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, 203 insertions, 0 deletions

diff --git a/fs/bfs/file.c b/fs/bfs/file.c
new file mode 100644
index 000000000..d33d6bde9
--- /dev/null
+++ b/fs/bfs/file.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *	fs/bfs/file.c
+ *	BFS file operations.
+ *	Copyright (C) 1999-2018 Tigran Aivazian <aivazian.tigran@gmail.com>
+ *
+ *	Make the file block allocation algorithm understand the size
+ *	of the underlying block device.
+ *	Copyright (C) 2007 Dmitri Vorobiev <dmitri.vorobiev@gmail.com>
+ *
+ */
+
+#include <linux/fs.h>
+#include <linux/mpage.h>
+#include <linux/buffer_head.h>
+#include "bfs.h"
+
+#undef DEBUG
+
+#ifdef DEBUG
+#define dprintf(x...)	printf(x)
+#else
+#define dprintf(x...)
+#endif
+
+const struct file_operations bfs_file_operations = {
+	.llseek 	= generic_file_llseek,
+	.read_iter	= generic_file_read_iter,
+	.write_iter	= generic_file_write_iter,
+	.mmap_prepare	= generic_file_mmap_prepare,
+	.splice_read	= filemap_splice_read,
+};
+
+static int bfs_move_block(unsigned long from, unsigned long to,
+					struct super_block *sb)
+{
+	struct buffer_head *bh, *new;
+
+	bh = sb_bread(sb, from);
+	if (!bh)
+		return -EIO;
+	new = sb_getblk(sb, to);
+	memcpy(new->b_data, bh->b_data, bh->b_size);
+	mark_buffer_dirty(new);
+	bforget(bh);
+	brelse(new);
+	return 0;
+}
+
+static int bfs_move_blocks(struct super_block *sb, unsigned long start,
+				unsigned long end, unsigned long where)
+{
+	unsigned long i;
+
+	dprintf("%08lx-%08lx->%08lx\n", start, end, where);
+	for (i = start; i <= end; i++)
+		if(bfs_move_block(i, where + i, sb)) {
+			dprintf("failed to move block %08lx -> %08lx\n", i,
+								where + i);
+			return -EIO;
+		}
+	return 0;
+}
+
+static int bfs_get_block(struct inode *inode, sector_t block,
+			struct buffer_head *bh_result, int create)
+{
+	unsigned long phys;
+	int err;
+	struct super_block *sb = inode->i_sb;
+	struct bfs_sb_info *info = BFS_SB(sb);
+	struct bfs_inode_info *bi = BFS_I(inode);
+
+	phys = bi->i_sblock + block;
+	if (!create) {
+		if (phys <= bi->i_eblock) {
+			dprintf("c=%d, b=%08lx, phys=%09lx (granted)\n",
+                                create, (unsigned long)block, phys);
+			map_bh(bh_result, sb, phys);
+		}
+		return 0;
+	}
+
+	/*
+	 * If the file is not empty and the requested block is within the
+	 * range of blocks allocated for this file, we can grant it.
+	 */
+	if (bi->i_sblock && (phys <= bi->i_eblock)) {
+		dprintf("c=%d, b=%08lx, phys=%08lx (interim block granted)\n", 
+				create, (unsigned long)block, phys);
+		map_bh(bh_result, sb, phys);
+		return 0;
+	}
+
+	/* The file will be extended, so let's see if there is enough space. */
+	if (phys >= info->si_blocks)
+		return -ENOSPC;
+
+	/* The rest has to be protected against itself. */
+	mutex_lock(&info->bfs_lock);
+
+	/*
+	 * If the last data block for this file is the last allocated
+	 * block, we can extend the file trivially, without moving it
+	 * anywhere.
+	 */
+	if (bi->i_eblock == info->si_lf_eblk) {
+		dprintf("c=%d, b=%08lx, phys=%08lx (simple extension)\n", 
+				create, (unsigned long)block, phys);
+		map_bh(bh_result, sb, phys);
+		info->si_freeb -= phys - bi->i_eblock;
+		info->si_lf_eblk = bi->i_eblock = phys;
+		mark_inode_dirty(inode);
+		err = 0;
+		goto out;
+	}
+
+	/* Ok, we have to move this entire file to the next free block. */
+	phys = info->si_lf_eblk + 1;
+	if (phys + block >= info->si_blocks) {
+		err = -ENOSPC;
+		goto out;
+	}
+
+	if (bi->i_sblock) {
+		err = bfs_move_blocks(inode->i_sb, bi->i_sblock, 
+						bi->i_eblock, phys);
+		if (err) {
+			dprintf("failed to move ino=%08lx -> fs corruption\n",
+								inode->i_ino);
+			goto out;
+		}
+	} else
+		err = 0;
+
+	dprintf("c=%d, b=%08lx, phys=%08lx (moved)\n",
+                create, (unsigned long)block, phys);
+	bi->i_sblock = phys;
+	phys += block;
+	info->si_lf_eblk = bi->i_eblock = phys;
+
+	/*
+	 * This assumes nothing can write the inode back while we are here
+	 * and thus update inode->i_blocks! (XXX)
+	 */
+	info->si_freeb -= bi->i_eblock - bi->i_sblock + 1 - inode->i_blocks;
+	mark_inode_dirty(inode);
+	map_bh(bh_result, sb, phys);
+out:
+	mutex_unlock(&info->bfs_lock);
+	return err;
+}
+
+static int bfs_writepages(struct address_space *mapping,
+		struct writeback_control *wbc)
+{
+	return mpage_writepages(mapping, wbc, bfs_get_block);
+}
+
+static int bfs_read_folio(struct file *file, struct folio *folio)
+{
+	return block_read_full_folio(folio, bfs_get_block);
+}
+
+static void bfs_write_failed(struct address_space *mapping, loff_t to)
+{
+	struct inode *inode = mapping->host;
+
+	if (to > inode->i_size)
+		truncate_pagecache(inode, inode->i_size);
+}
+
+static int bfs_write_begin(const struct kiocb *iocb,
+			   struct address_space *mapping,
+			   loff_t pos, unsigned len,
+			   struct folio **foliop, void **fsdata)
+{
+	int ret;
+
+	ret = block_write_begin(mapping, pos, len, foliop, bfs_get_block);
+	if (unlikely(ret))
+		bfs_write_failed(mapping, pos + len);
+
+	return ret;
+}
+
+static sector_t bfs_bmap(struct address_space *mapping, sector_t block)
+{
+	return generic_block_bmap(mapping, block, bfs_get_block);
+}
+
+const struct address_space_operations bfs_aops = {
+	.dirty_folio	= block_dirty_folio,
+	.invalidate_folio = block_invalidate_folio,
+	.read_folio	= bfs_read_folio,
+	.writepages	= bfs_writepages,
+	.write_begin	= bfs_write_begin,
+	.write_end	= generic_write_end,
+	.migrate_folio	= buffer_migrate_folio,
+	.bmap		= bfs_bmap,
+};
+
+const struct inode_operations bfs_file_inops;