[BUG]
There is one BUG_ON() report where a transaction is aborted during
balance, then kernel BUG_ON() in merge_reloc_roots():
void merge_reloc_roots(struct reloc_control *rc)
{
...
BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root)); <<<
}
[CAUSE]
It's still uncertain why we can get to such situation.
As all __add_reloc_root() calls will also link that reloc root to
rc->reloc_roots, and in merge_reloc_roots() we cleanup rc->reloc_roots.
So the root cause is still uncertain.
[FIX]
But we can still hunt down all the BUG_ON() in merge_reloc_roots().
There are 3 BUG_ON()s in it:
- BUG_ON() for read_fs_root() result
- BUG_ON() for root->reloc_root != reloc_root case
- BUG_ON() for the non-empty reloc_root_tree
For the first two, just grab the return value and goto out tag for
cleanup.
For the last one, make it more graceful by:
- grab the lock before doing read/write
- warn instead of panic
- cleanup the nodes in rc->reloc_root_tree
Signed-off-by: Qu Wenruo <w...@suse.com>
---
Reason for RFC:
The root cause to leak nodes in reloc_root_tree is still unknown.
---
fs/btrfs/relocation.c | 39 ++++++++++++++++++++++++++++++++++++---
1 file changed, 36 insertions(+), 3 deletions(-)
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index 655f1d5a8c27..d562b5c52a40 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -2484,11 +2484,26 @@ void merge_reloc_roots(struct reloc_control *rc)
if (btrfs_root_refs(&reloc_root->root_item) > 0) {
root = read_fs_root(fs_info,
reloc_root->root_key.offset);
- BUG_ON(IS_ERR(root));
- BUG_ON(root->reloc_root != reloc_root);
+ if (IS_ERR(root)) {
+ ret = PTR_ERR(root);
+ btrfs_err(fs_info,
+ "failed to read root %llu: %d",
+ reloc_root->root_key.offset, ret);
+ goto out;
+ }
+ if (root->reloc_root != reloc_root) {
+ btrfs_err(fs_info,
+ "reloc root mismatch for root %llu",
+ root->root_key.objectid);
+ ret = -EINVAL;
+ goto out;
+ }
ret = merge_reloc_root(rc, root);
if (ret) {
+ btrfs_err(fs_info,
+ "failed to merge reloc tree for root %llu: %d",
+ root->root_key.objectid, ret);
if (list_empty(&reloc_root->root_list))
list_add_tail(&reloc_root->root_list,
&reloc_roots);
@@ -2520,7 +2535,25 @@ void merge_reloc_roots(struct reloc_control *rc)
free_reloc_roots(&reloc_roots);
}
- BUG_ON(!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root));
+ spin_lock(&rc->reloc_root_tree.lock);
+ /* Cleanup dirty reloc tree nodes */
+ if (!RB_EMPTY_ROOT(&rc->reloc_root_tree.rb_root)) {
+ struct mapping_node *node;
+ struct mapping_node *next;
+
+ WARN_ON(IS_ENABLED(CONFIG_BTRFS_DEBUG));
+ rbtree_postorder_for_each_entry_safe(node, next,
+ &rc->reloc_root_tree.rb_root, rb_node) {
+ struct btrfs_root *root = node->data;
+
+ if (root)
+ btrfs_debug(fs_info,
+ "root %llu still in rc->reloc_root_tree",
+ root->root_key.offset);
+ kfree(node);
+ }
+ }
+ spin_unlock(&rc->reloc_root_tree.lock);
}
static void free_block_list(struct rb_root *blocks)
--
2.23.0
