[LTP] [PATCH] lsmod01: parse a copy of /proc/modules

[Stanislav Kholmanskikh]

On 08/29/2016 04:34 PM, Jan Stancek wrote:
> 
> 
> 
> 
> ----- Original Message -----
>> From: "Stanislav Kholmanskikh" <stanislav.kholmanskikh@oracle.com>
>> To: "Cyril Hrubis" <chrubis@suse.cz>
>> Cc: "vasily isaenko" <vasily.isaenko@oracle.com>, ltp@lists.linux.it
>> Sent: Monday, 29 August, 2016 3:05:11 PM
>> Subject: Re: [LTP] [PATCH] lsmod01: parse a copy of /proc/modules
>>
>>
>>
>> On 08/29/2016 03:50 PM, Cyril Hrubis wrote:
>>> Hi!
>>>> In my environment, if TMPDIR is on NFSv4, this test case fails with:
>>>>
>>>> lsmod01 1 TFAIL : lsmod output different from /proc/modules.
>>>>   21c21
>>>>   < sunrpc 207591 28
>>>>   ---
>>>>   > sunrpc 207591 29
>>>>
>>>> To avoid such problems I separate the process of getting data from
>>>> /proc/modules and the process of parsing it in the pipe structure.
>>>
>>> So the sunrpc module gets its ref counter incremented from somewhere of
>>> the nfs kernel code once we open file on NFS?
>>
>> Looks so. I hava a share mounted from localhost:
>>
>> [root@skholman-m7 mnt]# mount|grep mnt
>> 127.0.0.1:/opt on /mnt type nfs
>> (rw,vers=4,addr=127.0.0.1,clientaddr=127.0.0.1)
>> [root@skholman-m7 mnt]# awk '{print $1, $2, $3}' /proc/modules|sort >
>> /tmp/not_nfs
>> [root@skholman-m7 mnt]# awk '{print $1, $2, $3}' /proc/modules|sort > nfs
>> [root@skholman-m7 mnt]# grep sunrpc nfs
>> sunrpc 207591 29
>> [root@skholman-m7 mnt]# grep sunrpc /tmp/not_nfs
>> sunrpc 207591 28
>> [root@skholman-m7 mnt]#
> 
> And if you do that with just "cat /proc/modules", then there's no difference?
> Could it be that it's actually first write that takes extra ref?
> cat is reading in 65536 byte chunks for me, awk only 1024.

Yes, there is no difference if I use "cat /proc/modules":

[root@skholman-m7 mnt]# awk '{print $1, $2, $3}' /proc/modules|sort > nfs
[root@skholman-m7 mnt]# grep sunrpc nfs
sunrpc 207591 29
[root@skholman-m7 mnt]# cat /proc/modules > temp
[root@skholman-m7 mnt]# awk '{print $1, $2, $3}' temp|sort > nfs
[root@skholman-m7 mnt]# grep sunrpc temp
sunrpc 207591 28 nfs,nfsd,lockd,nfs_acl,auth_rpcgss, Live 0x00000000101ec000
[root@skholman-m7 mnt]#

As for 1024. lsmod also reads /proc/modules in 1024 bytes chunks.

> 
> Regards,
> Jan
> 
>>
>>
>>
>>>
>>> But shouldn't the shell open the temp file the output is redirected to
>>> before it executes the command line anyway?
>>>
>>
>> --
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>>