[PATCH 5.10.y 3/5] btrfs: do not panic in __add_reloc_root

[Sasha Levin <sashal@kernel.org>]

From: Josef Bacik <josef@toxicpanda.com>

[ Upstream commit 57a304cfd43b2b4a5b44b8f5dc026abb34183068 ]

If we have a duplicate entry for a reloc root then we could have fs
corruption that resulted in a double allocation.  Since this shouldn't
happen unless there is corruption, add an ASSERT(ret != -EEXIST) to all
of the callers of __add_reloc_root() to catch any logic mistakes for
developers, otherwise normal error handling will happen for normal
users.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Stable-dep-of: 6d8ba4572922 ("btrfs: drop recovered reloc root refs on recovery failure")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/btrfs/relocation.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 8ac37034c6561..0442cfe70b323 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -638,9 +638,10 @@ static int __must_check __add_reloc_root(struct btrfs_root *root)
 				   node->bytenr, &node->rb_node);
 	spin_unlock(&rc->reloc_root_tree.lock);
 	if (rb_node) {
-		btrfs_panic(fs_info, -EEXIST,
+		btrfs_err(fs_info,
 			    "Duplicate root found for start=%llu while inserting into relocation tree",
 			    node->bytenr);
+		return -EEXIST;
 	}
 
 	list_add_tail(&root->root_list, &rc->reloc_roots);
@@ -882,6 +883,7 @@ int btrfs_init_reloc_root(struct btrfs_trans_handle *trans,
 		return PTR_ERR(reloc_root);
 
 	ret = __add_reloc_root(reloc_root);
+	ASSERT(ret != -EEXIST);
 	if (ret) {
 		/* Pairs with create_reloc_root */
 		btrfs_put_root(reloc_root);
@@ -3862,6 +3864,7 @@ int btrfs_recover_relocation(struct btrfs_root *root)
 		}
 
 		err = __add_reloc_root(reloc_root);
+		ASSERT(err != -EEXIST);
 		if (err) {
 			list_add_tail(&reloc_root->root_list, &reloc_roots);
 			btrfs_put_root(fs_root);
@@ -4092,6 +4095,7 @@ int btrfs_reloc_post_snapshot(struct btrfs_trans_handle *trans,
 		return PTR_ERR(reloc_root);
 
 	ret = __add_reloc_root(reloc_root);
+	ASSERT(ret != -EEXIST);
 	if (ret) {
 		/* Pairs with create_reloc_root */
 		btrfs_put_root(reloc_root);
-- 
2.53.0