Ok, so this is a delegation bug. I think you're rigth Bruce, I cannot
see the bug if I just modify the file with vi.
I'll try your delegation patch ASAP.
Thanks,
Diego
On Wed 05 Sep 2012 07:21:58 PM CEST, J. Bruce Fields wrote:
On Wed, Sep 05, 2012 at 02:49:18PM +0000, Myklebust, Trond wrote:
On Wed, 2012-09-05 at 14:40 +0200, Diego Moreno wrote:
Hello everyone,
Performing some attribute caching tests I think I found some
inconsistencies between nfsv3 and nfsv4. Running a kernel based on
rhel6.3 (2.6.32-279.el6.x86_64) I found nfsv4 doesn't manage a file
modified on the server side (even with the noac mount option) while
nfsv3 does.
My test will be modifying a file every second on the server mount point:
[root@nfs ~]# FILE=/tmp/nfs_server/myfile ; while true ; do sleep 1 ;
sed -i 's/text1/text2/g' $FILE ; cat $FILE ; sleep 1; sed -i
's/text2/text1/g' $FILE ; cat $FILE ; done
text2
text1
text2
text1
text2
(and so on...)
Meanwhile, the client (which BTW is the same machine) will read the file
every second :
With NFSv4:
[root@nfs ~]# mount -o noac,vers=4 nfs:/tmp/nfs_server/ /tmp/nfs_client/
[root@nfs ~]# for i in 1 2 3 4 5 ; do cat /tmp/nfs_client/myfile; sleep
1 ; done
text2
text1
text1
text1
text1
With NFSv3:
[root@nfs ~]# mount -o noac,vers=3 nfs:/tmp/nfs_server/ /tmp/nfs_client/
[root@nfs ~]# for i in 1 2 3 4 5 ; do cat /tmp/nfs_client/myfile; sleep
1 ; done
text1
text2
text1
text2
text1
I can see in the tcpdump traces how the new change attribute and the
FATTR4_TIME_MODIFY attributes are well received but it's as if the nfs
client were ignoring these changes. I've been searching in the NFS list
but I didn't find anything similar. Is this a bug or just a normal
behavior? Sorry if it has been already pointed out.
]If you can reproduce the same issues on the upstream kernel, then it is
on topic for this list, otherwise it is a question for Red Hat.
I believe sed -i is actually doing a rename not a file modification. So
the problem is likely another symptom of the bug that delegations aren't
revoked on rename/link/unlink. Hoping to post the latest draft of
patches to fix that later today.
--b.
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