Description of problem:
Specific NFS server setup results on BUG on linux nfs client:
the configuration is the following:
tc27.qa.sw.ru -- NFS server (FC8)
ts27.qa.sw.ru -- NFS client (RHEL5)
Server configuration is the following:
[root@tc27 proc]# cat /etc/exports
[root@tc27 proc]# cat /proc/mounts
/dev/mapper/vzvg-vz /nfs_share ext3 rw,data=ordered 0 0
/dev/sda1 /nfs_share/boo ext3 rw,data=ordered 0 0
Issue can be reproduced by the following script on CLIENT SIDE:
[root@ts27 ~]# cat sub-mounts.sh
echo 65535 > /proc/sys/sunrpc/nfs_debug
echo 65535 > /proc/sys/sunrpc/rpc_debug
stat -f /mnt/nfs/ | grep -q 'Type: nfs' ||
mount -v -t nfs tc27:/nfs_share /mnt/nfs -o vers=3,tcp,hard,nointr
grep nfs /proc/mounts
This BUG_ON happens due to improper behavior of rpc.mountd process on the nfs server. This is proven by the following file on the server:
[root@tc27 proc]# cat /proc/net/rpc/nfsd.fh/content
#domain fsidtype fsid [path]
*,ts27 0 0x0000fd0000000002 /nfs_share
*,ts27 0 0x0100080000000002 /nfs_share
As you can see it contains /nfs_share instead of /nfs_share/boo for 0x0100080000000002 fsid.
Version-Release number of selected component (if applicable):
BUG_ON on client side on nfs submount lookup because of incorrect content of
correct content of /proc/net/rpc/nfsd.fh/content file
The patch posted to the linux-nfs mailing list:
Unfortunately, BUG_ON(IS_ROOT(dentry)) can happen inside
nfs_follow_mountpoint with NFS running Fedora 8 using a
So, the situation should be handled on NFS client gracefully.
Signed-off-by: Denis V. Lunev <firstname.lastname@example.org>
CC: Trond Myklebust <Trond.Myklebust@netapp.com>
CC: J. Bruce Fields <email@example.com>
fs/nfs/namespace.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)
diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 66df08d..4f11c13 100644
@@ -105,7 +105,10 @@ static void * nfs_follow_mountpoint(struct dentry *dentry, struct nameidata *nd)
+ err = -ESTALE;
+ if (IS_ROOT(dentry))
+ goto out_err;
dprintk("%s: enter\n", __func__);
nd->path.dentry = dget(dentry);
I've created a separate bug for RHEL5 NFS client panic
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