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NFS: allow close-to-open cache semantics to apply to root of NFS filesystem 

To obey NFS cache semantics, the client must verify the cached
attributes when a file is opened.  In most cases this is done by a call to
d_validate as one of the last steps in path_walk.

However for the root of a filesystem, d_validate is only ever called
on the mounted-on filesystem (except when the path ends '.' or '..').
So NFS has no chance to validate the attributes.

So, in nfs_opendir, we revalidate the attributes if the opened
directory is the mountpoint.  This may cause double-validation for "."
and ".." lookups, but that is better than missing regular /path/name
lookups completely.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Neil Brown 2010-08-10 10:20:05 -04:00 committed by Trond Myklebust
parent 669502ff31
commit f5a73672d1
1 changed files with 7 additions and 0 deletions
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7
fs/nfs/dir.c
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@ -140,6 +140,13 @@ nfs_opendir(struct inode *inode, struct file *filp)
/* Call generic open code in order to cache credentials */
res = nfs_open(inode, filp);
if (filp->f_path.dentry == filp->f_path.mnt->mnt_root) {
/* This is a mountpoint, so d_revalidate will never
* have been called, so we need to refresh the
* inode (for close-open consistency) ourselves.
*/
__nfs_revalidate_inode(NFS_SERVER(inode), inode);
}
return res;
}