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Subject: [PATCH] btrfs: debug block device parameters before reading superblock
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Debug patch to understand NULL pointer dereference in create_empty_buffers.
Print logical_block_size and mapping_min_folio_order to identify the correct
check needed.

NOT FOR MERGE - debug only.

Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 fs/btrfs/volumes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 13c514684cfb..40de5be63172 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1341,6 +1341,9 @@ struct btrfs_super_block *btrfs_read_disk_super(struct block_device *bdev,
 	struct address_space *mapping = bdev->bd_mapping;
 	int ret;
 
+	pr_err("DEBUG btrfs: logical_block_size=%u min_folio_order=%u\n",
+		 bdev_logical_block_size(bdev),
+		mapping_min_folio_order(mapping));
 	bytenr_orig = btrfs_sb_offset(copy_num);
 	ret = btrfs_sb_log_location_bdev(bdev, copy_num, READ, &bytenr);
 	if (ret < 0) {
-- 
2.43.0