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, 75 insertions, 0 deletions

diff --git a/drivers/scsi/scsi_debugfs.c b/drivers/scsi/scsi_debugfs.c
new file mode 100644
index 000000000..eb52e39f3
--- /dev/null
+++ b/drivers/scsi/scsi_debugfs.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/seq_file.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_dbg.h>
+#include <scsi/scsi_host.h>
+#include "scsi_debugfs.h"
+
+#define SCSI_CMD_FLAG_NAME(name)[const_ilog2(SCMD_##name)] = #name
+static const char *const scsi_cmd_flags[] = {
+	SCSI_CMD_FLAG_NAME(TAGGED),
+	SCSI_CMD_FLAG_NAME(INITIALIZED),
+	SCSI_CMD_FLAG_NAME(LAST),
+};
+#undef SCSI_CMD_FLAG_NAME
+
+static int scsi_flags_show(struct seq_file *m, const unsigned long flags,
+			   const char *const *flag_name, int flag_name_count)
+{
+	bool sep = false;
+	int i;
+
+	for_each_set_bit(i, &flags, BITS_PER_LONG) {
+		if (sep)
+			seq_puts(m, "|");
+		sep = true;
+		if (i < flag_name_count && flag_name[i])
+			seq_puts(m, flag_name[i]);
+		else
+			seq_printf(m, "%d", i);
+	}
+	return 0;
+}
+
+static const char *scsi_cmd_list_info(struct scsi_cmnd *cmd)
+{
+	struct Scsi_Host *shost = cmd->device->host;
+	struct scsi_cmnd *cmd2;
+
+	guard(spinlock_irq)(shost->host_lock);
+
+	list_for_each_entry(cmd2, &shost->eh_abort_list, eh_entry)
+		if (cmd == cmd2)
+			return "on eh_abort_list";
+
+	list_for_each_entry(cmd2, &shost->eh_cmd_q, eh_entry)
+		if (cmd == cmd2)
+			return "on eh_cmd_q";
+
+	return NULL;
+}
+
+void scsi_show_rq(struct seq_file *m, struct request *rq)
+{
+	struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(rq);
+	int alloc_ms = jiffies_to_msecs(jiffies - cmd->jiffies_at_alloc);
+	int timeout_ms = jiffies_to_msecs(rq->timeout);
+	char buf[80] = "(?)";
+
+	if (cmd->flags & SCMD_INITIALIZED) {
+		const char *list_info = scsi_cmd_list_info(cmd);
+
+		__scsi_format_command(buf, sizeof(buf), cmd->cmnd, cmd->cmd_len);
+		seq_printf(m, ", .cmd=%s, .retries=%d, .allowed=%d, .result = %#x%s%s",
+			   buf, cmd->retries, cmd->allowed, cmd->result,
+			   list_info ? ", " : "", list_info ? : "");
+		seq_printf(m, ", .timeout=%d.%03d, allocated %d.%03d s ago",
+			   timeout_ms / 1000, timeout_ms % 1000,
+			   alloc_ms / 1000, alloc_ms % 1000);
+	}
+	seq_printf(m, ", .flags=");
+	scsi_flags_show(m, cmd->flags, scsi_cmd_flags,
+			ARRAY_SIZE(scsi_cmd_flags));
+}