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, 59 insertions, 0 deletions

diff --git a/Documentation/block/error-injection.rst b/Documentation/block/error-injection.rst
new file mode 100644
index 000000000..81f31af82
--- /dev/null
+++ b/Documentation/block/error-injection.rst
@@ -0,0 +1,59 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================
+Configurable Error Injection
+============================
+
+Overview
+--------
+
+Configurable error injection allows injecting specific block layer status codes
+for sector ranges of a block device.  Errors can be injected unconditionally, or
+with a given probability.
+
+To use configurable error injection, CONFIG_BLK_ERROR_INJECTION must be enabled.
+
+The only interface is the error_injection debugfs file, which is created for
+each registered gendisk.  Writes to this file are used to create or delete rules
+and reads return a list of the current error injection sites.
+
+Options
+-------
+
+The following options specify the operations:
+
+===================	=======================================================
+add			add a new rule
+removeall		remove all existing rules
+===================	=======================================================
+
+The following options specify the details of the rule for the add operation:
+
+===================	=======================================================
+op=<string>		block layer operation this rule applies to.  This uses
+			the XYZ for each REQ_OP_XYZ operation, e.g. READ, WRITE
+			or DISCARD. Mandatory.
+status=<string>		Status to return.  This uses XYZ for each BLK_STS_XYZ
+			code, e.g. IOERR or MEDIUM. Mandatory.
+start=<number>		First block layer sector the rule applies to.
+			Optional, defaults to 0.
+nr_sectors=<number>	Number of sectors this rule applies.
+			Optional, defaults to the remainder of the device.
+chance=<number>		Only return a failure with a likelihood of 1/chance.
+			Optional, defaults to 1 (always).
+===================	=======================================================
+
+Example
+-------
+
+Return BLK_STS_IOERR for one in 10 reads of sector 0 of /dev/nvme0n1:
+
+	$ echo 'add,op=READ,start=0,status=IOERR,chance=10' > /sys/kernel/debug/block/nvme0n1/error_injection
+
+Return BLK_STS_MEDIUM for every write to /dev/nvme0n1:
+
+	$ echo 'add,op=WRITE,start=0,status=MEDIUM' > /sys/kernel/debug/block/nvme0n1/error_injection
+
+Remove all rules for /dev/nvme0n1:
+
+	$ echo 'removeall' > /sys/kernel/debug/block/nvme0n1/error_injection