coda: avoid flagging NULL inodes

Somehow we hit a negative dentry in coda_rename even after checking with
d_really_is_positive.  Maybe something raced and turned the new_dentry
negative while we were fixing up directory link counts.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jan Harkes <[email protected]>
Cc: Alex Shi <[email protected]>
Cc: Jing Yangyang <[email protected]>
Cc: Xin Tan <[email protected]>
Cc: Xiyu Yang <[email protected]>
Cc: Zeal Robot <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/coda/coda_linux.h

@@ -83,6 +83,9 @@ static __inline__ void coda_flag_inode(struct inode *inode, int flag)
 {
 	struct coda_inode_info *cii = ITOC(inode);
 
+	if (!inode)
+		return;
+
 	spin_lock(&cii->c_lock);
 	cii->c_flags |= flag;
 	spin_unlock(&cii->c_lock);