From: James Pearson <james-p@moving-picture.com>
Subject: Re: mtab and procs not in sync?
Date: Wed, 09 Jun 2004 16:04:38 +0100
Sender: nfs-admin@lists.sourceforge.net
Message-ID: <40C72706.6050803@moving-picture.com>
References: <482A3FA0050D21419C269D13989C61130435E230@lavender-fe.eng.netapp.com>
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Cc: nfs@lists.sourceforge.net
To: "Lever, Charles" <Charles.Lever@netapp.com>
In-Reply-To: <482A3FA0050D21419C269D13989C61130435E230@lavender-fe.eng.netapp.com>
Errors-To: nfs-admin@lists.sourceforge.net

On a 2.4.26 kernel on x86 I can get /proc/mounts to go over 4K (over 8K 
with about 100 automounted file systems).

Having a quick look through the kernel code I can see seq_file used in 
relation to proc_mounts_operations (fs/proc/base.c) - however as I don't 
pretend to understand the code, I can't say this is the case ...

If 2.4.X does use seq_file, then is it safe to say /proc/mounts doesn't 
suffer from a truncation problem?

James Pearson

Lever, Charles wrote:
> as far as i can tell, the 4KB limit is common to x86 on 2.2 and 2.4.
> 2.6 has replaced the old /proc read method with seq_file, so i believe
> /proc/mounts on 2.6 kernels will not suffer from this problem.
> 
> it's not a fixed number of mounts, because the length of each line in
> /proc/mounts depends on what mount options are in effect.  the limit is
> the number of characters in the file.
> 
> 
>>-----Original Message-----
>>From: James Pearson [mailto:james-p@moving-picture.com] 
>>Sent: Wednesday, June 09, 2004 6:29 AM
>>To: Lever, Charles
>>Cc: nfs@lists.sourceforge.net
>>Subject: Re: [NFS] mtab and procs not in sync?
>>
>>
>>Do you know how many 'a lot of mounts' is?
>>
>>I believe there was a problem with /proc/mounts in 2.2 
>>kernels (limited 
>>to one page) - is there still a limit in 2.4 or 2.6 kernels?
>>
>>I currently symlink /proc/mounts to /etc/mtab on diskless machines to 
>>get round the issue that /etc/mtab can not trusted to be 
>>correct. I only 
>>have a maximum of a few 10's of mounts at any one time.
>>
>>James Pearson
>>
>>Lever, Charles wrote:
>>
>>>if there are a lot of mounts on the system, then 
>>
>>/proc/mounts can be 
>>
>>>truncated and not show all of them.
>>>
>>>however, if there are more mounts in /proc/mounts than in 
>>
>>/etc/mtab, 
>>
>>>there is probably a bug in mount.  not unheard of.
>>>
>>>
>>>
>>>>-----Original Message-----
>>>>From: Phy Prabab [mailto:phyprabab@yahoo.com]
>>>>Sent: Tuesday, June 08, 2004 2:21 PM
>>>>To: nfs@lists.sourceforge.net
>>>>Subject: [NFS] mtab and procs not in sync?
>>>>
>>>>
>>>>Hello,
>>>>
>>>>Have run into a situation where mtab does not match /proc/mounts in 
>>>>that mtab has numerous entries that have expired off and 
>>
>>removed, yet 
>>
>>>>does not show that it has been removed from mtab.  Is this 
>>
>>known and 
>>
>>>>is there a fix?
>>>>
>>>>Kernel 2.4.21 and 23
>>>>nfs-utils 1.06
>>>>automount 4.1.2
>>>>
>>>>Thanks!
>>>>Phy
>>>>
>>>>
>>>>	
>>>>		
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>>>
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> 
> 


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