I have expansion issue with 5.1 - 5022 update too. My hardware : Motherboard ASRock E350M1, 2GB RAM, 1x WD RED 2TB, 1x WD RED 3TB, 2x WD RE4 500GB. Volume starts expanding in web interface and crashs after few seconds.
I tried to scrub volume - wihout problems:
[ 343.244147] md: requested-resync of RAID array md2
[ 343.244153] md: minimum _guaranteed_ speed: 10000 KB/sec/disk.
[ 343.244157] md: using maximum available idle IO bandwidth (but not more than 200000 KB/sec) for requested-resync.
[ 343.244165] md: using 128k window, over a total of 483555264k.
[ 5726.692886] md: md2: requested-resync done.
And expand volme after that:
[ 7245.250107] Adding 511996k swap on /swap. Priority:-2 extents:5 across:602108k
[ 7245.344014] BUG: unable to handle kernel NULL pointer dereference at 0000000000000028
[ 7245.344027] IP: [] add_new_gdb+0x25/0x470
[ 7245.344040] PGD 6047e067 PUD 604f3067 PMD 0
[ 7245.344046] Oops: 0000 [#2] SMP
[ 7245.344051] CPU 0
[ 7245.344053] Modules linked in: cifs udf isofs loop usbhid hid usblp usb_storage bromolow_synobios(P) adt7475 i2c_i801 btrfs synoacl_vfs(P) zlib_deflate hfsplus md4 hmac tn40xx(O) i2c_algo_bit fuse vfat fat chainiv cpufreq_conservative cpufreq_powersave cpufreq_performance cpufreq_ondemand mperf processor cpufreq_stats freq_table dm_snapshot crc_itu_t quota_v2 quota_tree psnap p8022 llc sit tunnel4 zram(C) etxhci_hcd xhci_hcd ehci_hcd uhci_hcd ohci_hcd usbcore usb_common mvsas arcmsr megaraid_sas megaraid_mbox megaraid_mm mpt2sas mptsas mptspi mptscsih mptbase scsi_transport_spi scsi_wait_scan sg ata_piix sata_uli sata_svw sata_qstor sata_sis pata_sis stex sata_sx4 sata_promise sata_nv sata_via sata_sil pdc_adma iscsi_tcp libiscsi_tcp libiscsi enic qlge qlcnic qla3xxx netxen_nic cnic ipv6 bnx2x be2net sis900 sis190 atl1e(O) atl1c atl2(O) atl1(O) alx(O) sky2 skge via_velocity crc_ccitt via_rhine r8101 r8168 r8169 8139too 8139cp tg3 broadcom libphy bnx2 ssb(O) uio forcedeth ixgbe ixgb igb ioatdma e1000e e1000 e100 dca pcnet32 amd8111e mdio mii container thermal_sys compat(O) cryptd ecryptfs sha512_generic sha256_generic sha1_generic ecb aes_x86_64 authenc des_generic libcrc32c crc32c eseqiv krng ansi_cprng cts rng aes_generic md5 cbc cryptomgr pcompress aead crypto_hash crypto_blkcipher crypto_wq crypto_algapi [last unloaded: i2c_i801]
[ 7245.344197]
[ 7245.344202] Pid: 30747, comm: resize2fs Tainted: P D C O 3.2.40 #7 To Be Filled By O.E.M. Synoden/E350M1
[ 7245.344209] RIP: 0010:[] [] add_new_gdb+0x25/0x470
[ 7245.344217] RSP: 0018:ffff880060647b58 EFLAGS: 00010282
[ 7245.344221] RAX: 0000000000000074 RBX: 0000000000001d10 RCX: ffff88006b91f000
[ 7245.344225] RDX: 0000000000001d00 RSI: 0000000000000000 RDI: ffff88005ceae360
[ 7245.344229] RBP: ffff880060647be8 R08: 7010000000000000 R09: 0000000000000000
[ 7245.344233] R10: ffde9f3da028ce02 R11: ffff880061131130 R12: ffff88006b91f000
[ 7245.344236] R13: 0000000000001d00 R14: 0000000000000000 R15: 0000000000000000
[ 7245.344241] FS: 00000000006fc880(0063) GS:ffff88006fa00000(0000) knlGS:00000000f6f446d0
[ 7245.344246] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 7245.344249] CR2: 0000000000000028 CR3: 000000004146e000 CR4: 00000000000006f0
[ 7245.344253] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 7245.344257] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 7245.344261] Process resize2fs (pid: 30747, threadinfo ffff880060646000, task ffff88006e54e6a0)
[ 7245.344265] Stack:
[ 7245.344267] ffff88006a2c0800 ffff8800610ceeb8 ffff88005ceae360 ffffffff8161b590
[ 7245.344274] ffff8800610ceeb8 0000000000000000 ffff880060647ba8 ffffffff8119ff86
[ 7245.344280] ffff88005ceae360 ffff88000360c338 ffff880060647be8 ffffffff81185b98
[ 7245.344287] Call Trace:
[ 7245.344296] [] ? jbd2_journal_get_write_access+0x36/0x50
[ 7245.344302] [] ? __ext4_journal_get_write_access+0x38/0x80
[ 7245.344308] [] ext4_flex_group_add+0x57e/0xd00
[ 7245.344314] [] ext4_resize_fs+0x662/0x8f0
[ 7245.344321] [] ? do_last+0x538/0xaa0
[ 7245.344327] [] ? __mnt_want_write+0x30/0x50
[ 7245.344334] [] ext4_ioctl+0x290/0xaa0
[ 7245.344340] [] do_vfs_ioctl+0xb4/0x8b0
[ 7245.344346] [] ? putname+0x2e/0x40
[ 7245.344351] [] ? do_sys_open+0x164/0x1d0
[ 7245.344357] [] sys_ioctl+0x99/0xa0
[ 7245.344364] [] system_call_fastpath+0x16/0x1b
[ 7245.344367] Code: 84 00 00 00 00 00 55 48 89 e5 48 81 ec 90 00 00 00 4c 89 6d e8 4c 89 75 f0 41 89 d5 48 89 5d d8 4c 89 65 e0 49 89 f6 4c 89 7d f8 <4c> 8b 7e 28 48 89 7d 88 49 8b 8f 40 03 00 00 48 8b 41 68 48 89
[ 7245.344418] RIP [] add_new_gdb+0x25/0x470
[ 7245.344423] RSP
[ 7245.344426] CR2: 0000000000000028
[ 7245.344432] ---[ end trace 8022fe148d921fe4 ]---