On 10/24/2013 2:07 PM, Vyacheslav Dubeyko wrote:
> Hi Michael,
>
> On Oct 24, 2013, at 9:21 PM, Michael Conrad wrote:
>
>>   /dev/sdb4 on /mnt/_bak type nilfs2 (rw,relatime)
>>   /dev/sdb4 on /mnt/sdb4 type nilfs2 (rw,relatime)
>>
>> I saw this in Linux 3.2.16, then upgraded to 3.10.7 and it still happens.  Writing to these mounts in parallel causes buggy behavior, though it didn't corrupt my partition (yet).
> I can't reproduce such behavior. Could you describe your environment and
> reproducing path in more details?
>
> Thanks,
> Vyacheslav Dubeyko.

System 1:


uname -a
   Linux mlcdev 3.2.12-gentoo #10 SMP Fri Oct 18 22:00:41 UTC 2013 i686 
Intel(R) Xeon(R) CPU           X3220  @ 2.40GHz GenuineIntel GNU/Linux

mount.nilfs2 -V
   mount.nilfs2 (nilfs-utils 2.1.5)

System 2:

uname -a
   Linux conserv 3.10.7-gentoo-r1 #1 SMP Wed Oct 23 18:50:52 EDT 2013 
i686 Intel(R) Core(TM)2 Quad CPU Q8300 @ 2.50GHz GenuineIntel GNU/Linux

mount.nilfs2 -V
   mount.nilfs2 (nilfs-utils 2.1.5)

These are both 32-bit systems, running kernels from "gentoo-sources" 
(which are mostly vanilla).

My steps were very simple:

   mkfs -t nilfs2 -L SNAPSHOT /dev/sdb4
   mount /dev/sdb4 /mnt/a
   mount /dev/sdb4 /mnt/b

Mount.nilfs2 reports the error, but the filesystem gets mounted twice in 
rw mode.

# cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/sda2 / ext4 rw,noatime,data=ordered 0 0
proc /proc proc rw,relatime 0 0
tmpfs /run tmpfs rw,nosuid,nodev,relatime,mode=755 0 0
udev /dev devtmpfs 
rw,nosuid,relatime,size=10240k,nr_inodes=127686,mode=755 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620 0 0
shm /dev/shm tmpfs rw,nosuid,nodev,noexec,relatime 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
/dev/sdb2 /mnt/var ext4 rw,noatime,data=ordered 0 0
/dev/loop0 /usr/portage squashfs ro,nosuid,nodev,noexec,relatime 0 0
/dev/sdb4 /mnt/a nilfs2 rw,relatime 0 0
/dev/sdb4 /mnt/b nilfs2 rw,relatime 0 0

Even the cleaner gets started twice:

# ps ax | grep nil
  9646 ?        Ss     0:00 /sbin/nilfs_cleanerd -n /dev/sdb4 /mnt/a
  9649 ?        Ss     0:00 /sbin/nilfs_cleanerd -n /dev/sdb4 /mnt/b
  9656 pts/1    S+     0:00 grep --colour=auto nil

I've attached my kernel config for System 2, if you're interested.

-Mike