hi,

> > > why do you always want to do the automatic removal for CREATE case?
> > > consider O_EXCL create on nfsv2.
> > > if you already have a negative cache entry,
> > > i guess you don't want to issue a remote call to recheck it.
> > > (or, at least, want to let the filesystem implementation make
> > > its decision about usefulness of the cache.)
> > > because current cache_lookup() silently removes the entry,
> > > you have no clean way to see the negative entry.
> 
> I definitely think the "no way to see" aspect is bad. I think there may 
> still be value in keeping the removal, but we definitely should let the fs 
> know there was/is an entry.

for a little better example...

even ufs can take advantages from (non-whiteout) negative entries
because, in that case, it doesn't need to search the entire directory
to check whether or not the entry exists already.

YAMAMOTO Takashi