Bind mounts record fstype of none

DISCUSSION Phillip Susi 5 participants 17 messages Oct 30, 2013 – Oct 31, 2013 Util-Linux package

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Phillip Susi

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2013-10-30 15:16 UTC #0 lore raw

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I came across an old bug filed in debian noting that mount records the fstype for bind mounts as 'none' and this causes df to suppress showing it. This seems like an error to me. The type should be what the actual filesystem type is, and if df wants to suppress showing bind mounts, it should do so based on the bind flag.

Thoughts?

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Bernhard Voelker

2013-10-30 15:40 UTC #1 lore raw

Quoted 10 lines · Phillip Susi

I came across an old bug filed in debian noting that mount records the fstype for bind mounts as 'none' and this causes df to suppress showing it. This seems like an error to me. The type should be what the actual filesystem type is, and if df wants to suppress showing bind mounts, it should do so based on the bind flag.
Thoughts?

yes, df(1) is from coreutils. ;-)

However, latest df(1) will skip such bind mounts per default - but now because of some 'bind' information (which is not available anyway), but just because it skips "duplicates" based on the device numbers. For the same device number, it will output that with the shortest mount point name.
You have to use -a to see all.

Have a nice day,
Berny

Phillip Susi

author

2013-10-30 15:59 UTC #2 lore raw

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Quoted 7 lines · Bernhard Voelker

yes, df(1) is from coreutils. ;-)
However, latest df(1) will skip such bind mounts per default - but now because of some 'bind' information (which is not available anyway), but just because it skips "duplicates" based on the device numbers. For the same device number, it will output that with the shortest mount point name. You have to use -a to see all.

So is mount wrong for recording the filesystem type as 'none' or not?

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Bernhard Voelker

2013-10-30 16:23 UTC #3 lore raw

Quoted 6 lines · Phillip Susi

Quoted 5 lines · Bernhard Voelker
yes, df(1) is from coreutils. ;-)
However, latest df(1) will skip such bind mounts per default - but now because of some 'bind' information (which is not available

typo: s/now/not/, of course.

Quoted 5 lines

Quoted 3 lines
anyway), but just because it skips "duplicates" based on the device numbers. For the same device number, it will output that with the shortest mount point name. You have to use -a to see all.
So is mount wrong for recording the filesystem type as 'none' or not?

Where do you see 'none'?

$ df /home
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sdb        10321208 1233056   8563864  13% /home

$ mkdir /tmp/home

$ mount -o bind /home /tmp/home

$ df -a | grep home
/dev/sdb        10321208 1233056   8563864  13% /home
/dev/sdb        10321208 1233056   8563864  13% /tmp/home

$ mount | grep home
/dev/sdb on /home type ext4 (rw,relatime,data=ordered)
/dev/sdb on /tmp/home type ext4 (rw,relatime,data=ordered)

$ grep home /proc/mounts /proc/self/mountinfo /proc/self/mounts
/proc/mounts:/dev/sdb /home ext4 rw,relatime,data=ordered 0 0
/proc/mounts:/dev/sdb /tmp/home ext4 rw,relatime,data=ordered 0 0
/proc/self/mountinfo:40 21 8:16 / /home rw,relatime shared:24 - ext4 /dev/sdb
rw,data=ordered
/proc/self/mountinfo:109 21 8:16 / /tmp/home rw,relatime shared:24 - ext4
/dev/sdb rw,data=ordered
/proc/self/mounts:/dev/sdb /home ext4 rw,relatime,data=ordered 0 0
/proc/self/mounts:/dev/sdb /tmp/home ext4 rw,relatime,data=ordered 0 0

[That was on kernel 3.7.10 of openSUSE-12.3,
mount/df built from {util-linux,coreutils}.git]

Have a nice day,
Berny

Helmut Hullen

2013-10-30 16:39 UTC #4 lore raw

Hallo, Bernhard,

Du meintest am 30.10.13:

Quoted 4 lines

Quoted 2 lines
So is mount wrong for recording the filesystem type as 'none' or not?
Where do you see 'none'?

df -a -T

Maybe that problem is related to the option "-type"; "bind" is no allowed "type".

Viele Gruesse!
Helmut

Dave Reisner

2013-10-30 16:45 UTC #5 lore raw

Quoted 7 lines · Helmut Hullen

Hallo, Bernhard,
Du meintest am 30.10.13:
Quoted 2 lines
Quoted 2 lines
So is mount wrong for recording the filesystem type as 'none' or not?

Quoted 6 lines

Quoted 1 line
Where do you see 'none'?
df -a -T
Maybe that problem is related to the option "-type"; "bind" is no allowed "type".

The fstype of "none" only shows up on older systems where mtab is a regular file and not a symlink to /proc/self/mounts.

Cheers,
Dave

Helmut Hullen

2013-10-30 19:37 UTC #6 lore raw

Hallo, Dave,

Du meintest am 30.10.13:

[...]

Quoted 9 lines

Quoted 6 lines
Quoted 1 line
Where do you see 'none'?
df -a -T
Maybe that problem is related to the option "-type"; "bind" is no allowed "type".
The fstype of "none" only shows up on older systems where mtab is a regular file and not a symlink to /proc/self/mounts.

Yes - that's the difference on my system ("mtab" is a regular file).

Viele Gruesse!
Helmut

Bernhard Voelker

2013-10-30 16:48 UTC #7 lore raw

In reply to Helmut Hullen

Quoted 6 lines · Helmut Hullen

Quoted 4 lines
Du meintest am 30.10.13:
Quoted 2 lines
So is mount wrong for recording the filesystem type as 'none' or not?

Quoted 6 lines

Quoted 1 line
Where do you see 'none'?
df -a -T
Maybe that problem is related to the option "-type"; "bind" is no allowed "type".

I don't get that.
Is it possible you hit the "mtab is evil" (TM Kzak) issue?
http://karelzak.blogspot.de/2011_04_01_archive.html

Have a nice day,
Berny

Phillip Susi

author

2013-10-30 19:10 UTC #8 lore raw

In reply to Bernhard Voelker

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Quoted 7 lines · Bernhard Voelker

Where do you see 'none'?

$ df /home Filesystem     1K-blocks    Used Available Use% Mounted
on /dev/sdb        10321208 1233056   8563864  13% /home

$ mkdir /tmp/home

Quoted 8 lines

$ mount -o bind /home /tmp/home

$ df -a | grep home /dev/sdb        10321208 1233056   8563864  13%
/home /dev/sdb        10321208 1233056   8563864  13% /tmp/home

$ mount | grep home /dev/sdb on /home type ext4
(rw,relatime,data=ordered) /dev/sdb on /tmp/home type ext4
(rw,relatime,data=ordered)

I see none in the output of mount and df. Just rebuilt from git head to make sure and still says none.

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Helmut Hullen

2013-10-30 16:13 UTC #9 lore raw

In reply to Phillip Susi

Hallo, Phillip,

Du meintest am 30.10.13:

Quoted 5 lines

I came across an old bug filed in debian noting that mount records the fstype for bind mounts as 'none' and this causes df to suppress showing it. This seems like an error to me. The type should be what the actual filesystem type is, and if df wants to suppress showing bind mounts, it should do so based on the bind flag.

For seeing "bind" I'd prefer

mount

mount | grep -w bind

Viele Gruesse!
Helmut

Karel Zak

maintainer

2013-10-31 10:57 UTC #10 lore raw

In reply to Phillip Susi

Quoted 5 lines · Phillip Susi

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I came across an old bug filed in debian noting that mount records the fstype for bind mounts as 'none' and this causes df to suppress

It was explicitly requested by Al Viro to use "none" for some VFS operations years ago (c4966ccb16868fa748009a826340fac9d1b1ce39, 0fae284a7a13d4d2dba7a908e0662a6d9c46f877).

I think it's correct, because FS type does not make any sense there and it's waste of time to try to determine FS type for MS_BINS or MS_PROPAGATION operations.

Quoted 3 lines

showing it. This seems like an error to me. The type should be what the actual filesystem type is, and if df wants to suppress showing bind mounts, it should do so based on the bind flag.

Seems like you're victim of the mtab file. My Fedora 19:

    # mount --bind /home /mnt/test
    # mount | grep /mnt/test
    /dev/sda5 on /mnt/test type ext4 (rw,relatime,data=ordered)

Karel

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 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com

Phillip Susi

author

2013-10-31 14:18 UTC #11 lore raw

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Quoted 7 lines · Karel Zak

Quoted 5 lines · Phillip Susi
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I came across an old bug filed in debian noting that mount records the fstype for bind mounts as 'none' and this causes df to suppress

Quoted 7 lines

It was explicitly requested by Al Viro to use "none" for some VFS operations years ago (c4966ccb16868fa748009a826340fac9d1b1ce39, 0fae284a7a13d4d2dba7a908e0662a6d9c46f877).
I think it's correct, because FS type does not make any sense there and it's waste of time to try to determine FS type for MS_BINS or MS_PROPAGATION operations.

How does it not make sense?

Quoted 8 lines

Quoted 3 lines
showing it. This seems like an error to me. The type should be what the actual filesystem type is, and if df wants to suppress showing bind mounts, it should do so based on the bind flag.
Seems like you're victim of the mtab file. My Fedora 19:
# mount --bind /home /mnt/test # mount | grep /mnt/test /dev/sda5
on /mnt/test type ext4 (rw,relatime,data=ordered)

Since the kernel reports the correct type, then I'd say mount should behave the same when using mtab, and record it right instead of forcing it to none.

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Karel Zak

maintainer

2013-10-31 15:10 UTC #12 lore raw

Quoted 15 lines · Phillip Susi

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Quoted 11 lines · Karel Zak
Quoted 5 lines · Phillip Susi
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I came across an old bug filed in debian noting that mount records the fstype for bind mounts as 'none' and this causes df to suppress
It was explicitly requested by Al Viro to use "none" for some VFS operations years ago (c4966ccb16868fa748009a826340fac9d1b1ce39, 0fae284a7a13d4d2dba7a908e0662a6d9c46f877).

Quoted 5 lines

Quoted 3 lines
I think it's correct, because FS type does not make any sense there and it's waste of time to try to determine FS type for MS_BINS or MS_PROPAGATION operations.
How does it not make sense?

It is not FS operation, FS type is completely irrelevant here, kernel does not use this argument of the mount(2) syscall.

Quoted 4 lines

Quoted 4 lines
Quoted 3 lines
showing it. This seems like an error to me. The type should be what the actual filesystem type is, and if df wants to suppress showing bind mounts, it should do so based on the bind flag.

Quoted 8 lines

Quoted 4 lines
Seems like you're victim of the mtab file. My Fedora 19:
# mount --bind /home /mnt/test # mount | grep /mnt/test /dev/sda5
on /mnt/test type ext4 (rw,relatime,data=ordered)
Since the kernel reports the correct type, then I'd say mount should behave the same when using mtab, and record it right instead of forcing it to none.

There is *many disadvantages* when you use mtab, not sure if it make sense to fix the issues especially when mtab is currently unused by (almost) all distributions.

Maybe we can keep the fstype and not replace it with "none" for mtab, but is it so important when we use "none" since 2009 and mtab is almost dead?

Karel

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 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com

Phillip Susi

author

2013-10-31 15:28 UTC #13 lore raw

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Quoted 7 lines · Karel Zak

There is *many disadvantages* when you use mtab, not sure if it make sense to fix the issues especially when mtab is currently unused by (almost) all distributions.
Maybe we can keep the fstype and not replace it with "none" for mtab, but is it so important when we use "none" since 2009 and mtab is almost dead?

I know there were a number of issues with this transition, have they all been worked out at this point? Is all you need to do to make the switch is replace /etc/mtab with a symlink to /proc/mounts? Maybe I'll try doing that.

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Karel Zak

maintainer

2013-10-31 16:51 UTC #14 lore raw

Quoted 8 lines · Phillip Susi

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Quoted 4 lines · Karel Zak
There is *many disadvantages* when you use mtab, not sure if it make sense to fix the issues especially when mtab is currently unused by (almost) all distributions.

Quoted 8 lines

Quoted 3 lines
Maybe we can keep the fstype and not replace it with "none" for mtab, but is it so important when we use "none" since 2009 and mtab is almost dead?
I know there were a number of issues with this transition, have they all been worked out at this point? Is all you need to do to make the switch is replace /etc/mtab with a symlink to /proc/mounts? Maybe I'll try doing that.

Yes, the symlink and libmount based mount(8). We had some issues with df(1) but I guess all is resolved by recent coreutils.

Karel

Signature · 2 lines

 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com

Karel Zak

maintainer

2013-10-31 16:53 UTC #15 lore raw

In reply to Phillip Susi

Quoted 8 lines · Phillip Susi

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Quoted 4 lines · Karel Zak
There is *many disadvantages* when you use mtab, not sure if it make sense to fix the issues especially when mtab is currently unused by (almost) all distributions.

Quoted 8 lines

Quoted 3 lines
Maybe we can keep the fstype and not replace it with "none" for mtab, but is it so important when we use "none" since 2009 and mtab is almost dead?
I know there were a number of issues with this transition, have they all been worked out at this point? Is all you need to do to make the switch is replace /etc/mtab with a symlink to /proc/mounts? Maybe I'll try doing that.

... and it's also good to link mount.nfs from nfs-utils with libmount as NFS maintains some mount options in userspace (in this case we use private library /run/mount/utab file).

Karel

Signature · 2 lines

 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com

Karel Zak

maintainer

2013-10-31 15:19 UTC #16 lore raw

In reply to Phillip Susi

Quoted 1 line · Phillip Susi

Quoted 1 line
Quoted 1 line
I came across an old bug filed in debian

I forgot... Thanks! We had very good relationship with Debian (thanks to LaMont Jones), but in last 5 years it seems that nobody from Debian camp cares. It's strange as Debian plays important role in Linux world.

Karel

Signature · 2 lines

 Karel Zak  <[email protected]>
 http://karelzak.blogspot.com