freetz

Hi everyone, although I'm not using XPEnology but rather a stock DS218 with DSM 7.1, I'm asking this question here because a vaguely similar question has been asked and answered really competently here before. The situation with me is different in the sense that the cause of the error can be traced back to the creation of a snapshot for a specific shared folder (/volume1/homes). This snapshot has been created for years every hour, but a few days ago the creation resulted in this problem (no reboot or any other noticeable problem occurred during the hour between the last working snapshot and the one that triggered the problem): The rest of the system is running perfectly fine, so once I disable the snapshot for this specific folder, no error messages occur and a 19 hour extended S.M.A.R.T. test returns no failures on both disks. I haven't done data scrubbing ever so far, but have done it now which also completes without any warnings. But as soon as I execute either a planned or manual snapshot of /volume/homes, the system immediately goes into write-protected mode and system status turns to critical. I can then reboot, set the system to read-write again, reboot again and everything is fine again with no errors for days. I have also written a tar file of /volume/homes on the same disc in order to have another backup and then moved it to external storage. No error occurred during the creation of this archive. This is the output of /var/log/messages once the error occurs: 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.141294] ------------[ cut here ]------------ 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.146508] WARNING: CPU: 0 PID: 8593 at fs/btrfs/extent-tree.c:1666 lookup_inline_extent_backref+0x5a5/0x5f0 [btrfs]() 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.158574] Modules linked in: pci_stub vfio_pci vfio_virqfd vfio_iommu_type1 vfio vhost_net(O) kvm_intel kvm irqbypass nfnetlink tun xt_ipvs ip_vs_rr ip_vs xt_mark br_netfilter bridge stp cmac aufs macvlan veth ctr ccm xt_conntrack xt_addrtype ipt_MASQUERADE xt_REDIRECT nf_nat_masquerade_ipv4 xt_nat nf_nat_redirect xt_policy xfrm6_mode_transport xfrm4_mode_transport xfrm6_mode_tunnel xfrm4_mode_tunnel xfrm6_mode_beet xfrm4_mode_beet deflate authencesn ipcomp6 exfat(O) ipcomp xfrm6_tunnel xfrm4_tunnel fuse tunnel6 esp6 esp4 ah6 ah4 xfrm_ipcomp af_key xfrm_user xfrm_algo l2tp_ppp l2tp_core ppp_deflate bsd_comp ppp_mppe echainiv xt_TCPMSS iptable_mangle pppox ppp_async ppp_generic slhc 8021q vhost_scsi(O) vhost(O) tcm_loop(O) iscsi_target_mod(O) target_core_user(O) target_core_ep(O) target_core_multi_file(O) 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.238862] target_core_file(O) target_core_iblock(O) target_core_mod(O) syno_extent_pool(PO) rodsp_ep(O) ch341(OE) cp210x(OE) cdc_acm ftdi_sio usbserial udf isofs cifs synoacl_vfs(PO) iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv6 ip6table_filter ip6_tables xt_recent xt_iprange xt_limit xt_state xt_tcpudp xt_multiport xt_LOG nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables x_tables nfsd btrfs ecryptfs zstd_decompress zstd_compress xxhash xor raid6_pq lockd grace rpcsec_gss_krb5 auth_rpcgss sunrpc leds_lp3943 aesni_intel glue_helper lrw gf128mul ablk_helper syno_hddmon(P) apollolake_synobios(PO) hid_generic usbhid hid usblp i915 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cfbfillrect cfbcopyarea cfbimgblt drm drm_panel_orientation_quirks iosf_mbi fb fbdev video backlight 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.316868] button uhci_hcd ehci_pci ehci_hcd usb_storage r8168(O) i2c_algo_bit igb(O) e1000e(O) sg dm_snapshot dm_bufio crc_itu_t crc_ccitt psnap p8022 llc hfsplus md4 hmac sit tunnel4 openvswitch flashcache_syno(O) gre flashcache(O) syno_flashcache_control(O) nf_defrag_ipv6 ipv6 nf_conntrack dm_mod arc4 crc32c_intel cryptd ecb aes_x86_64 authenc des_generic ansi_cprng cts md5 cbc cpufreq_powersave cpufreq_performance acpi_cpufreq processor cpufreq_stats vxlan ip6_udp_tunnel udp_tunnel ip_tunnel loop sha256_generic synorbd(PO) synofsbd(PO) etxhci_hcd xhci_pci xhci_hcd usbcore usb_common [last unloaded: apollolake_synobios] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.377684] CPU: 0 PID: 8593 Comm: synosharesnapsh Tainted: P OE 4.4.180+ #42962 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.387110] Hardware name: Synology DS218+/DS218+, BIOS M.135 11/11/2019 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.394593] 0000000000000000 ffff8802a5b478d0 ffffffff812f2dbd 0000000000000009 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.402868] 0000000000000000 ffff8802a5b47908 ffffffff81051703 ffff8804677c8770 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.411140] 0000000000000000 0000000000002000 0000040af9d6d000 ffff8804599d7bd0 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.419414] Call Trace: 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.422145] [<ffffffff812f2dbd>] dump_stack+0x4d/0x70 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.427884] [<ffffffff81051703>] warn_slowpath_common+0x83/0xa0 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.434595] [<ffffffff810517d6>] warn_slowpath_null+0x16/0x20 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.441125] [<ffffffffa0799b45>] lookup_inline_extent_backref+0x5a5/0x5f0 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.449593] [<ffffffffa07b6004>] ? btrfs_mark_buffer_dirty+0x84/0xc0 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.457576] [<ffffffffa0799bea>] insert_inline_extent_backref+0x5a/0xe0 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.465849] [<ffffffffa0799ff7>] __btrfs_inc_extent_ref+0xe7/0x330 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.473640] [<ffffffffa079dfd6>] __btrfs_run_delayed_refs+0xd36/0x1900 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.481821] [<ffffffffa07a2569>] btrfs_run_delayed_refs_and_get_processed+0xc9/0x4d0 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.491356] [<ffffffffa07bdfdc>] btrfs_commit_transaction+0x15c/0xf70 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.499425] [<ffffffff811304e5>] ? find_get_pages_tag+0xc5/0x170 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.506245] [<ffffffffa07dadbe>] btrfs_sync_file+0x22e/0x360 [btrfs] 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.513439] [<ffffffff811c7f79>] vfs_fsync_range+0x49/0xa0 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.519658] [<ffffffff811c802b>] do_fsync+0x3b/0x70 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.525197] [<ffffffff811c829b>] SyS_fsync+0xb/0x10 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.530728] [<ffffffff8157f04a>] entry_SYSCALL_64_fastpath+0x1e/0x8e 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.537963] ---[ end trace 1080ee8b7ee410c1 ]--- 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.543138] ------------[ cut here ]------------ 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.548311] WARNING: CPU: 0 PID: 8593 at fs/btrfs/extent-tree.c:3489 btrfs_run_delayed_refs_and_get_processed+0x4b3/0x4d0 [btrfs]() 2022-10-20T20:41:02+02:00 DS218 kernel: [84500.561555] Modules linked in: pci_stub vfio_pci vfio_virqfd vfio_iommu_type1 vfio vhost_net(O) kvm_intel kvm irqbypass nfnetlink tun xt_ipvs ip_vs_rr ip_vs xt_mark br_netfilter bridge stp cmac aufs macvlan veth ctr ccm xt_conntrack xt_addrtype ipt_MASQUERADE xt_REDIRECT nf_nat_masquerade_ipv4 xt_nat nf_nat_redirect xt_policy xfrm6_mode_transport xfrm4_mode_transport xfrm6_mode_tunnel xfrm4_mode_tunnel xfrm6_mode_beet xfrm4_mode_beet deflate authencesn ipcomp6 exfat(O) ipcomp xfrm6_tunnel xfrm4_tunnel fuse tunnel6 esp6 esp4 ah6 ah4 xfrm_ipcomp af_key xfrm_user xfrm_algo l2tp_ppp l2tp_core ppp_deflate bsd_comp ppp_mppe echainiv xt_TCPMSS iptable_mangle pppox ppp_async ppp_generic slhc 8021q vhost_scsi(O) vhost(O) tcm_loop(O) iscsi_target_mod(O) target_core_user(O) target_core_ep(O) target_core_multi_file(O) 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.641627] target_core_file(O) target_core_iblock(O) target_core_mod(O) syno_extent_pool(PO) rodsp_ep(O) ch341(OE) cp210x(OE) cdc_acm ftdi_sio usbserial udf isofs cifs synoacl_vfs(PO) iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv6 ip6table_filter ip6_tables xt_recent xt_iprange xt_limit xt_state xt_tcpudp xt_multiport xt_LOG nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables x_tables nfsd btrfs ecryptfs zstd_decompress zstd_compress xxhash xor raid6_pq lockd grace rpcsec_gss_krb5 auth_rpcgss sunrpc leds_lp3943 aesni_intel glue_helper lrw gf128mul ablk_helper syno_hddmon(P) apollolake_synobios(PO) hid_generic usbhid hid usblp i915 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cfbfillrect cfbcopyarea cfbimgblt drm drm_panel_orientation_quirks iosf_mbi fb fbdev video backlight 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.719447] button uhci_hcd ehci_pci ehci_hcd usb_storage r8168(O) i2c_algo_bit igb(O) e1000e(O) sg dm_snapshot dm_bufio crc_itu_t crc_ccitt psnap p8022 llc hfsplus md4 hmac sit tunnel4 openvswitch flashcache_syno(O) gre flashcache(O) syno_flashcache_control(O) nf_defrag_ipv6 ipv6 nf_conntrack dm_mod arc4 crc32c_intel cryptd ecb aes_x86_64 authenc des_generic ansi_cprng cts md5 cbc cpufreq_powersave cpufreq_performance acpi_cpufreq processor cpufreq_stats vxlan ip6_udp_tunnel udp_tunnel ip_tunnel loop sha256_generic synorbd(PO) synofsbd(PO) etxhci_hcd xhci_pci xhci_hcd usbcore usb_common [last unloaded: apollolake_synobios] 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.780111] CPU: 0 PID: 8593 Comm: synosharesnapsh Tainted: P W OE 4.4.180+ #42962 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.789537] Hardware name: Synology DS218+/DS218+, BIOS M.135 11/11/2019 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.797009] 0000000000000000 ffff8802a5b47b78 ffffffff812f2dbd 0000000000000009 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.805281] ffff8802a5b47bc0 ffff8802a5b47bb0 ffffffff81051703 ffffffffa086e617 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.813550] ffff8804599d7bd0 0000000000000200 ffff8804599d7bd0 ffff880459b66000 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.821818] Call Trace: 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.824543] [<ffffffff812f2dbd>] dump_stack+0x4d/0x70 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.830276] [<ffffffff81051703>] warn_slowpath_common+0x83/0xa0 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.836981] [<ffffffff81051769>] warn_slowpath_fmt+0x49/0x50 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.843409] [<ffffffffa079e7a1>] ? __btrfs_run_delayed_refs+0x1501/0x1900 [btrfs] 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.851875] [<ffffffffa07a2953>] btrfs_run_delayed_refs_and_get_processed+0x4b3/0x4d0 [btrfs] 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.861509] [<ffffffffa07bdfdc>] btrfs_commit_transaction+0x15c/0xf70 [btrfs] 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.869575] [<ffffffff811304e5>] ? find_get_pages_tag+0xc5/0x170 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.876392] [<ffffffffa07dadbe>] btrfs_sync_file+0x22e/0x360 [btrfs] 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.883586] [<ffffffff811c7f79>] vfs_fsync_range+0x49/0xa0 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.889805] [<ffffffff811c802b>] do_fsync+0x3b/0x70 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.895346] [<ffffffff811c829b>] SyS_fsync+0xb/0x10 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.900884] [<ffffffff8157f04a>] entry_SYSCALL_64_fastpath+0x1e/0x8e 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.908107] ---[ end trace 1080ee8b7ee410c2 ]--- 2022-10-20T20:41:03+02:00 DS218 kernel: [84500.913274] BTRFS: error (device dm-0) in btrfs_run_delayed_refs_and_get_processed:3489: errno=-5 IO failure 2022-10-20T20:41:03+02:00 DS218 root[8738]: Restart synosnmpcd to fix possible DB issue 2022-10-20T20:41:04+02:00 DS218 root[8852]: No alive volume. 2022-10-20T20:41:03+02:00 DS218 root[8738]: Restart synosnmpcd to fix possible DB issue 2022-10-20T20:41:04+02:00 DS218 root[8852]: No alive volume. 2022-10-20T20:41:04+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:82 Fail to setxattr on /volume1/@sharesnap/homes, name: user.snapcount, value: 21, strerror: Read-only file system 2022-10-20T20:41:04+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:183 Fail to set ShareSnapCount of [homes] to 21. 2022-10-20T20:41:04+02:00 DS218 synoretainer[8677]: snapshot_delete.c:210 Failed to decrease snapcount for share [homes] [0x0000 file_get_section.c:76] 2022-10-20T20:41:04+02:00 DS218 synoretainer[8677]: snapshot_delete.c:393 Failed to remove snapshots.[0x0000 file_get_section.c:76] 2022-10-20T20:41:06+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:82 Fail to setxattr on /volume1/@sharesnap/homes, name: user.snapcount, value: 21, strerror: Read-only file system 2022-10-20T20:41:06+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:183 Fail to set ShareSnapCount of [homes] to 21. 2022-10-20T20:41:06+02:00 DS218 synoretainer[8677]: snapshot_delete.c:210 Failed to decrease snapcount for share [homes] [0x0000 file_get_section.c:76] 2022-10-20T20:41:06+02:00 DS218 synoretainer[8677]: snapshot_delete.c:393 Failed to remove snapshots.[0x0000 file_get_section.c:76] 2022-10-20T20:41:09+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:82 Fail to setxattr on /volume1/@sharesnap/homes, name: user.snapcount, value: 21, strerror: Read-only file system 2022-10-20T20:41:09+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:183 Fail to set ShareSnapCount of [homes] to 21. 2022-10-20T20:41:09+02:00 DS218 synoretainer[8677]: snapshot_delete.c:210 Failed to decrease snapcount for share [homes] [0x0000 file_get_section.c:76] 2022-10-20T20:41:09+02:00 DS218 synoretainer[8677]: snapshot_delete.c:393 Failed to remove snapshots.[0x0000 file_get_section.c:76] 2022-10-20T20:41:10+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:82 Fail to setxattr on /volume1/@sharesnap/homes, name: user.snapcount, value: 21, strerror: Read-only file system 2022-10-20T20:41:10+02:00 DS218 synoretainer[8677]: snapshot_snapcount.c:183 Fail to set ShareSnapCount of [homes] to 21. 2022-10-20T20:41:10+02:00 DS218 synoretainer[8677]: snapshot_delete.c:210 Failed to decrease snapcount for share [homes] [0x0000 file_get_section.c:76] 2022-10-20T20:41:10+02:00 DS218 synoretainer[8677]: snapshot_delete.c:393 Failed to remove snapshots.[0x0000 file_get_section.c:76] 2022-10-20T20:41:10+02:00 DS218 synoretainer[8677]: retention_run_policy.c:618(SYNORETENTIONRunPolicyEx)[8677]: Failed to delete snapshot GMT+02-2022.10.14-23.00.01 of prefix = Share#, name = homes 2022-10-20T20:41:20+02:00 DS218 synovpnnet[9461]: connection.c:1145 Fail to delete entry from database: DELETE FROM synovpn_con_tb WHERE prtltype=3 2022-10-20T20:41:20+02:00 DS218 synovpnnet[9461]: connection.c:1206 Fail to delete entry from database 2022-10-20T20:41:20+02:00 DS218 synovpnnet[9461]: connection.c:918 SYNOVPNDBConnDeleteByPrtl(/var/packages/VPNCenter/target/var/log/synovpncon.db) failed 2022-10-20T20:41:20+02:00 DS218 synovpnnet[9461]: connection.c:952 failed to refresh openvpn connection DB and this is the output of dmesg at that time: [84500.141294] ------------[ cut here ]------------ [84500.146508] WARNING: CPU: 0 PID: 8593 at fs/btrfs/extent-tree.c:1666 lookup_inline_extent_backref+0x5a5/0x5f0 [btrfs]() [84500.158574] Modules linked in: pci_stub vfio_pci vfio_virqfd vfio_iommu_type1 vfio vhost_net(O) kvm_intel kvm irqbypass nfnetlink tun xt_ipvs ip_vs_rr ip_vs xt_mark br_netfilter bridge stp cmac aufs macvlan veth ctr ccm xt_conntrack xt_addrtype ipt_MASQUERADE xt_REDIRECT nf_nat_masquerade_ipv4 xt_nat nf_nat_redirect xt_policy xfrm6_mode_transport xfrm4_mode_transport xfrm6_mode_tunnel xfrm4_mode_tunnel xfrm6_mode_beet xfrm4_mode_beet deflate authencesn ipcomp6 exfat(O) ipcomp xfrm6_tunnel xfrm4_tunnel fuse tunnel6 esp6 esp4 ah6 ah4 xfrm_ipcomp af_key xfrm_user xfrm_algo l2tp_ppp l2tp_core ppp_deflate bsd_comp ppp_mppe echainiv xt_TCPMSS iptable_mangle pppox ppp_async ppp_generic slhc 8021q vhost_scsi(O) vhost(O) tcm_loop(O) iscsi_target_mod(O) target_core_user(O) target_core_ep(O) target_core_multi_file(O) [84500.238862] target_core_file(O) target_core_iblock(O) target_core_mod(O) syno_extent_pool(PO) rodsp_ep(O) ch341(OE) cp210x(OE) cdc_acm ftdi_sio usbserial udf isofs cifs synoacl_vfs(PO) iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv6 ip6table_filter ip6_tables xt_recent xt_iprange xt_limit xt_state xt_tcpudp xt_multiport xt_LOG nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables x_tables nfsd btrfs ecryptfs zstd_decompress zstd_compress xxhash xor raid6_pq lockd grace rpcsec_gss_krb5 auth_rpcgss sunrpc leds_lp3943 aesni_intel glue_helper lrw gf128mul ablk_helper syno_hddmon(P) apollolake_synobios(PO) hid_generic usbhid hid usblp i915 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cfbfillrect cfbcopyarea cfbimgblt drm drm_panel_orientation_quirks iosf_mbi fb fbdev video backlight [84500.316868] button uhci_hcd ehci_pci ehci_hcd usb_storage r8168(O) i2c_algo_bit igb(O) e1000e(O) sg dm_snapshot dm_bufio crc_itu_t crc_ccitt psnap p8022 llc hfsplus md4 hmac sit tunnel4 openvswitch flashcache_syno(O) gre flashcache(O) syno_flashcache_control(O) nf_defrag_ipv6 ipv6 nf_conntrack dm_mod arc4 crc32c_intel cryptd ecb aes_x86_64 authenc des_generic ansi_cprng cts md5 cbc cpufreq_powersave cpufreq_performance acpi_cpufreq processor cpufreq_stats vxlan ip6_udp_tunnel udp_tunnel ip_tunnel loop sha256_generic synorbd(PO) synofsbd(PO) etxhci_hcd xhci_pci xhci_hcd usbcore usb_common [last unloaded: apollolake_synobios] [84500.377684] CPU: 0 PID: 8593 Comm: synosharesnapsh Tainted: P OE 4.4.180+ #42962 [84500.387110] Hardware name: Synology DS218+/DS218+, BIOS M.135 11/11/2019 [84500.394593] 0000000000000000 ffff8802a5b478d0 ffffffff812f2dbd 0000000000000009 [84500.402868] 0000000000000000 ffff8802a5b47908 ffffffff81051703 ffff8804677c8770 [84500.411140] 0000000000000000 0000000000002000 0000040af9d6d000 ffff8804599d7bd0 [84500.419414] Call Trace: [84500.422145] [<ffffffff812f2dbd>] dump_stack+0x4d/0x70 [84500.427884] [<ffffffff81051703>] warn_slowpath_common+0x83/0xa0 [84500.434595] [<ffffffff810517d6>] warn_slowpath_null+0x16/0x20 [84500.441125] [<ffffffffa0799b45>] lookup_inline_extent_backref+0x5a5/0x5f0 [btrfs] [84500.449593] [<ffffffffa07b6004>] ? btrfs_mark_buffer_dirty+0x84/0xc0 [btrfs] [84500.457576] [<ffffffffa0799bea>] insert_inline_extent_backref+0x5a/0xe0 [btrfs] [84500.465849] [<ffffffffa0799ff7>] __btrfs_inc_extent_ref+0xe7/0x330 [btrfs] [84500.473640] [<ffffffffa079dfd6>] __btrfs_run_delayed_refs+0xd36/0x1900 [btrfs] [84500.481821] [<ffffffffa07a2569>] btrfs_run_delayed_refs_and_get_processed+0xc9/0x4d0 [btrfs] [84500.491356] [<ffffffffa07bdfdc>] btrfs_commit_transaction+0x15c/0xf70 [btrfs] [84500.499425] [<ffffffff811304e5>] ? find_get_pages_tag+0xc5/0x170 [84500.506245] [<ffffffffa07dadbe>] btrfs_sync_file+0x22e/0x360 [btrfs] [84500.513439] [<ffffffff811c7f79>] vfs_fsync_range+0x49/0xa0 [84500.519658] [<ffffffff811c802b>] do_fsync+0x3b/0x70 [84500.525197] [<ffffffff811c829b>] SyS_fsync+0xb/0x10 [84500.530728] [<ffffffff8157f04a>] entry_SYSCALL_64_fastpath+0x1e/0x8e [84500.537963] ---[ end trace 1080ee8b7ee410c1 ]--- [84500.543138] ------------[ cut here ]------------ [84500.548311] WARNING: CPU: 0 PID: 8593 at fs/btrfs/extent-tree.c:3489 btrfs_run_delayed_refs_and_get_processed+0x4b3/0x4d0 [btrfs]() [84500.561532] BTRFS: Transaction aborted (error -5) [84500.561555] Modules linked in: pci_stub vfio_pci vfio_virqfd vfio_iommu_type1 vfio vhost_net(O) kvm_intel kvm irqbypass nfnetlink tun xt_ipvs ip_vs_rr ip_vs xt_mark br_netfilter bridge stp cmac aufs macvlan veth ctr ccm xt_conntrack xt_addrtype ipt_MASQUERADE xt_REDIRECT nf_nat_masquerade_ipv4 xt_nat nf_nat_redirect xt_policy xfrm6_mode_transport xfrm4_mode_transport xfrm6_mode_tunnel xfrm4_mode_tunnel xfrm6_mode_beet xfrm4_mode_beet deflate authencesn ipcomp6 exfat(O) ipcomp xfrm6_tunnel xfrm4_tunnel fuse tunnel6 esp6 esp4 ah6 ah4 xfrm_ipcomp af_key xfrm_user xfrm_algo l2tp_ppp l2tp_core ppp_deflate bsd_comp ppp_mppe echainiv xt_TCPMSS iptable_mangle pppox ppp_async ppp_generic slhc 8021q vhost_scsi(O) vhost(O) tcm_loop(O) iscsi_target_mod(O) target_core_user(O) target_core_ep(O) target_core_multi_file(O) [84500.641627] target_core_file(O) target_core_iblock(O) target_core_mod(O) syno_extent_pool(PO) rodsp_ep(O) ch341(OE) cp210x(OE) cdc_acm ftdi_sio usbserial udf isofs cifs synoacl_vfs(PO) iptable_nat nf_nat_ipv4 nf_nat nf_conntrack_ipv6 ip6table_filter ip6_tables xt_recent xt_iprange xt_limit xt_state xt_tcpudp xt_multiport xt_LOG nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables x_tables nfsd btrfs ecryptfs zstd_decompress zstd_compress xxhash xor raid6_pq lockd grace rpcsec_gss_krb5 auth_rpcgss sunrpc leds_lp3943 aesni_intel glue_helper lrw gf128mul ablk_helper syno_hddmon(P) apollolake_synobios(PO) hid_generic usbhid hid usblp i915 drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops cfbfillrect cfbcopyarea cfbimgblt drm drm_panel_orientation_quirks iosf_mbi fb fbdev video backlight [84500.719447] button uhci_hcd ehci_pci ehci_hcd usb_storage r8168(O) i2c_algo_bit igb(O) e1000e(O) sg dm_snapshot dm_bufio crc_itu_t crc_ccitt psnap p8022 llc hfsplus md4 hmac sit tunnel4 openvswitch flashcache_syno(O) gre flashcache(O) syno_flashcache_control(O) nf_defrag_ipv6 ipv6 nf_conntrack dm_mod arc4 crc32c_intel cryptd ecb aes_x86_64 authenc des_generic ansi_cprng cts md5 cbc cpufreq_powersave cpufreq_performance acpi_cpufreq processor cpufreq_stats vxlan ip6_udp_tunnel udp_tunnel ip_tunnel loop sha256_generic synorbd(PO) synofsbd(PO) etxhci_hcd xhci_pci xhci_hcd usbcore usb_common [last unloaded: apollolake_synobios] [84500.780111] CPU: 0 PID: 8593 Comm: synosharesnapsh Tainted: P W OE 4.4.180+ #42962 [84500.789537] Hardware name: Synology DS218+/DS218+, BIOS M.135 11/11/2019 [84500.797009] 0000000000000000 ffff8802a5b47b78 ffffffff812f2dbd 0000000000000009 [84500.805281] ffff8802a5b47bc0 ffff8802a5b47bb0 ffffffff81051703 ffffffffa086e617 [84500.813550] ffff8804599d7bd0 0000000000000200 ffff8804599d7bd0 ffff880459b66000 [84500.821818] Call Trace: [84500.824543] [<ffffffff812f2dbd>] dump_stack+0x4d/0x70 [84500.830276] [<ffffffff81051703>] warn_slowpath_common+0x83/0xa0 [84500.836981] [<ffffffff81051769>] warn_slowpath_fmt+0x49/0x50 [84500.843409] [<ffffffffa079e7a1>] ? __btrfs_run_delayed_refs+0x1501/0x1900 [btrfs] [84500.851875] [<ffffffffa07a2953>] btrfs_run_delayed_refs_and_get_processed+0x4b3/0x4d0 [btrfs] [84500.861509] [<ffffffffa07bdfdc>] btrfs_commit_transaction+0x15c/0xf70 [btrfs] [84500.869575] [<ffffffff811304e5>] ? find_get_pages_tag+0xc5/0x170 [84500.876392] [<ffffffffa07dadbe>] btrfs_sync_file+0x22e/0x360 [btrfs] [84500.883586] [<ffffffff811c7f79>] vfs_fsync_range+0x49/0xa0 [84500.889805] [<ffffffff811c802b>] do_fsync+0x3b/0x70 [84500.895346] [<ffffffff811c829b>] SyS_fsync+0xb/0x10 [84500.900884] [<ffffffff8157f04a>] entry_SYSCALL_64_fastpath+0x1e/0x8e [84500.908107] ---[ end trace 1080ee8b7ee410c2 ]--- [84500.913274] BTRFS: error (device dm-0) in btrfs_run_delayed_refs_and_get_processed:3489: errno=-5 IO failure [84500.924284] BTRFS info (device dm-0): forced readonly [84620.126341] BTRFS error (device dm-0): Remounting read-write after error is not allowed I assume that there is some btrfs transaction that gets triggered or replayed once the folder is accessed, but I don't understand why this did not get triggered when I created the tar file from the same folder. I guess that there is some kind of btrfs command that would deal with this, but I don't want to just use any of the commands mentioned in the post above without knowing if it is applicable in my situation. Most importantly, I would like to know if it's possible to find out which file caused this problem and/or which files have actually been affected by this problem so I can get them back from backup. Any help is highly appreciated!