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, 61 insertions, 0 deletions

diff --git a/drivers/md/dm-pcache/segment.c b/drivers/md/dm-pcache/segment.c
new file mode 100644
index 000000000..8f8816e1c
--- /dev/null
+++ b/drivers/md/dm-pcache/segment.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/dax.h>
+
+#include "pcache_internal.h"
+#include "cache_dev.h"
+#include "segment.h"
+
+int segment_copy_to_bio(struct pcache_segment *segment,
+		u32 data_off, u32 data_len, struct bio *bio, u32 bio_off)
+{
+	struct iov_iter iter;
+	size_t copied;
+	void *src;
+
+	iov_iter_bvec(&iter, ITER_DEST, &bio->bi_io_vec[bio->bi_iter.bi_idx],
+			bio_segments(bio), bio->bi_iter.bi_size);
+	iter.iov_offset = bio->bi_iter.bi_offset;
+	if (bio_off)
+		iov_iter_advance(&iter, bio_off);
+
+	src = segment->data + data_off;
+	copied = _copy_mc_to_iter(src, data_len, &iter);
+	if (copied != data_len)
+		return -EIO;
+
+	return 0;
+}
+
+int segment_copy_from_bio(struct pcache_segment *segment,
+		u32 data_off, u32 data_len, struct bio *bio, u32 bio_off)
+{
+	struct iov_iter iter;
+	size_t copied;
+	void *dst;
+
+	iov_iter_bvec(&iter, ITER_SOURCE, &bio->bi_io_vec[bio->bi_iter.bi_idx],
+			bio_segments(bio), bio->bi_iter.bi_size);
+	iter.iov_offset = bio->bi_iter.bi_offset;
+	if (bio_off)
+		iov_iter_advance(&iter, bio_off);
+
+	dst = segment->data + data_off;
+	copied = _copy_from_iter_flushcache(dst, data_len, &iter);
+	if (copied != data_len)
+		return -EIO;
+	pmem_wmb();
+
+	return 0;
+}
+
+void pcache_segment_init(struct pcache_cache_dev *cache_dev, struct pcache_segment *segment,
+		      struct pcache_segment_init_options *options)
+{
+	segment->seg_info = options->seg_info;
+	segment_info_set_type(segment->seg_info, options->type);
+
+	segment->cache_dev = cache_dev;
+	segment->seg_id = options->seg_id;
+	segment->data_size = PCACHE_SEG_SIZE - options->data_off;
+	segment->data = CACHE_DEV_SEGMENT(cache_dev, options->seg_id) + options->data_off;
+}