[PATCH 3/3] btrfs: report missing raid stripe tree root during lookup

When rescue=ibadroots ignores a failure to load the raid stripe tree root,
fs_info->stripe_root remains NULL. After the rescue mount proceeds, reading
file data that requires the raid stripe tree reaches
btrfs_get_raid_extent_offset().

Currently btrfs_search_slot() handles the NULL root and returns -EINVAL.
This avoids a NULL pointer dereference, but provides no diagnostic and
incorrectly describes missing filesystem metadata as an invalid argument.

Check stripe_root before allocating a path, emit a rate-limited error with
the logical address, and return -EUCLEAN.

Lookups with a valid stripe root are unchanged.

Signed-off-by: Dongjiang Zhu <[email protected]>
---
 fs/btrfs/raid-stripe-tree.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c
index 454a95bf542a..716ba7cbce17 100644
--- a/fs/btrfs/raid-stripe-tree.c
+++ b/fs/btrfs/raid-stripe-tree.c
@@ -414,6 +414,13 @@ int btrfs_get_raid_extent_offset(struct btrfs_fs_info *fs_info,
 	int slot;
 	int ret;
 
+	if (unlikely(!stripe_root)) {
+		btrfs_err_rl(fs_info,
+			     "missing raid stripe tree root for logical %llu",
+			     logical);
+		return -EUCLEAN;
+	}
+
 	stripe_key.objectid = logical;
 	stripe_key.type = BTRFS_RAID_STRIPE_KEY;
 	stripe_key.offset = 0;
-- 
2.39.5