[PATCH v8 35/39] btrfs: do not panic in __add_reloc_root

[Josef Bacik]

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 <jo...@toxicpanda.com>
---
 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 2fc04f96294e..857da684d415 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) {
                btrfs_put_root(reloc_root);
                return ret;
@@ -4054,6 +4056,7 @@ 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);
@@ -4274,6 +4277,7 @@ 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) {
                btrfs_put_root(reloc_root);
                return ret;
-- 
2.26.2