commit 1dae7e0e58b484eaa43d530f211098fdeeb0f404 upstream.
[BUG] There are several reported runaway balance, that balance is flooding the log with "found X extents" where the X never changes.
[CAUSE] Commit d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") introduced BTRFS_ROOT_DEAD_RELOC_TREE bit to indicate that one subvolume has finished its tree blocks swap with its reloc tree.
However if balance is canceled or hits ENOSPC halfway, we didn't clear the BTRFS_ROOT_DEAD_RELOC_TREE bit, leaving that bit hanging forever until unmount.
Any subvolume root with that bit, would cause backref cache to skip this tree block, as it has finished its tree block swap. This would cause all tree blocks of that root be ignored by balance, leading to runaway balance.
[FIX] Fix the problem by also clearing the BTRFS_ROOT_DEAD_RELOC_TREE bit for the original subvolume of orphan reloc root.
Add an umount check for the stale bit still set.
Fixes: d2311e698578 ("btrfs: relocation: Delay reloc tree deletion after merge_reloc_roots") Cc: stable@vger.kernel.org # 5.4.x Signed-off-by: Qu Wenruo wqu@suse.com [Manually solve the conflicts due to no btrfs root refs rework] Signed-off-by: David Sterba dsterba@suse.com --- fs/btrfs/relocation.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 3f8c706d75ee..1b087ee338cc 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -2540,6 +2540,8 @@ void merge_reloc_roots(struct reloc_control *rc) if (!IS_ERR(root)) { if (root->reloc_root == reloc_root) root->reloc_root = NULL; + clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, + &root->state); }
list_del_init(&reloc_root->root_list);