On Tue, Feb 11, 2025 at 06:01:21PM +0000, Viacheslav Dubeyko wrote:
> After some considerations, I believe we can follow such simple logic.
> Correct me if I will be wrong here. The ceph_lookup() method's responsibility is
> to "look up a single dir entry". It sounds for me that if we have positive
> dentry,
> then it doesn't make sense to call the ceph_lookup(). And if ceph_lookup() has
> been
> called for the positive dentry, then something wrong is happening.
VFS never calls it that way; ceph itself might, if ceph_handle_notrace_create()
is called with positive dentry.
> But all this logic is not about negative dentry, it's about local check
> before sending request to MDS server. So, I think we need to change the logic
> in likewise way:
>
> if (<we can check locally>) {
> <do check locally>
> if (-ENOENT)
> return NULL;
> } else {
> <send request to MDS server>
> }
>
> Am I right here? :) Let me change the logic in this way and to test it.
First of all, returning NULL does *not* mean "it's negative"; d_add(dentry, NULL)
does that. What would "we can check locally" be? AFAICS, the checks in
__ceph_dir_is_complete() and near it are doing just that...
The really unpleasant question is whether ceph_handle_notrace_create() could
end up feeding an already-positive dentry to direct call of ceph_lookup()...
