How to best return errors on follow_link

How to best return errors on follow_link

[Steve French]

Jeff noticed a problem with the error handling in cifs_follow_link
that brought up a question about how follow_link is supposed to be
handling errors.  His change has a sideeffect of now returning NULL
instead of an  ENOMEM on memory allocation errors in cifs_follow_link.

The caller of follow_link in the VFS  (__do_follow_link) seems to
expect errors to be returned (see below piece of fs/namei.c) not a
NULL ptr:

	cookie = dentry->d_inode->i_op->follow_link(dentry, nd);
	error = PTR_ERR(cookie);
	if (!IS_ERR(cookie)) {
		char *s = nd_get_link(nd);
		error = 0;
		if (s)
			error = __vfs_follow_link(nd, s);
		if (dentry->d_inode->i_op->put_link)
			dentry->d_inode->i_op->put_link(dentry, nd, cookie);
	}
	path_put(path);
	return error;

Some file systems rather than returning an error to the caller will
call nd_set_link while will set:         nd->saved_names[nd->depth] =
to the error;


Is it ok to return errors on follow_link - seems strange to return
them indicectly via set_link?
-- 
Thanks,

Steve

Re: How to best return errors on follow_link

[Steve French]

On Mon, May 18, 2009 at 12:30 PM, Steve French <smfrench@gmail.com> wrote:
> Jeff noticed a problem with the error handling in cifs_follow_link
> that brought up a question about how follow_link is supposed to be
> handling errors.  His change has a sideeffect of now
> Is it ok to return errors on follow_link - seems strange to return
> them indicectly via set_link?

Sorry about the typo indecently was supposed to be "indirectly"
(return errors on set_link)    :)



-- 
Thanks,

Steve
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