Description of problem:
fs/buffer.c:3328
Sas copying data from backup disk to newly created ext4, on a 2 disk software raid1.
Memory was obviously being used as cache.

Additional info:
reporter:       libreport-2.7.2
kernel BUG at fs/buffer.c:3328!
invalid opcode: 0000 [#1] SMP
Modules linked in: uas usb_storage xfs libcrc32c btrfs xor raid6_pq fuse ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 xt_conntrack ip_set nfnetlink ebtable_nat ebtable_broute bridge ip6table_raw ip6table_nat nf_conntrack_ipv6 nf_defrag_ipv6 nf_nat_ipv6 ip6table_security ip6table_mangle iptable_raw iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_security iptable_mangle ebtable_filter ebtables ip6table_filter ip6_tables vfat fat ppdev kvm_amd kvm irqbypass crct10dif_pclmul crc32_pclmul ghash_clmulni_intel joydev snd_hda_codec_realtek snd_hda_codec_generic raid1 snd_hda_codec_hdmi snd_hda_intel sp5100_tco k10temp fam15h_power snd_hda_codec i2c_piix4 snd_hda_core snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd parport_pc soundcore shpchp parport acpi_cpufreq
 tpm_tis video tpm nfsd auth_rpcgss nfs_acl lockd grace sunrpc amdkfd amd_iommu_v2 radeon crc32c_intel serio_raw i2c_algo_bit drm_kms_helper 8021q garp stp ttm llc mrp r8169 drm mii fjes
CPU: 3 PID: 57 Comm: kswapd0 Not tainted 4.7.2-201.fc24.x86_64 #1
Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./F2A88XM-HD3P, BIOS F2 12/24/2015
task: ffff88042bc71e80 ti: ffff88042c34c000 task.ti: ffff88042c34c000
RIP: 0010:[<ffffffff8127d1a9>]  [<ffffffff8127d1a9>] free_buffer_head+0x49/0x50
RSP: 0018:ffff88042c34f9d0  EFLAGS: 00010287
RAX: ffff884200959ce0 RBX: ffff880200959c98 RCX: 0000000000000000
RDX: ffff880200959ce0 RSI: ffff88042c34f9d8 RDI: ffff880200959c98
RBP: ffff88042c34fa00 R08: ffffea00051ebe60 R09: ffff8803bd1b54d0
R10: 0000000000000238 R11: 0000000000000003 R12: 0000000000000001
R13: ffff8803bd1b54d0 R14: ffff88040b9a6000 R15: ffff88040b9a6398
FS:  0000000000000000(0000) GS:ffff88043ed80000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f07260bf000 CR3: 00000003affdd000 CR4: 00000000000406e0
Stack:
 ffffffff8127e2ed ffff880200959c98 000000001a7847b3 ffff880200959c98
 ffff880200959c98 ffffea00051ebe40 ffff88042c34fa48 ffffffff8132828b
 ffff88042c34fa88 ffffffff811fc30b ffffea00051ebe40 ffffea00051ebe40
Call Trace:
 [<ffffffff8127e2ed>] ? try_to_free_buffers+0x8d/0xe0
 [<ffffffff8132828b>] jbd2_journal_try_to_free_buffers+0xfb/0x120
 [<ffffffff811fc30b>] ? page_referenced+0x8b/0x170
 [<ffffffff812d6fb2>] ext4_releasepage+0x52/0xb0
 [<ffffffff811b46c1>] try_to_release_page+0x41/0x50
 [<ffffffff811ce3fc>] shrink_page_list+0x8cc/0xa60
 [<ffffffff811cec90>] shrink_inactive_list+0x200/0x4f0
 [<ffffffff811cf8a8>] shrink_zone_memcg+0x578/0x730
 [<ffffffff811cfb40>] shrink_zone+0xe0/0x300
 [<ffffffff811d0da1>] kswapd+0x4c1/0x880
 [<ffffffff811d08e0>] ? mem_cgroup_shrink_node_zone+0x170/0x170
 [<ffffffff810bf4f8>] kthread+0xd8/0xf0
 [<ffffffff817eba7f>] ret_from_fork+0x1f/0x40
 [<ffffffff810bf420>] ? kthread_worker_fn+0x180/0x180
Code: 89 e5 e8 6b 2d fa ff 65 ff 0d 54 64 d9 7e b8 01 00 00 00 65 0f c1 05 4b 64 d9 7e 3d ff 0f 00 00 7f 02 5d c3 e8 f9 fa ff ff 5d c3 <0f> 0b 0f 1f 44 00 00 0f 1f 44 00 00 55 b8 00 10 00 00 48 29 f0 
RIP  [<ffffffff8127d1a9>] free_buffer_head+0x49/0x50
 RSP <ffff88042c34f9d0>