atomic_open(): lift the call of may_open() into do_last()

there we'll be able to merge it with its counterparts in other
cases, and there's no reason to do it before the parent has
been unlocked
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/namei.c

@@ -2949,23 +2949,12 @@ static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
 	d_lookup_done(dentry);
 	if (!error) {
 		if (file->f_mode & FMODE_OPENED) {
-			int acc_mode = op->acc_mode;
 			if (unlikely(dentry != file->f_path.dentry)) {
 				dput(dentry);
 				dentry = dget(file->f_path.dentry);
 			}
-			/*
-			 * We didn't have the inode before the open, so check open
-			 * permission here.
-			 */
-			if (file->f_mode & FMODE_CREATED) {
-				WARN_ON(!(open_flag & O_CREAT));
+			if (file->f_mode & FMODE_CREATED)
 				fsnotify_create(dir, dentry);
-				acc_mode = 0;
-			}
-			error = may_open(&file->f_path, acc_mode, open_flag);
-			if (WARN_ON(error > 0))
-				error = -EINVAL;
 		} else if (WARN_ON(file->f_path.dentry == DENTRY_NOT_SET)) {
 			error = -EIO;
 		} else {
@@ -3208,12 +3197,19 @@ static const char *do_last(struct nameidata *nd,
 	}
 
 	if (file->f_mode & FMODE_OPENED) {
-		if ((file->f_mode & FMODE_CREATED) ||
-		    !S_ISREG(file_inode(file)->i_mode))
+		if (file->f_mode & FMODE_CREATED) {
+			open_flag &= ~O_TRUNC;
+			will_truncate = false;
+			acc_mode = 0;
+		} else if (!S_ISREG(file_inode(file)->i_mode))
 			will_truncate = false;
 
 		audit_inode(nd->name, file->f_path.dentry, 0);
-		dput(dentry);
+		dput(nd->path.dentry);
+		nd->path.dentry = dentry;
+		error = may_open(&nd->path, acc_mode, open_flag);
+		if (error)
+			goto out;
 		goto opened;
 	}