[BUG]
There is one report about `btrfs rescue clear-ino-cache` failed with
tree block level mismatch:
# btrfs rescue clear-ino-cache /dev/mapper/rootext
Successfully cleaned up ino cache for root id: 5
Successfully cleaned up ino cache for root id: 257
Successfully cleaned up ino cache for root id: 258
corrupt node: root=7 block=647369064448 slot=0, invalid level for leaf, have 1 expect 0
node 647369064448 level 1 items 252 free space 241 generation 6065173 owner CSUM_TREE
node 647369064448 flags 0x1(WRITTEN) backref revision 1
fs uuid e6614f01-6f56-4776-8b0a-c260089c35e7
chunk uuid f665f535-4cfd-49e0-8be9-7f94bf59b75d
key (EXTENT_CSUM EXTENT_CSUM 3714473984) block 677126111232 gen 6065002
[...]
key (EXTENT_CSUM EXTENT_CSUM 6192357376) block 646396493824 gen 6065032
ERROR: failed to clear ino cache: Input/output error
[CAUSE]
During `btrfs rescue clear-ino-cache`, btrfs-progs will iterate through
all the subvolumes, and clear the inode cache inode from each subvolume.
The problem is in how we iterate the subvolumes.
We hold a path of tree root, and go modifiy the fs for each found
subvolume, then call btrfs_next_item().
This is not safe, because the path to tree root is not longer reliable
if we modified the fs.
So the btrfs_next_item() call will fail because the fs is modified
halfway, resulting the above problem.
[FIX]
Instead of holding a path to a subvolume root item, and modify the fs
halfway, here introduce a helper, find_next_root(), to locate the root
item whose objectid >= our target rootid, and return the found item key.
The path to root tree is only hold then released inside
find_next_root().
By this, we won't hold any unrelated path while modifying the
filesystem.
And since we're here, also adding back the missing new line when all ino
cache is cleared.
Pull-request: #890
Reported-by: Archange <archange@archlinux.org>
Link: https://lore.kernel.org/linux-btrfs/4803f696-2dc5-4987-a353-fce1272e93e7@archlinux.org/
Signed-off-by: Qu Wenruo <wqu@suse.com>
85225ea00a