ceph: Propagate dentry down to inode_change_ok()

To avoid clearing of capabilities or security related extended
attributes too early, inode_change_ok() will need to take dentry instead
of inode. ceph_setattr() has the dentry easily available but
__ceph_setattr() is also called from ceph_set_acl() where dentry is not
easily available. Luckily that call path does not need inode_change_ok()
to be called anyway. So reorganize functions a bit so that
inode_change_ok() is called only from paths where dentry is available.

Reviewed-by: Christoph Hellwig <[e-mail]>
Acked-by: Jeff Layton <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/ceph/acl.c

···
 			goto out_free;
 	}
 
+	if (ceph_snap(inode) != CEPH_NOSNAP) {
+		ret = -EROFS;
+		goto out_free;
+	}
+
 	if (new_mode != old_mode) {
 		newattrs.ia_mode = new_mode;
 		newattrs.ia_valid = ATTR_MODE;

fs/ceph/inode.c

···
 	int inode_dirty_flags = 0;
 	bool lock_snap_rwsem = false;
 
-	if (ceph_snap(inode) != CEPH_NOSNAP)
-		return -EROFS;
-
-	err = inode_change_ok(inode, attr);
-	if (err != 0)
-		return err;
-
 	prealloc_cf = ceph_alloc_cap_flush();
 	if (!prealloc_cf)
 		return -ENOMEM;
···
  */
 int ceph_setattr(struct dentry *dentry, struct iattr *attr)
 {
-	return __ceph_setattr(d_inode(dentry), attr);
+	struct inode *inode = d_inode(dentry);
+	int err;
+
+	if (ceph_snap(inode) != CEPH_NOSNAP)
+		return -EROFS;
+
+	err = inode_change_ok(inode, attr);
+	if (err != 0)
+		return err;
+
+	return __ceph_setattr(inode, attr);
 }
 
 /*