quoted

[  282.380849] ------------[ cut here ]------------
[  282.380865] WARNING: at fs/inode.c:1315 iput+0x20b/0x210()
[  282.380869] Hardware name: HP Compaq 2510p Notebook PC
[  282.380873] Modules linked in: ext2 loop kvm_intel kvm fuse scsi_wait_scan usb_storage tun i915 drm_kms_helper drm yenta_socket sdhci_pci sdhci snd_hda_codec_analog iwl4965 mmc_core i2c_algo_bit pcmcia_core thermal container ac button fan battery e1000e iwl_legacy mac80211 snd_hda_intel cfg80211 snd_hda_codec pcmcia_rsrc processor rfkill snd_hwdep
[  282.380932] Pid: 715, comm: btrfs-cleaner Not tainted 3.1.0-rc3-00203-gdbf2e46 #139
[  282.380936] Call Trace:
[  282.380947]  [<ffffffff8103e7ba>] warn_slowpath_common+0x7a/0xb0
[  282.380954]  [<ffffffff8103e805>] warn_slowpath_null+0x15/0x20
[  282.380960]  [<ffffffff810eafbb>] iput+0x20b/0x210
[  282.380967]  [<ffffffff811b990b>] btrfs_iget+0x1eb/0x4a0
[  282.380975]  [<ffffffff811c3ce6>] btrfs_run_defrag_inodes+0x136/0x210
[  282.380982]  [<ffffffff811ad76f>] cleaner_kthread+0x17f/0x1a0
[  282.380988]  [<ffffffff81035b7d>] ? sub_preempt_count+0x9d/0xd0
[  282.380994]  [<ffffffff811ad5f0>] ? transaction_kthread+0x280/0x280
[  282.381001]  [<ffffffff8105b056>] kthread+0x96/0xa0
[  282.381027]  [<ffffffff81433914>] kernel_thread_helper+0x4/0x10
[  282.381034]  [<ffffffff8105afc0>] ? kthread_worker_fn+0x190/0x190
[  282.381039]  [<ffffffff81433910>] ? gs_change+0xb/0xb
[  282.381044] ---[ end trace 40720e359a3c0fea ]---

Konstantin's patch

    [PATCH] btrfs: fix warning in iput for bad-inode

fixed the issue.

Actually, not quite. Busy spin popped up as described in:

    http://www.spinics.net/lists/linux-btrfs/msg12156.html

-- 

  Sergei