Re: Aborted transaction on invalid snapshot -i

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

-------- Original Message  --------
Subject: Aborted transaction on invalid snapshot -i
From: Remi Rampin <remirampin@gmail.com>
To: <linux-btrfs@vger.kernel.org>
Date: 2015年05月11日 12:05

> Hi list,
>
> I'm checking out the accounting/quota facilities of Btrfs, and stumbled
> on this crash. While I am technically misspelling arguments to the btrfs
> tool, it seems that getting an unknown error during the transaction and
> emergency RO remount is a bit much.
>
> Basically, "btrfs subvolume snapshot -i 0/100 /mnt/root /mnt/snap" is
> causing the error (I meant to type 1/100).
>
> Attached is a simple session reproducing the crash (every time on my
> machine), with output from btrfs commands and dmesg.
>
> Regards
>
>
> ----- session -----
>
> remram@missy:~$ uname -a
> Linux missy 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-3~deb8u1
> (2015-04-24) x86_64 GNU/Linux
> remram@missy:~$ /sbin/btrfs --version
> Btrfs v3.17
> remram@missy:~$ touch btdisk
> remram@missy:~$ chattr +C btdisk
> remram@missy:~$ truncate -s 200M btdisk
> remram@missy:~$ sudo losetup /dev/loop0 btdisk
> remram@missy:~$ sudo mkfs.btrfs /dev/loop0
> SMALL VOLUME: forcing mixed metadata/data groups
> Btrfs v3.17
> See http://btrfs.wiki.kernel.org for more information.
>
> Performing full device TRIM (200.00MiB) ...
> Turning ON incompat feature 'mixed-bg': mixed data and metadata block
> groups
> Turning ON incompat feature 'extref': increased hardlink limit per file
> to 65536
> Created a data/metadata chunk of size 8388608
> fs created label (null) on /dev/loop0
>          nodesize 4096 leafsize 4096 sectorsize 4096 size 200.00MiB
> remram@missy:~$ sudo mount /dev/loop0 /mnt
> remram@missy:~$ sudo btrfs quota enable /mnt
> remram@missy:~$ sudo btrfs subvolume create /mnt/root
> Create subvolume '/mnt/root'
> remram@missy:~$ sudo btrfs qgroup show /mnt
> qgroupid rfer excl
> -------- ---- ----
> 0/5      4096 4096
> 0/256    4096 4096
> remram@missy:~$ sudo btrfs subvolume snapshot -i 0/100 /mnt/root /mnt/snap
> Create a snapshot of '/mnt/root' in '/mnt/snap'
> ERROR: cannot snapshot '/mnt/root' - Invalid argument
> remram@missy:~$ mount
> ...
> /dev/loop0 on /mnt type btrfs (ro,relatime,space_cache)
> remram@missy:~$ dmesg
> ...
> [33474.410205] ------------[ cut here ]------------
> [33474.410244] WARNING: CPU: 4 PID: 18510 at
> /build/linux-RGM_Ed/linux-3.16.7-ckt9/fs/btrfs/super.c:259
> __btrfs_abort_transaction+0x4b/0x110 [btrfs]()
> [33474.410247] BTRFS: Transaction aborted (error -22)
> [33474.410248] Modules linked in: loop ctr ccm bnep pci_stub vboxpci(O)
> vboxnetadp(O) vboxnetflt(O) vboxdrv(O) nfsd auth_rpcgss oid_registry
> nfs_acl nfs lockd fscache sunrpc ecb btusb bluetooth 6lowpan_iphc crc16
> x86_pkg_temp_thermal intel_powerclamp arc4 intel_rapl coretemp joydev
> iwldvm kvm_intel kvm iTCO_wdt iTCO_vendor_support crc32_pclmul mac80211
> msi_wmi ghash_clmulni_intel sparse_keymap aesni_intel aes_x86_64 lrw
> gf128mul glue_helper ablk_helper cryptd rtsx_pci_ms processor memstick
> lpc_ich snd_hda_codec_hdmi ac battery snd_hda_codec_realtek pcspkr
> iwlwifi psmouse serio_raw cfg80211 rfkill mei_me mei i2c_i801 shpchp
> snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec
> evdev snd_hwdep snd_pcm snd_timer snd soundcore fuse parport_pc ppdev lp
> parport autofs4 btrfs xor raid6_pq hid_generic
> [33474.410308]  usbhid hid sg sd_mod crc_t10dif sr_mod crct10dif_generic
> cdrom rtsx_pci_sdmmc ahci libahci crct10dif_pclmul nouveau
> crct10dif_common crc32c_intel libata mxm_wmi i915 ttm i2c_algo_bit
> ehci_pci rtsx_pci sdhci_pci drm_kms_helper scsi_mod sdhci ehci_hcd
> xhci_hcd mmc_core drm alx mfd_core mdio usbcore i2c_core usb_common fan
> thermal video wmi thermal_sys button
> [33474.410347] CPU: 4 PID: 18510 Comm: btrfs Tainted: G        W  O
> 3.16.0-4-amd64 #1 Debian 3.16.7-ckt9-3~deb8u1
> [33474.410349] Hardware name: Micro-Star International Co., Ltd. GE60
> 0NC/GE60 0ND/MS-16GA, BIOS E16GAIMS.10E 07/11/2012
> [33474.410352]  0000000000000009 ffffffff8150ac96 ffff88012c6fba88
> ffffffff81067747
> [33474.410356]  00000000ffffffea ffff88012c6fbad8 ffff880122dd0f38
> ffffffffa057b070
> [33474.410360]  000000000000051b ffffffff810677ac ffffffffa057eaf8
> ffffffff00000020
> [33474.410364] Call Trace:
> [33474.410376]  [<ffffffff8150ac96>] ? dump_stack+0x41/0x51
> [33474.410383]  [<ffffffff81067747>] ? warn_slowpath_common+0x77/0x90
> [33474.410391]  [<ffffffff810677ac>] ? warn_slowpath_fmt+0x4c/0x50
> [33474.410406]  [<ffffffffa04d700b>] ?
> __btrfs_abort_transaction+0x4b/0x110 [btrfs]
> [33474.410426]  [<ffffffffa0502c88>] ?
> create_pending_snapshot+0x578/0x960 [btrfs]
> [33474.410443]  [<ffffffffa050224a>] ?
> btrfs_wait_pending_ordered+0x2a/0x100 [btrfs]
> [33474.410449]  [<ffffffff8150f5fe>] ? mutex_lock+0xe/0x2a
> [33474.410465]  [<ffffffffa05030f9>] ?
> create_pending_snapshots+0x89/0xb0 [btrfs]
> [33474.410482]  [<ffffffffa0504404>] ?
> btrfs_commit_transaction+0x394/0xa10 [btrfs]
> [33474.410499]  [<ffffffffa0504b10>] ? start_transaction+0x90/0x570 [btrfs]
> [33474.410520]  [<ffffffffa0536fea>] ?
> btrfs_mksubvol.isra.29+0x54a/0x5a0 [btrfs]
> [33474.410526]  [<ffffffff810a7930>] ? prepare_to_wait_event+0xf0/0xf0
> [33474.410544]  [<ffffffffa05371d1>] ?
> btrfs_ioctl_snap_create_transid+0x191/0x1a0 [btrfs]
> [33474.410561]  [<ffffffffa053733e>] ?
> btrfs_ioctl_snap_create_v2+0xee/0x140 [btrfs]
> [33474.410578]  [<ffffffffa05393cf>] ? btrfs_ioctl+0xcaf/0x2b10 [btrfs]
> [33474.410584]  [<ffffffff8136ebec>] ? pty_write+0x4c/0x50
> [33474.410588]  [<ffffffff810a74a2>] ? remove_wait_queue+0x12/0x50
> [33474.410592]  [<ffffffff81367c1a>] ? n_tty_write+0x37a/0x4e0
> [33474.410598]  [<ffffffff8109cda7>] ? put_prev_entity+0x57/0x350
> [33474.410602]  [<ffffffff8109bc16>] ? set_next_entity+0x56/0x70
> [33474.410608]  [<ffffffff811ba2ff>] ? do_vfs_ioctl+0x2cf/0x4b0
> [33474.410611]  [<ffffffff8150d1b1>] ? __schedule+0x2b1/0x710
> [33474.410615]  [<ffffffff811ba561>] ? SyS_ioctl+0x81/0xa0
> [33474.410620]  [<ffffffff81510e4d>] ?
> system_call_fast_compare_end+0x10/0x15
> [33474.410623] ---[ end trace a44935b638f9b25c ]---
> [33474.410627] BTRFS: error (device loop0) in
> create_pending_snapshot:1307: errno=-22 unknown
> [33474.410631] BTRFS info (device loop0): forced readonly
> [33474.410635] BTRFS warning (device loop0): Skipping commit of aborted
> transaction.
> [33474.410637] BTRFS: error (device loop0) in cleanup_transaction:1585:
> errno=-22 unknown
> [33474.410640] BTRFS info (device loop0): delayed_refs has NO entry

Confirmed in 4.0.

So definitely a bug.
I'll try to fix it soon.

Thanks,
Qu
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