cifs: check the timestamp for the cached dirent when deciding on revalidate

Improves directory metadata caching
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/cifs/inode.c

@@ -2193,6 +2193,8 @@ cifs_dentry_needs_reval(struct dentry *dentry)
 	struct inode *inode = d_inode(dentry);
 	struct cifsInodeInfo *cifs_i = CIFS_I(inode);
 	struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
+	struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);
+	struct cached_fid *cfid = NULL;
 
 	if (cifs_i->time == 0)
 		return true;
@@ -2203,6 +2205,16 @@ cifs_dentry_needs_reval(struct dentry *dentry)
 	if (!lookupCacheEnabled)
 		return true;
 
+	if (!open_cached_dir_by_dentry(tcon, dentry->d_parent, &cfid)) {
+		mutex_lock(&cfid->fid_mutex);
+		if (cfid->time && cifs_i->time > cfid->time) {
+			mutex_unlock(&cfid->fid_mutex);
+			close_cached_dir(cfid);
+			return false;
+		}
+		mutex_unlock(&cfid->fid_mutex);
+		close_cached_dir(cfid);
+	}
 	/*
 	 * depending on inode type, check if attribute caching disabled for
 	 * files or directories