From 1dae7e0e58b484eaa43d530f211098fdeeb0f404 Mon Sep 17 00:00:00 2001 From: Qu Wenruo Date: Wed, 20 May 2020 14:58:51 +0800 Subject: [PATCH] btrfs: reloc: clear DEAD_RELOC_TREE bit for orphan roots to prevent runaway balance [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") Signed-off-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/disk-io.c | 1 + fs/btrfs/relocation.c | 2 ++ 2 files changed, 3 insertions(+) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index f1143741f6ba..7b66a8e4ca54 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1994,6 +1994,7 @@ void btrfs_put_root(struct btrfs_root *root) if (refcount_dec_and_test(&root->refs)) { WARN_ON(!RB_EMPTY_ROOT(&root->inode_tree)); + WARN_ON(test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)); if (root->anon_dev) free_anon_bdev(root->anon_dev); btrfs_drew_lock_destroy(&root->snapshot_lock); diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index 81b076e46143..68dd7a771e5e 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -1935,6 +1935,8 @@ void merge_reloc_roots(struct reloc_control *rc) root->reloc_root = NULL; btrfs_put_root(reloc_root); } + clear_bit(BTRFS_ROOT_DEAD_RELOC_TREE, + &root->state); btrfs_put_root(root); } -- GitLab