eventfs: Fix events beyond NAME_MAX blocking tasks

Eventfs uses simple_lookup(), however, it will fail if the name of the entry is beyond NAME_MAX length. When this error is encountered, eventfs still tries to create dentries instead of skipping the dentry creation. When the dentry is attempted to be created in this state d_wait_lookup() will loop forever, waiting for the lookup to be removed.

Fix eventfs to return the error in simple_lookup() back to the caller instead of continuing to try to create the dentry.

---
Please note the fixes tag is the first add of simple_lookup logic, there have been other changes beyond that may be a better fit to targetting.

 fs/tracefs/event_inode.c | 4 ++++
 1 file changed, 4 insertions(+)

index f8a594a50ae6..d2c06ba26db4 100644
@@ -561,6 +561,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
 		if (strcmp(ei_child->name, name) != 0)
 			continue;
 		ret = simple_lookup(dir, dentry, flags);
+		if (IS_ERR(ret))
+			goto out;
 		create_dir_dentry(ei, ei_child, ei_dentry, true);
 		created = true;
 		break;

@@ -583,6 +585,8 @@ static struct dentry *eventfs_root_lookup(struct inode *dir,
 			if (r <= 0)
 				continue;
 			ret = simple_lookup(dir, dentry, flags);
+			if (IS_ERR(ret))
+				goto out;
 			create_file_dentry(ei, i, ei_dentry, name, mode, cdata,
 					   fops, true);
 			break;

2.34.1