btrfs: tree-checker: reject file extent items for special files

File extent items are only utilized by regular files or symlinks, other
files like directory/char/block/FIFO/sock files should not have any file
extent item.

Previously we were unable to reject such cases, as the inode item may not
be in the same leaf.
But we already have @prev_key in check_leaf_item(), this means we just
need a new way to pass the mode of the previously hit inode item, then
we can detect such problems.

Introduce a new helper structure, saved_inode_info, to record the inode
number and its mode hit in the same leaf, and keep it across the whole
leaf.
Then if we hit a file extent item, and the inode item is in the same
leaf, we can refer to that to determine if we need to reject the file
extent item.

Now with the following corrupted fs tree, the kernel can safely reject
the leaf:

	item 0 key (256 INODE_ITEM 0) itemoff 16123 itemsize 160
		generation 3 transid 9 size 12 nbytes 16384
		block group 0 mode 40755 links 1 uid 0 gid 0 rdev 0
		sequence 1 flags 0x0(none)
	item 1 key (256 INODE_REF 256) itemoff 16111 itemsize 12
		index 0 namelen 2 name: ..
	item 2 key (256 DIR_ITEM 496027801) itemoff 16075 itemsize 36
		location key (257 INODE_ITEM 0) type FILE
		transid 9 data_len 0 name_len 6
		name: foobar
	item 3 key (256 DIR_INDEX 2) itemoff 16039 itemsize 36
		location key (257 INODE_ITEM 0) type FILE
		transid 9 data_len 0 name_len 6
		name: foobar
	item 4 key (257 INODE_ITEM 0) itemoff 15879 itemsize 160
		generation 9 transid 9 size 8192 nbytes 8192
		block group 0 mode 60600 links 1 uid 0 gid 0 rdev 0
		                   ^^ This is BLK type, not REG.
		sequence 2 flags 0x0(none)
	item 5 key (257 INODE_REF 256) itemoff 15863 itemsize 16
		index 2 namelen 6 name: foobar
	item 6 key (257 EXTENT_DATA 0) itemoff 15810 itemsize 53
		generation 9 type 1 (regular)
		extent data disk byte 13631488 nr 8192
		extent data offset 0 nr 8192 ram 8192
		extent compression 0 (none)
		extent encryption 0

With the patch, kernel will reject it with the following tree-checker
errors:

  BTRFS critical (device loop0): corrupt leaf: root=5 block=30408704 slot=6 ino=257 file_offset=0, unexpected file extent item type 1 for inode mode 060600
  BTRFS error (device loop0): read time tree block corruption detected on logical 30408704 mirror 1

Reported-by: ZhengYuan Huang <gality369@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/20260817132051.267646-1-gality369@gmail.com/
Assisted-by: LLM (for generating the corrupted image)
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

0 files changed, 0 insertions, 0 deletions