On Wed, Dec 17, 2008 at 01:36:12PM +0800, lioupayphone wrote:
> Hello, everyone.
>
> fsid in /etc/exports was used for identifying a file system. if a file system which exported 2 directories, it seems that we should tag the two export entries with same fsid.
>
> eg
> on one machine (server 10.10.37.147, Centos5.2 with linux2.6.18):
>
> #mkfs.ext3 /dev/sdc; mount /dev/sdc /mnt/;mkdir -p /mnt/dir1 /mnt/dir2; touch /mnt/dir1/wall-e /mnt/dir2/eva;
> #echo "/mnt/dir1 *(rw,async,root_squash,fsid=2)" > /etc/exports
> #echo "/mnt/dir2 *(rw,async,root_squash,fsid=2)" >> /etc/exports
That's an odd thing to do; could you explain what you're trying to
accomplish?
--b.
> #service nfs start && exportfs -r
>
> on another machine (client 10.10.37.154):
> #mount 10.10.37.147:/mnt/dir1 /mnt/1/ && mount 10.10.37.147:/mnt/dir2 /mnt/2/
>
> i am puzzled: on the client (10.10.37.154), i found both "/mnt/1/" and "/mnt/2/" have the same child ---- "wall-e".
>
> so i browsed the code of 2.6.18 and found: exp_export(), fs/nfsd/export.c . i have taged a comment on this code listed below. please give me some suggestions. thx.
>
> /*
> * Export a file system.
> */
> int
> exp_export(struct nfsctl_export *nxp)
> {
> svc_client *clp;
> struct svc_export *exp = NULL;
> struct svc_export new;
> struct svc_expkey *fsid_key = NULL;
> struct nameidata nd;
> int err;
>
> /* Consistency check */
> err = -EINVAL;
> if (!exp_verify_string(nxp->ex_path, NFS_MAXPATHLEN) ||
> !exp_verify_string(nxp->ex_client, NFSCLNT_IDMAX))
> goto out;
>
> dprintk("exp_export called for %s:%s (%x/%ld fl %x).\n",
> nxp->ex_client, nxp->ex_path,
> (unsigned)nxp->ex_dev, (long)nxp->ex_ino,
> nxp->ex_flags);
>
> /* Try to lock the export table for update */
> exp_writelock();
>
> /* Look up client info */
> if (!(clp = auth_domain_find(nxp->ex_client)))
> goto out_unlock;
>
>
> /* Look up the dentry */
> err = path_lookup(nxp->ex_path, 0, &nd);
> if (err)
> goto out_unlock;
> err = -EINVAL;
>
> exp = exp_get_by_name(clp, nd.mnt, nd.dentry, NULL);
>
> /* must make sure there won't be an ex_fsid clash */
> if ((nxp->ex_flags & NFSEXP_FSID) &&
> (fsid_key = exp_get_fsid_key(clp, nxp->ex_dev)) &&
> !IS_ERR(fsid_key) &&
> fsid_key->ek_mnt &&
> /*
> * --> HERE. "nd.mnt of "/mnt/dir1" and "/mnt/dir2" are same, but nd.dentry not.
> * "(fsid_key->ek_mnt != nd.mnt || fsid_key->ek_dentry != nd.dentry)" will be 1 in such
> * a situation. but they are different exp-entries in "/var/lib/nfs/etab"
> * it should be "(fsid_key->ek_dentry != nd.dentry || fsid_key->ek_mnt != nd.mnt)" ??
> */
> (fsid_key->ek_mnt != nd.mnt || fsid_key->ek_dentry != nd.dentry) )
> goto finish;
>
> if (exp) {
> /* just a flags/id/fsid update */
>
> exp_fsid_unhash(exp);
> exp->ex_flags = nxp->ex_flags;
> exp->ex_anon_uid = nxp->ex_anon_uid;
> exp->ex_anon_gid = nxp->ex_anon_gid;
> exp->ex_fsid = nxp->ex_dev;
>
> err = exp_fsid_hash(clp, exp);
> goto finish;
> }
>
> err = check_export(nd.dentry->d_inode, nxp->ex_flags);
> if (err) goto finish;
>
> err = -ENOMEM;
>
> dprintk("nfsd: creating export entry %p for client %p\n", exp, clp);
>
> new.h.expiry_time = NEVER;
> new.h.flags = 0;
> new.ex_client = clp;
> new.ex_mnt = nd.mnt;
> new.ex_dentry = nd.dentry;
> new.ex_flags = nxp->ex_flags;
> new.ex_anon_uid = nxp->ex_anon_uid;
> new.ex_anon_gid = nxp->ex_anon_gid;
> new.ex_fsid = nxp->ex_dev;
>
> exp = svc_export_lookup(&new);
> if (exp)
> exp = svc_export_update(&new, exp);
>
> if (!exp)
> goto finish;
>
> if (exp_hash(clp, exp) ||
> exp_fsid_hash(clp, exp)) {
> /* failed to create at least one index */
> exp_do_unexport(exp);
> cache_flush();
> err = -ENOMEM;
> }
>
> finish:
> if (exp)
> exp_put(exp);
> if (fsid_key && !IS_ERR(fsid_key))
> cache_put(&fsid_key->h, &svc_expkey_cache);
> if (clp)
> auth_domain_put(clp);
> path_release(&nd);
> out_unlock:
> exp_writeunlock();
> out:
> return err;
> }
>
>
>
> Best Regards!
> lioupayphone
>
>
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