULL then it will be set to point to the tracker's internal
+ * copy of the work.
+ *
+ * returns -EINVAL iff the work is already queued.  -ENOMEM if the work
+ * couldn't be queued for another reason.
+ */
+int btracker_queue(struct background_tracker *b,
+		   struct policy_work *work,
+		   struct policy_work **pwork);
+
+/*
+ * Hands out the next piece of work to be performed.
+ * Returns -ENODATA if there's no work.
+ */
+int btracker_issue(struct background_tracker *b, struct policy_work **work);
+
+/*
+ * Informs the tracker that the work has been completed and it may forget
+ * about it.
+ */
+void btracker_complete(struct background_tracker *b, struct policy_work *op);
+
+/*
+ * Predicate to see if an origin block is already scheduled for promotion.
+ */
+bool btracker_promotion_already_present(struct background_tracker *b,
+					dm_oblock_t oblock);
+
+/*----------------------------------------------------------------*/
+
+#endif