NFSDv4: use export cache flushtime for changeid on V4ROOT objects.

If you change the set of filesystems that are exported, then
the contents of various directories in the NFSv4 pseudo-root
is likely to change.  However the change-id of those
directories is currently tied to the underlying directory,
so the client may not see the changes in a timely fashion.

This patch changes the change-id number to be derived from the
"flush_time" of the export cache.  Whenever any changes are
made to the set of exported filesystems, this flush_time is
updated.  The result is that clients see changes to the set
of exported filesystems much more quickly, often immediately.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 3cc1907559586094a9d5fae0174dac72926fc379..7e4df80456fff3462fa4ec5733e943102863a7aa 100644 (file)
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -1966,9 +1966,13 @@ nfsd4_decode_compound(struct nfsd4_compoundargs *argp)
        DECODE_TAIL;
 }
 
-static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode)
+static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
+                            struct svc_export *exp)
 {
-       if (IS_I_VERSION(inode)) {
+       if (exp->ex_flags & NFSEXP_V4ROOT) {
+               *p++ = cpu_to_be32(convert_to_wallclock(exp->cd->flush_time));
+               *p++ = 0;
+       } else if (IS_I_VERSION(inode)) {
                p = xdr_encode_hyper(p, inode->i_version);
        } else {
                *p++ = cpu_to_be32(stat->ctime.tv_sec);
@@ -2493,7 +2497,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
                p = xdr_reserve_space(xdr, 8);
                if (!p)
                        goto out_resource;
-               p = encode_change(p, &stat, d_inode(dentry));
+               p = encode_change(p, &stat, d_inode(dentry), exp);
        }
        if (bmval0 & FATTR4_WORD0_SIZE) {
                p = xdr_reserve_space(xdr, 8);