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, 90 insertions, 0 deletions

diff --git a/include/scsi/scsi_dh.h b/include/scsi/scsi_dh.h
new file mode 100644
index 000000000..4df943c1b
--- /dev/null
+++ b/include/scsi/scsi_dh.h
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Header file for SCSI device handler infrastructure.
+ *
+ * Modified version of patches posted by Mike Christie <michaelc@cs.wisc.edu>
+ *
+ * Copyright IBM Corporation, 2007
+ *      Authors:
+ *               Chandra Seetharaman <sekharan@us.ibm.com>
+ *               Mike Anderson <andmike@linux.vnet.ibm.com>
+ */
+
+#include <scsi/scsi_device.h>
+
+enum {
+	SCSI_DH_OK = 0,
+	/*
+	 * device errors
+	 */
+	SCSI_DH_DEV_FAILED,	/* generic device error */
+	SCSI_DH_DEV_TEMP_BUSY,
+	SCSI_DH_DEV_UNSUPP,	/* device handler not supported */
+	SCSI_DH_DEVICE_MAX,	/* max device blkerr definition */
+
+	/*
+	 * transport errors
+	 */
+	SCSI_DH_NOTCONN = SCSI_DH_DEVICE_MAX + 1,
+	SCSI_DH_CONN_FAILURE,
+	SCSI_DH_TRANSPORT_MAX,	/* max transport blkerr definition */
+
+	/*
+	 * driver and generic errors
+	 */
+	SCSI_DH_IO = SCSI_DH_TRANSPORT_MAX + 1,	/* generic error */
+	SCSI_DH_INVALID_IO,
+	SCSI_DH_RETRY,		/* retry the req, but not immediately */
+	SCSI_DH_IMM_RETRY,	/* immediately retry the req */
+	SCSI_DH_TIMED_OUT,
+	SCSI_DH_RES_TEMP_UNAVAIL,
+	SCSI_DH_DEV_OFFLINED,
+	SCSI_DH_NOMEM,
+	SCSI_DH_NOSYS,
+	SCSI_DH_DRIVER_MAX,
+};
+
+typedef void (*activate_complete)(void *, int);
+struct scsi_device_handler {
+	/* Used by the infrastructure */
+	struct list_head list; /* list of scsi_device_handlers */
+
+	/* Filled by the hardware handler */
+	struct module *module;
+	const char *name;
+	enum scsi_disposition (*check_sense)(struct scsi_device *,
+					     struct scsi_sense_hdr *);
+	int (*attach)(struct scsi_device *);
+	void (*detach)(struct scsi_device *);
+	int (*activate)(struct scsi_device *, activate_complete, void *);
+	blk_status_t (*prep_fn)(struct scsi_device *, struct request *);
+	int (*set_params)(struct scsi_device *, const char *);
+	void (*rescan)(struct scsi_device *);
+};
+
+#ifdef CONFIG_SCSI_DH
+extern int scsi_dh_activate(struct request_queue *, activate_complete, void *);
+extern int scsi_dh_attach(struct request_queue *, const char *);
+extern const char *scsi_dh_attached_handler_name(struct request_queue *, gfp_t);
+extern int scsi_dh_set_params(struct request_queue *, const char *);
+#else
+static inline int scsi_dh_activate(struct request_queue *req,
+					activate_complete fn, void *data)
+{
+	fn(data, 0);
+	return 0;
+}
+static inline int scsi_dh_attach(struct request_queue *req, const char *name)
+{
+	return SCSI_DH_NOSYS;
+}
+static inline const char *scsi_dh_attached_handler_name(struct request_queue *q,
+							gfp_t gfp)
+{
+	return NULL;
+}
+static inline int scsi_dh_set_params(struct request_queue *req, const char *params)
+{
+	return -SCSI_DH_NOSYS;
+}
+#endif