nfsd: fix NFSv4 time_delta attribute
Currently we return the worst-case value of 1 second in the time delta
attribute. That's not terribly useful. Instead, return a value
calculated from the time granularity supported by the filesystem and the
system clock.
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index a96843c..4161031 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2006,6 +2006,31 @@ static __be32 *encode_change(__be32 *p, struct kstat *stat, struct inode *inode,
return p;
}
+/*
+ * ctime (in NFSv4, time_metadata) is not writeable, and the client
+ * doesn't really care what resolution could theoretically be stored by
+ * the filesystem.
+ *
+ * The client cares how close together changes can be while still
+ * guaranteeing ctime changes. For most filesystems (which have
+ * timestamps with nanosecond fields) that is limited by the resolution
+ * of the time returned from current_time() (which I'm assuming to be
+ * 1/HZ).
+ */
+static __be32 *encode_time_delta(__be32 *p, struct inode *inode)
+{
+ struct timespec ts;
+ u32 ns;
+
+ ns = max_t(u32, NSEC_PER_SEC/HZ, inode->i_sb->s_time_gran);
+ ts = ns_to_timespec(ns);
+
+ p = xdr_encode_hyper(p, ts.tv_sec);
+ *p++ = cpu_to_be32(ts.tv_nsec);
+
+ return p;
+}
+
static __be32 *encode_cinfo(__be32 *p, struct nfsd4_change_info *c)
{
*p++ = cpu_to_be32(c->atomic);
@@ -2797,9 +2822,7 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
p = xdr_reserve_space(xdr, 12);
if (!p)
goto out_resource;
- *p++ = cpu_to_be32(0);
- *p++ = cpu_to_be32(1);
- *p++ = cpu_to_be32(0);
+ p = encode_time_delta(p, d_inode(dentry));
}
if (bmval1 & FATTR4_WORD1_TIME_METADATA) {
p = xdr_reserve_space(xdr, 12);