I/O errors when trying to loop mount an image

[James Harris]

Command

  sudo mount -t vfat flop1 /mnt/flop1

fails. The image is readable but the log shows many I/O errors such as

May 12 07:57:24 us64a kernel: [69801.335823] print_req_error: I/O error, dev loop0, sector 0
May 12 07:57:24 us64a kernel: [69801.337707] print_req_error: I/O error, dev loop0, sector 0
May 12 07:57:24 us64a kernel: [69801.339521] FAT-fs (loop0): unable to read boot sector
May 12 07:57:24 us64a kernel: [69801.342063] print_req_error: I/O error, dev loop0, sector 0
May 12 07:57:24 us64a kernel: [69801.343891] Buffer I/O error on dev loop0, logical block 0, async page read
May 12 07:57:24 us64a kernel: [69801.345974] print_req_error: I/O error, dev loop0, sector 1
May 12 07:57:24 us64a kernel: [69801.347832] Buffer I/O error on dev loop0, logical block 1, async page read
May 12 07:57:24 us64a kernel: [69801.349928] print_req_error: I/O error, dev loop0, sector 2
May 12 07:57:24 us64a kernel: [69801.351818] Buffer I/O error on dev loop0, logical block 2, async page read
May 12 07:57:24 us64a kernel: [69801.356103] print_req_error: I/O error, dev loop0, sector 3
May 12 07:57:24 us64a kernel: [69801.356109] Buffer I/O error on dev loop0, logical block 3, async page read
May 12 07:57:24 us64a kernel: [69801.356117] print_req_error: I/O error, dev loop0, sector 4
May 12 07:57:24 us64a kernel: [69801.356119] Buffer I/O error on dev loop0, logical block 4, async page read
May 12 07:57:24 us64a kernel: [69801.356122] print_req_error: I/O error, dev loop0, sector 5
May 12 07:57:24 us64a kernel: [69801.356125] Buffer I/O error on dev loop0, logical block 5, async page read
May 12 07:57:24 us64a kernel: [69801.356128] print_req_error: I/O error, dev loop0, sector 6
May 12 07:57:24 us64a kernel: [69801.356130] Buffer I/O error on dev loop0, logical block 6, async page read
May 12 07:57:24 us64a kernel: [69801.356134] print_req_error: I/O error, dev loop0, sector 7
May 12 07:57:24 us64a kernel: [69801.356136] Buffer I/O error on dev loop0, logical block 7, async page read
May 12 07:57:24 us64a kernel: [69801.356260] Buffer I/O error on dev loop0, logical block 0, async page read
May 12 07:57:24 us64a kernel: [69801.356263] Buffer I/O error on dev loop0, logical block 1, async page read

The command, understandably, reports "can't read superblock on /dev/loop0". The problem happens even on newly created images. Here's a sample set of commands and responses:

$ mkfs.msdos -C flop1 1440
$ ls -l
-rwxrwxrwx 1 root root 1474560 May 10 18:49 flop1
$ hd flop1
<--- output looks reasonable including 55 aa and two FATs --->
$ sudo mkdir /mnt/flop1
$ sudo mount -o loop flop1 /mnt/flop1
mount: /mnt/flop1: can't read superblock on /dev/loop0.
$ losetup -f
/dev/loop0
$

I see plenty of reports of similar on different websites but without resolution, including one on Launchpad but where the OP stopped responding so it did not get resolved. I don't know when this problem started to occur on this machine.

If it's relevant, this is running under VirtualBox which reports itself as Version 5.2.26 r128414 (Qt5.6.2) with their 'host extensions' enabled. However, mounting a floppy image previously worked on this virtual machine.

I have rebooted with /forcefsck to check the root (and only) filesystem. I have upgraded to the latest LTS Ubuntu, as below, but the problem persists.

System info:

No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.2 LTS
Release: 18.04
Codename: bionic

Linux us64a 4.18.0-18-generic #19~18.04.1-Ubuntu SMP Fri Apr 5 10:22:13 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

The machine is command-line only, i.e. no windowing.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1828712/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]

[James Harris (james-harris-1-h)]

Setting package to linux kernel as advised for a filesystem issue.

Ran apport-collect -p linux 1828712 per the instructions but I don't know that it worked as machine has no GUI.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1828712

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[James Harris (james-harris-1-h)]

Sorry I cannot run apport-collect as the machine has no GUI. I have tried the command on the console and via ssh but the resulting text-mode screen seems to prevent me entering my email address to log in.

I also tried apport-cli but it had the same problem with the same authentication screen.

As for logs, I did include the relevant syslog entries in the original report, if that helps.

[Brian Murray (brian-murray)]

apport-cli contains an option for save the report from another machine. apport-cli --help says:

  --save=PATH In bug filing mode, save the collected information
                        into a file instead of reporting it. This file can
                        then be reported later on from a different machine.

and:

  -c PATH, --crash-file=PATH
                        Report the crash from given .apport or .crash file
                        instead of the pending ones in /var/crash. (Implied if
                        file is given as only argument.)

However, this doesn't work with apport-collect but if the Ubuntu Kernel Bot still wants this you could open a new bug report using --save and the --crash-file.

[James Harris (james-harris-1-h)]

@brian-murray thanks for the suggestion. Have done you suggest but apport-cli on the system with the GUI does not seem to allow an existing bug to be updated with the info, so rather than generating a new bug report am copying the file generated by apport-cli --save below.

ProblemType: Bug
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
Date: Fri May 17 10:50:14 2019
Dependencies:
 adduser 3.116ubuntu1
 apt 1.6.10
 apt-utils 1.6.10
 busybox-initramfs 1:1.27.2-2ubuntu3.2
 ca-certificates 20180409
 coreutils 8.28-1ubuntu1
 cpio 2.12+dfsg-6
 debconf 1.5.66
 debconf-i18n 1.5.66
 dmsetup 2:1.02.145-4.1ubuntu3
 dpkg 1.19.0.5ubuntu2.1
 fdisk 2.31.1-0.4ubuntu3.3
 gcc-8-base 8.3.0-6ubuntu1~18.04
 gettext-base 0.19.8.1-6ubuntu0.3
 gpgv 2.2.4-1ubuntu1.2
 grub-common 2.02-2ubuntu8.13
 grub-gfxpayload-lists 0.7
 grub-pc 2.02-2ubuntu8.13
 grub-pc-bin 2.02-2ubuntu8.13
 grub2-common 2.02-2ubuntu8.13
 init-system-helpers 1.51
 initramfs-tools 0.130ubuntu3.7
 initramfs-tools-bin 0.130ubuntu3.7
 initramfs-tools-core 0.130ubuntu3.7
 klibc-utils 2.0.4-9ubuntu2
 kmod 24-1ubuntu3.2
 libacl1 2.2.52-3build1
 libapt-inst2.0 1.6.10
 libapt-pkg5.0 1.6.10
 libattr1 1:2.4.47-2build1
 libaudit-common 1:2.8.2-1ubuntu1
 libaudit1 1:2.8.2-1ubuntu1
 libblkid1 2.31.1-0.4ubuntu3.3
 libbz2-1.0 1.0.6-8.1
 libc6 2.27-3ubuntu1
 libcap-ng0 0.7.7-3.1
 libdb5.3 5.3.28-13.1ubuntu1
 libdevmapper1.02.1 2:1.02.145-4.1ubuntu3
 libfdisk1 2.31.1-0.4ubuntu3.3
 libffi6 3.2.1-8
 libfreetype6 2.8.1-2ubuntu2
 libfuse2 2.9.7-1ubuntu1
 libgcc1 1:8.3.0-6ubuntu1~18.04
 libgcrypt20 1.8.1-4ubuntu1.1
 libgmp10 2:6.1.2+dfsg-2
 libgnutls30 3.5.18-1ubuntu1
 libgpg-error0 1.27-6
 libgpm2 1.20.7-5
 libhogweed4 3.4-1
 libidn2-0 2.0.4-1.1build2
 libklibc 2.0.4-9ubuntu2
 libkmod2 24-1ubuntu3.2
 liblocale-gettext-perl 1.07-3build2
 liblz4-1 0.0~r131-2ubuntu3
 liblzma5 5.2.2-1.3
 libmount1 2.31.1-0.4ubuntu3.3
 libncurses5 6.1-1ubuntu1.18.04
 libncursesw5 6.1-1ubuntu1.18.04
 libnettle6 3.4-1
 libp11-kit0 0.23.9-2
 libpam-modules 1.1.8-3.6ubuntu2.18.04.1
 libpam-modules-bin 1.1.8-3.6ubuntu2.18.04.1
 libpam0g 1.1.8-3.6ubuntu2.18.04.1
 libpcre3 2:8.39-9
 libpng16-16 1.6.34-1ubuntu0.18.04.2
 libprocps6 2:3.3.12-3ubuntu1.1
 libseccomp2 2.3.1-2.1ubuntu4.1
 libselinux1 2.7-2build2
 libsemanage-common 2.7-2build2
 libsemanage1 2.7-2build2
 libsepol1 2.7-1
 libsmartcols1 2.31.1-0.4ubuntu3.3
 libssl1.1 1.1.0g-2ubuntu4.3
 libstdc++6 8.3.0-6ubuntu1~18.04
 libsystemd0 237-3ubuntu10.21
 libtasn1-6 4.13-2
 libtext-charwidth-perl 0.04-7.1
 libtext-iconv-perl 1.7-5build6
 libtext-wrapi18n-perl 0.06-7.1
 libtinfo5 6.1-1ubuntu1.18.04
 libudev1 237-3ubuntu10.21
 libunistring2 0.9.9-0ubuntu2
 libuuid1 2.31.1-0.4ubuntu3.3
 libzstd1 1.3.3+dfsg-2ubuntu1
 linux-base 4.5ubuntu1
 linux-modules-4.18.0-18-generic 4.18.0-18.19~18.04.1
 lsb-base 9.20170808ubuntu1
 openssl 1.1.0g-2ubuntu4.3
 os-prober 1.74ubuntu1
 passwd 1:4.5-1ubuntu2
 perl-base 5.26.1-6ubuntu0.3
 procps 2:3.3.12-3ubuntu1.1
 psmisc 23.1-1ubuntu0.1
 sensible-utils 0.0.12
 tar 1.29b-2ubuntu0.1
 ubuntu-keyring 2018.09.18.1~18.04.0
 ucf 3.0038
 udev 237-3ubuntu10.21
 update-motd 3.6-0ubuntu1
 util-linux 2.31.1-0.4ubuntu3.3
 uuid-runtime 2.31.1-0.4ubuntu3.3
 zlib1g 1:1.2.11.dfs...

[codywohlers (codywohlers)]

possibly related:

This happened to me too after I resized an ext4 image file from 50G to 99G. Ever since then when I mount it I get the same error except starting a higher sector. If I unmount it and mount it again I get errors for different sectors. And `e2fsck -f` didn't find any error on the image.

`EXT4-fs (loop3): mounted filesystem with ordered data mode. Opts: (null)
print_req_error: I/O error, dev loop3, sector 197148928
print_req_error: I/O error, dev loop3, sector 197153024
...`

system:
`Ubuntu 18.04.4 LTS bionic
Linux 4.15.0-91-generic x86_64
libmount1:amd64 2.31.1-0.4ubuntu3.6`

[codywohlers (codywohlers)]

Update: My `print_req_error: I/O error` errors went away after writing some files to the image, unmounting it and running `e2fsck -f` again. No errors reported from e2fsck but after I didn't get the print_req errors anymore.