My root filesystem is on btrfs and it seems to be getting (re-)mounted as
readonly. Nothing shows up in journalctl, but dmesg has the following stack:
[ 380.711078] ------------[ cut here ]------------
[ 380.711109] WARNING: CPU: 2 PID: 5631 at ../fs/btrfs/super.c:259
__btrfs_abort_transaction+0x4b/0x110 [btrfs]()
[ 380.711111] BTRFS: Transaction aborted (error -17)
[ 380.711112] Modules linked in: ppp_deflate bsd_comp ppp_async crc_ccitt
ppp_generic slhc nls_utf8 isofs rfcomm ctr ccm fuse af_packet vboxpci(O)
vboxnetadp(O) vboxnetflt(O) vboxdrv(O) bnep sr_mod cdrom xfs libcrc32c qmi_wwan
cdc_wdm option usbnet uas mii usb_wwan ecb usb_storage usbserial btusb
bluetooth 6lowpan_iphc uvcvideo videobuf2_vmalloc videobuf2_memops
videobuf2_core v4l2_common videodev rtsx_pci_ms memstick arc4
snd_hda_codec_hdmi rtsx_pci_sdmmc mmc_core snd_hda_codec_realtek
snd_hda_codec_generic iTCO_wdt iTCO_vendor_support x86_pkg_temp_thermal
intel_powerclamp coretemp snd_hda_intel snd_hda_controller snd_hda_codec
snd_hwdep snd_pcm kvm_intel kvm crct10dif_pclmul crc32_pclmul
ghash_clmulni_intel aesni_intel aes_x86_64 lrw gf128mul iwlmvm thinkpad_acpi
mac80211 snd_timer glue_helper joydev
[ 380.711142] ablk_helper cryptd iwlwifi snd cfg80211 rtsx_pci rfkill ac
e1000e tpm_tis tpm mei_me ptp serio_raw mei i2c_i801 soundcore lpc_ich mfd_core
pps_core shpchp thermal pcspkr intel_smartconnect battery processor wmi dm_mod
hid_logitech_dj btrfs xor raid6_pq crc32c_intel i915 xhci_hcd i2c_algo_bit
drm_kms_helper drm video button sg
[ 380.711161] CPU: 2 PID: 5631 Comm: snapperd Tainted: G O
3.16.7-29-desktop #1
[ 380.711162] Hardware name: LENOVO 20ARS16H00/20ARS16H00, BIOS GJET84WW (2.34
) 06/22/2015
[ 380.711164] 0000000000000009 ffffffff8161c923 ffff88016204ba88
ffffffff8105caf7
[ 380.711166] 00000000ffffffef ffff88016204bad8 ffff88020f8de8e0
ffffffffa02bb090
[ 380.711168] 0000000000000513 ffffffff8105cb5c ffffffffa02bf350
ffffffff00000020
[ 380.711171] Call Trace:
[ 380.711182] [<ffffffff810051ee>] dump_trace+0x8e/0x350
[ 380.711185] [<ffffffff81005556>] show_stack_log_lvl+0xa6/0x190
[ 380.711189] [<ffffffff81006c51>] show_stack+0x21/0x50
[ 380.711193] [<ffffffff8161c923>] dump_stack+0x49/0x6a
[ 380.711198] [<ffffffff8105caf7>] warn_slowpath_common+0x77/0x90
[ 380.711201] [<ffffffff8105cb5c>] warn_slowpath_fmt+0x4c/0x50
[ 380.711209] [<ffffffffa02140cb>] __btrfs_abort_transaction+0x4b/0x110
[btrfs]
[ 380.711230] [<ffffffffa0240848>] create_pending_snapshot+0x578/0x960
[btrfs]
[ 380.711271] [<ffffffffa0240cb9>] create_pending_snapshots+0x89/0xb0 [btrfs]
[ 380.711307] [<ffffffffa0242b3c>]
btrfs_commit_transaction.part.21+0x3ec/0x9f0 [btrfs]
[ 380.711351] [<ffffffffa02759d3>] btrfs_mksubvol.isra.29+0x553/0x5a0 [btrfs]
[ 380.711418] [<ffffffffa0275bb1>]
btrfs_ioctl_snap_create_transid+0x191/0x1a0 [btrfs]
[ 380.711482] [<ffffffffa0275d21>] btrfs_ioctl_snap_create_v2+0xf1/0x160
[btrfs]
[ 380.711546] [<ffffffffa0277def>] btrfs_ioctl+0xcaf/0x2b20 [btrfs]
[ 380.711603] [<ffffffff811cade7>] do_vfs_ioctl+0x2e7/0x4c0
[ 380.711611] [<ffffffff811cb041>] SyS_ioctl+0x81/0xa0
[ 380.711615] [<ffffffff8162360d>] system_call_fastpath+0x1a/0x1f
[ 380.711620] [<00007facb74cac27>] 0x7facb74cac26
[ 380.711622] ---[ end trace c172e2fe916ca5c1 ]---
[ 380.711624] BTRFS: error (device sdb1) in create_pending_snapshot:1299:
errno=-17 Object already exists
[ 380.711626] BTRFS info (device sdb1): forced readonly
[ 380.711628] BTRFS warning (device sdb1): Skipping commit of aborted
transaction.
[ 380.711630] BTRFS: error (device sdb1) in cleanup_transaction:1577:
errno=-17 Object already exists
[ 380.711869] systemd-journald[398]: Failed to truncate file to its own size:
Read-only file system
[ 380.711898] systemd-journald[398]: Failed to truncate file to its own size:
Read-only file system
# uname -a
Linux srinidhi.blr.novell.com 3.16.7-29-desktop #1 SMP PREEMPT Fri Oct 23
00:46:04 UTC 2015 (6be6a97) x86_64 x86_64 x86_64 GNU/Linux