nfs mounting operation

nfs mounting operation

[Mohit Katiyar]

Hi all,

I am new to the NFS filesystem. When we perfrom a nfs mount the
nfs_getattr function is called. I would like to know why this getattr
function is called and from which function in the vfs layer. I think
it comes from vfs_stat_fd function but what are the parameters passed
to it for calling get_attribute. Basically whose attributes are being
searched??
The same case with unmounting operation. why this getattr function is
called and from where in vfs layer it is invoked?
I am using linux-2.6.15.

TIA
Mohit Katiyar

Re: nfs mounting operation

[Peter Staubach]

Mohit Katiyar wrote:
> Hi all,
>
> I am new to the NFS filesystem. When we perfrom a nfs mount the
> nfs_getattr function is called. I would like to know why this getattr
> function is called and from which function in the vfs layer. I think
> it comes from vfs_stat_fd function but what are the parameters passed
> to it for calling get_attribute. Basically whose attributes are being
> searched??
> The same case with unmounting operation. why this getattr function is
> called and from where in vfs layer it is invoked?
> I am using linux-2.6.15. 

The over the wire GETATTR function is used during mounting to get the
initial set of attributes for the root of the mounted file system.

 From time to time, GETATTR is also used to validate the attributes and
cached resources associated with entities on the mounted file system.

        ps

Re: nfs mounting operation

[Mohit Katiyar]

Hi
Thanks for the reply.
But i am really confused about the nfs superblock and root directory
maintainance.
For example
If we mount two partition as shown below

mount -t nfs host1:/export/dir1 /mnt/dir1/
mount -t nfs host2:/export/dir2 /mnt/dir2/

Then will there be two nfs superbocks created one per each mount?
If not and if there is only one nfs superblock then s_root entry of
the nfs superbolck will point to which root directory(of the first or
second mount).



On 9/28/06, Peter Staubach <staubach@redhat.com> wrote:
> Mohit Katiyar wrote:
> > Hi all,
> >
> > I am new to the NFS filesystem. When we perfrom a nfs mount the
> > nfs_getattr function is called. I would like to know why this getattr
> > function is called and from which function in the vfs layer. I think
> > it comes from vfs_stat_fd function but what are the parameters passed
> > to it for calling get_attribute. Basically whose attributes are being
> > searched??
> > The same case with unmounting operation. why this getattr function is
> > called and from where in vfs layer it is invoked?
> > I am using linux-2.6.15.
>
> The over the wire GETATTR function is used during mounting to get the
> initial set of attributes for the root of the mounted file system.
>
>  From time to time, GETATTR is also used to validate the attributes and
> cached resources associated with entities on the mounted file system.
>
>         ps
>

Re: nfs mounting operation

[Peter Staubach]

Mohit Katiyar wrote:
> Hi
> Thanks for the reply.
> But i am really confused about the nfs superblock and root directory
> maintainance.
> For example
> If we mount two partition as shown below
>
> mount -t nfs host1:/export/dir1 /mnt/dir1/
> mount -t nfs host2:/export/dir2 /mnt/dir2/
>
> Then will there be two nfs superbocks created one per each mount?
> If not and if there is only one nfs superblock then s_root entry of
> the nfs superbolck will point to which root directory(of the first or
> second mount). 

There will be two superblocks created, one per mount, assuming that
host1 and host2 are different systems.

I would suggest studying the code at this point.

       ps