Re: "Too many levels of symbolic links"

[Donald Buczek <buczek@molgen.mpg.de>]

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Am 02.03.2014 10:41, schrieb Ian Kent:
> On Sun, 2014-03-02 at 09:28 +0100, Donald Buczek wrote:
>> Am 02.03.2014 03:17, schrieb Ian Kent:
>>> mnt_hash->next == mnt_hash->prev, mount has been unlinked from the mount
>>> tree so is not "visible". As far as we are concerned this mount has
>>> gone.
>> No, prev and next both point to the list_head in the mount_hashtable.
> Fair call, ->mnt_mp != NULL too which implies the mount hasn't been
> unlinked.

The problem is, that the mount is in another namespace. I've put mnt_ns 
into my perl script:

> root:kasslerbraten:/home/buczek/autofs/# ./peekmounts |grep mariux32
>  mountpoint 0xffff880125e44480 : count=   1 denty=0xffff88007c86da10 
> (mariux32)
>  struct mount 0xffff8800a3a9a6c0 : mountpoint dentry 
> 0xffff88007c86da10 (mariux32) mountpoint struct 0xffff880125e44480 NS 
> 0xffff8801271f9300
> root:kasslerbraten:/home/buczek/autofs/# ./peekmounts |grep project
>  mountpoint 0xffff8800c1d068a0 : count=   2 denty=0xffff8800c8b2e450 
> (project)
>  struct mount 0xffff8800c9e5e200 : mountpoint dentry 
> 0xffff8800c8b2e450 (project) mountpoint struct 0xffff8800c1d068a0 NS 
> 0xffff88012d00ed00
>  struct mount 0xffff8800a3a9a940 : mountpoint dentry 
> 0xffff8800c8b2e450 (project) mountpoint struct 0xffff8800c1d068a0 NS 
> 0xffff8801271f9300

We have a /project without a mounted /project/mariux32 and a /project 
with a mounted /project/mariux32 in another namespace.

This goes in the direction you mentioned in your other mail ("Illegal as 
far as autofs is concerned because an autofs mount is strictly 
associated with a path defined by its map") The system-wide, absolute 
semantics of pathnames in the automount world don't fit well into the 
process-local, relative mount semantics of the kernel.

I still don't know, where these "root" or "old-root" messages come from, 
but again the error occured after these strange messages appeared

> 2014-02-28T12:33:08.461073+01:00 kasslerbraten kernel: [13093.129511] 
> pid 7670: d_set_mounted: set mounted on dentry=ffff88007ca58a50 root
> 2014-02-28T12:33:08.461074+01:00 kasslerbraten kernel: [13093.129569] 
> pid 7670: put_mountpoint: mp=ffff8801271f9338
> 2014-02-28T12:33:08.461075+01:00 kasslerbraten kernel: [13093.129574] 
> pid 7670: d_set_mounted: dentry=ffff8800c890ce10 tmp
> 2014-02-28T12:33:08.461076+01:00 kasslerbraten kernel: [13093.129575] 
> pid 7670: d_set_mounted: set mounted on dentry=ffff8800c890ce10 tmp
> 2014-02-28T12:33:08.461077+01:00 kasslerbraten kernel: [13093.129578] 
> pid 7670: put_mountpoint: mp=ffff8801271f9338
> 2014-02-28T12:33:08.461078+01:00 kasslerbraten kernel: [13093.129599] 
> pid 7670: d_set_mounted: dentry=ffff88007ca407d0 old-root-D0k5jB
> 2014-02-28T12:33:08.461079+01:00 kasslerbraten kernel: [13093.129601] 
> pid 7670: d_set_mounted: set mounted on dentry=ffff88007ca407d0 
> old-root-D0k5jB
> 2014-02-28T12:33:08.461080+01:00 kasslerbraten kernel: [13093.129602] 
> pid 7670: put_mountpoint: mp=ffff8800c9e5e750
> 2014-02-28T12:33:08.461081+01:00 kasslerbraten kernel: [13093.129603] 
> pid 7670: put_mountpoint: cleared mounted on dentry=ffff88007ca58a50 root
> 2014-02-28T12:33:08.461082+01:00 kasslerbraten kernel: [13093.129604] 
> pid 7670: put_mountpoint: mp=ffff8800c9e5e610
> 2014-02-28T12:33:08.461082+01:00 kasslerbraten kernel: [13093.129662] 
> pid 7670: put_mountpoint: mp=0000014800450045
> 2014-02-28T12:33:08.461083+01:00 kasslerbraten kernel: [13093.129663] 
> pid 7670: put_mountpoint: mp=0000000000000006

(as explained in another mail , the addresses of "mp=" are wrong, so 
don't worry about these)

This looks like chroot or somesuch. But I have no idea. I don't find 
\"root or \"old- in any sources. There is not "root" in any map.

Hmmm. Isn't the daemon doing lazy umounts? Could it be this?
I've compiled the daemon with --enable-ignore-busy
Anything forcing the daemon to restart?
systemd doing stupid things to the daemon or the filesystem?

> [Service]
> Type=forking
> ExecStartPre=/sbin/make-automaps
> ExecStart=/usr/sbin/automount -v
> PIDFile=/run/autofs-running
> ExecReload=/bin/kill -HUP $MAINPID

   Donald

-- 
Donald Buczek
buczek@molgen.mpg.de
Tel: +49 30 8413 1433



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