Additional info:
reporter:       libreport-2.2.3
WARNING: CPU: 0 PID: 1725 at fs/block_dev.c:67 bdev_inode_switch_bdi+0x87/0x90()
Modules linked in: fuse uas usb_storage bnep bluetooth cfg80211 rfkill ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ebtable_nat ebtable_broute bridge stp llc ebtable_filter ebtables ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_mangle ip6table_security ip6table_raw ip6table_filter ip6_tables iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_mangle iptable_security iptable_raw ppdev joydev snd_intel8x0 snd_ac97_codec ac97_bus serio_raw amd64_edac_mod i2c_amd756 edac_core snd_seq snd_seq_device edac_mce_amd parport_pc snd_pcm parport k8temp shpchp amd_rng snd_timer snd i2c_amd8111 soundcore nfsd auth_rpcgss nfs_acl lockd grace sunrpc binfmt_misc btrfs xor raid6_pq nouveau video mxm_wmi wmi i2c_algo_bit drm_kms_helper ttm aic79xx
drm ata_generic scsi_transport_spi pata_acpi tg3 ptp firewire_ohci pps_core firewire_core pata_amd crc_itu_t
CPU: 0 PID: 1725 Comm: sftp-server Not tainted 3.18.6-100.fc20.x86_64 #1
Hardware name: Sun Microsystems   W1100z/2100z/K85AE, BIOS R01-B5 S1 09/29/2006
0000000000000000 0000000005a65ba5 ffff880076fe7ca8 ffffffff81745892
0000000000000000 0000000000000000 ffff880076fe7ce8 ffffffff81094f91
0000000000000000 ffff88017baf84b8 ffff88017baf8430 ffffffff81c6c9a0
Call Trace:
[<ffffffff81745892>] dump_stack+0x46/0x58
[<ffffffff81094f91>] warn_slowpath_common+0x81/0xa0
[<ffffffff810950aa>] warn_slowpath_null+0x1a/0x20
[<ffffffff81240c17>] bdev_inode_switch_bdi+0x87/0x90
[<ffffffff81241834>] __blkdev_put+0x74/0x1a0
[<ffffffff812422d0>] blkdev_put+0x50/0x130
[<ffffffff8120b4a4>] kill_block_super+0x44/0x70
[<ffffffffa074bccb>] fuse_kill_sb_blk+0x4b/0x60 [fuse]
[<ffffffff8120b7c9>] deactivate_locked_super+0x49/0x60
[<ffffffff8120bd9e>] deactivate_super+0x4e/0x70
[<ffffffff812286e3>] cleanup_mnt+0x43/0x90
[<ffffffff81228782>] __cleanup_mnt+0x12/0x20
[<ffffffff810b1727>] task_work_run+0xa7/0xe0
[<ffffffff8109762b>] do_exit+0x2eb/0xa60
[<ffffffff811340e4>] ? __audit_syscall_entry+0xb4/0x110
[<ffffffff81021c9c>] ? do_audit_syscall_entry+0x6c/0x70
[<ffffffff81097e2f>] do_group_exit+0x3f/0xa0
[<ffffffff81097ea4>] SyS_exit_group+0x14/0x20
[<ffffffff8174cce9>] system_call_fastpath+0x12/0x17

Potential duplicate: bug 1167001