From: Bartosz Chronowski During block group relocation, btrfs_relocate_block_group() is called to relocate a block group. It first makes the block group read-only by calling btrfs_inc_block_group_ro(). If there are pending space reservations or pinned extents in the current transaction, making the block group read-only can fail, leading to a transaction abort and a warning in cleanup_transaction() during the transaction commit in prepare_to_relocate(). To fix this, commit the current transaction before calling btrfs_inc_block_group_ro() in btrfs_relocate_block_group(). This drains the current transaction before the block group becomes read-only, ensuring that pending extents are unpinned and space reservations are committed. This does not claim global settlement of every reservation or later transaction, but it provides a clean state for marking the block group read-only. The setup commit in prepare_to_relocate() remains necessary because it commits the transaction started during the relocation setup (such as creating the reloc tree) to ensure everything is in a consistent state before starting to move extents. WARNING: fs/btrfs/transaction.c:2068 at cleanup_transaction+0x727/0x7c0 Call Trace: btrfs_commit_transaction+0x262c/0x30b0 fs/btrfs/transaction.c:2664 prepare_to_relocate+0x3dd/0x4e0 fs/btrfs/relocation.c:3541 relocate_block_group+0x141/0xe90 fs/btrfs/relocation.c:3566 do_nonremap_reloc+0xa7/0x560 fs/btrfs/relocation.c:5323 btrfs_relocate_block_group+0x6e2/0xaf0 fs/btrfs/relocation.c:5490 btrfs_relocate_chunk+0x114/0x830 fs/btrfs/volumes.c:3647 __btrfs_balance+0x1b6e/0x29e0 fs/btrfs/volumes.c:4586 btrfs_balance+0xaa6/0x1180 fs/btrfs/volumes.c:4973 btrfs_ioctl_balance+0x3dd/0x640 fs/btrfs/ioctl.c:3474 Fixes: 3fd0a5585eb9 ("Btrfs: Metadata ENOSPC handling for balance") Assisted-by: Gemini:gemini-3.5-flash Gemini:gemini-3.1-pro-preview syzbot Reported-by: syzbot+021d10c4d4edc87daa03@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=021d10c4d4edc87daa03 Link: https://syzkaller.appspot.com/ai_job?id=ca6bd6c4-fbcf-4533-af07-79b4a0eba74d Signed-off-by: Bartosz Chronowski --- diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c index fb85bc8b3..05f5110c2 100644 --- a/fs/btrfs/relocation.c +++ b/fs/btrfs/relocation.c @@ -5430,6 +5430,10 @@ int btrfs_relocate_block_group(struct btrfs_fs_info *fs_info, u64 group_start, if (ret < 0) goto out_put_rc; + ret = btrfs_commit_current_transaction(extent_root); + if (ret) + goto out; + ret = btrfs_inc_block_group_ro(rc->block_group, true); if (ret) goto out; base-commit: 8cdeaa50eae8dad34885515f62559ee83e7e8dda -- See https://goo.gle/syzbot-ai-patches for information about AI-generated patches. You can comment on the patch as usual, syzbot will try to address the comments and send a new version of the patch if necessary. syzbot engineers can be reached at syzkaller@googlegroups.com.