Description of problem:

Running kernel-3.8.0-0.rc5.git1.2.fc19.x86_64 with encfs in a btrfs filesystem, receive:

[ 3605.890250] ------------[ cut here ]------------
[ 3605.890283] WARNING: at fs/btrfs/extent_io.c:4718 map_private_extent_buffer+0xd4/0xe0 [btrfs]()
[ 3605.890285] Hardware name: C2SEA
[ 3605.890288] btrfs bad mapping eb start 510210048 len 4096, wanted 4096 8
[ 3605.890290] Modules linked in: fuse rfcomm bnep ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ip6table_filter nf_conntrack ip6_tables w83627ehf hwmon_vid snd_hda_codec_realtek snd_hda_intel snd_hda_codec uvcvideo snd_hwdep snd_seq snd_seq_device videobuf2_vmalloc btusb videobuf2_memops videobuf2_core videodev snd_pcm bluetooth media snd_page_alloc snd_timer snd coretemp iTCO_wdt iTCO_vendor_support i2c_i801 soundcore lpc_ich rfkill r8169 microcode mii mfd_core vhost_net tun macvtap macvlan kvm_intel kvm binfmt_misc uinput i2c_dev ata_generic pata_acpi btrfs zlib_deflate libcrc32c i915 firewire_ohci firewire_core video i2c_algo_bit drm_kms_helper crc_itu_t drm pata_it8213 i2c_core
[ 3605.890335] Pid: 1962, comm: encfs Not tainted 3.8.0-0.rc5.git1.2.fc19.x86_64 #1
[ 3605.890337] Call Trace:
[ 3605.890355]  [<ffffffffa01a1b00>] ? map_private_extent_buffer+0x30/0xe0 [btrfs]
[ 3605.890362]  [<ffffffff8105c1f0>] warn_slowpath_common+0x70/0xa0
[ 3605.890365]  [<ffffffff8105c26c>] warn_slowpath_fmt+0x4c/0x50
[ 3605.890382]  [<ffffffffa01a1ba4>] map_private_extent_buffer+0xd4/0xe0 [btrfs]
[ 3605.890399]  [<ffffffffa0197970>] btrfs_set_token_64+0x60/0xf0 [btrfs]
[ 3605.890416]  [<ffffffffa01b9944>] btrfs_log_changed_extents+0x384/0x600 [btrfs]
[ 3605.890433]  [<ffffffffa01ba4f8>] btrfs_log_inode+0x3b8/0x660 [btrfs]
[ 3605.890450]  [<ffffffffa01bb459>] btrfs_log_inode_parent+0x169/0x450 [btrfs]
[ 3605.890466]  [<ffffffffa01bb77a>] btrfs_log_dentry_safe+0x3a/0x60 [btrfs]
[ 3605.890482]  [<ffffffffa01923c0>] btrfs_sync_file+0x150/0x1f0 [btrfs]
[ 3605.890487]  [<ffffffff811c44b6>] do_fsync+0x56/0x80
[ 3605.890490]  [<ffffffff811c4740>] sys_fsync+0x10/0x20
[ 3605.890494]  [<ffffffff8163ce59>] system_call_fastpath+0x16/0x1b
[ 3605.890496] ---[ end trace 7e5e84fc43a629f8 ]---
[ 3605.890504] BUG: unable to handle kernel NULL pointer dereference at           (null)
[ 3605.890552] IP: [<ffffffffa01a1da3>] write_extent_buffer+0xd3/0x150 [btrfs]
[ 3605.890604] PGD 1f2796067 PUD 1f2797067 PMD 0 
[ 3605.890638] Oops: 0000 [#1] SMP 
[ 3605.890662] Modules linked in: fuse rfcomm bnep ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack ip6table_filter nf_conntrack ip6_tables w83627ehf hwmon_vid snd_hda_codec_realtek snd_hda_intel snd_hda_codec uvcvideo snd_hwdep snd_seq snd_seq_device videobuf2_vmalloc btusb videobuf2_memops videobuf2_core videodev snd_pcm bluetooth media snd_page_alloc snd_timer snd coretemp iTCO_wdt iTCO_vendor_support i2c_i801 soundcore lpc_ich rfkill r8169 microcode mii mfd_core vhost_net tun macvtap macvlan kvm_intel kvm binfmt_misc uinput i2c_dev ata_generic pata_acpi btrfs zlib_deflate libcrc32c i915 firewire_ohci firewire_core video i2c_algo_bit drm_kms_helper crc_itu_t drm pata_it8213 i2c_core
[ 3605.891143] CPU 1 
[ 3605.891157] Pid: 1962, comm: encfs Tainted: G        W    3.8.0-0.rc5.git1.2.fc19.x86_64 #1 Supermicro C2SEA/C2SEA
[ 3605.891197] RIP: 0010:[<ffffffffa01a1da3>]  [<ffffffffa01a1da3>] write_extent_buffer+0xd3/0x150 [btrfs]
[ 3605.891197] RSP: 0018:ffff8801f27abc20  EFLAGS: 00010202
[ 3605.891197] RAX: 0000000000000000 RBX: 0000000000000008 RCX: 0000000000000008
[ 3605.891197] RDX: 0000000000001008 RSI: 000000001e694000 RDI: ffff880107078810
[ 3605.891197] RBP: ffff8801f27abc50 R08: 000000000000000a R09: 0000000000000399
[ 3605.891197] R10: 0000000000000000 R11: ffff8801f27ab8d6 R12: ffff8801f27abc80
[ 3605.891197] R13: ffff880107078810 R14: 0000000000000000 R15: 0000000000000008
[ 3605.891197] FS:  00007f441fb63800(0000) GS:ffff880237c80000(0000) knlGS:0000000000000000
[ 3605.891197] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 3605.891197] CR2: 0000000000000000 CR3: 000000020265c000 CR4: 00000000000007e0
[ 3605.891197] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 3605.891197] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 3605.891197] Process encfs (pid: 1962, threadinfo ffff8801f27aa000, task ffff8801f260dd80)
[ 3605.891197] Stack:
[ 3605.891197]  0000000000001000 ffff8801f27abd70 ffff880107078810 0000000000001000
[ 3605.891197]  0000000000000025 0000000000000fdb ffff8801f27abcb0 ffffffffa01979f0
[ 3605.891197]  0000000000000000 ffff8801e0166000 0000000000001000 0000000000001000
[ 3605.891197] Call Trace:
[ 3605.891197]  [<ffffffffa01979f0>] btrfs_set_token_64+0xe0/0xf0 [btrfs]
[ 3605.891197]  [<ffffffffa01b9944>] btrfs_log_changed_extents+0x384/0x600 [btrfs]
[ 3605.891197]  [<ffffffffa01ba4f8>] btrfs_log_inode+0x3b8/0x660 [btrfs]
[ 3605.891197]  [<ffffffffa01bb459>] btrfs_log_inode_parent+0x169/0x450 [btrfs]
[ 3605.891197]  [<ffffffffa01bb77a>] btrfs_log_dentry_safe+0x3a/0x60 [btrfs]
[ 3605.891197]  [<ffffffffa01923c0>] btrfs_sync_file+0x150/0x1f0 [btrfs]
[ 3605.891197]  [<ffffffff811c44b6>] do_fsync+0x56/0x80
[ 3605.891197]  [<ffffffff811c4740>] sys_fsync+0x10/0x20
[ 3605.891197]  [<ffffffff8163ce59>] system_call_fastpath+0x16/0x1b
[ 3605.891197] Code: e0 0c 48 01 d0 4c 89 c2 4a 8d 3c 30 e8 37 2d 15 e1 4c 8b 45 d0 4d 01 c4 4d 29 c7 74 3b 45 31 f6 49 8b 85 50 01 00 00 48 8b 04 18 <48> 8b 30 83 e6 08 75 95 be af 12 00 00 48 c7 c7 a4 cb 1e a0 48 
[ 3605.891197] RIP  [<ffffffffa01a1da3>] write_extent_buffer+0xd3/0x150 [btrfs]
[ 3605.891197]  RSP <ffff8801f27abc20>
[ 3605.891197] CR2: 0000000000000000
[ 3605.905108] ---[ end trace 7e5e84fc43a629f9 ]---

Version-Release number of selected component (if applicable):

kernel-3.8.0-0.rc5.git1.2.fc19.x86_64

How reproducible:

Always

Steps to Reproduce:
1.Boot kernel-3.8.0-0.rc5.git1.2.fc19.x86_64
2.Mount and use encfs files
3.Wait
  
Actual results:

Bug occurs within a few minutes.

Expected results:

No bug

Additional info: The btrfs filesystem has to be mounted '-o recovery' after rebooting.