On Fri, 29 Aug 2025 at 09:18, Steven Rostedt [off-list ref] wrote:

Basically what I need is that every time I add a file/hash mapping to the
hashtable, I really need a callback to know when that file goes away. And
then I can remove it from the hash table, so that the next time that hash is
added, it will trigger another "print the file associated with this hash".

That works, but why would you care?

Why don't you just register the hash value and NOT CARE.

Leave it all to later when the trace gets analyzed.

Leave it be. The normal situation is presumably going to be that
millions of stack traces will be generated, and nobody will even look
at them.

My question now is, is there a callback that can be registered by the
file_cache to know when the vma or the file change?

No. And what's the point? I just told you that unmap doesn't matter.
All that matters is mmap.

Don't try to "reuse" hashes. Just treat them as opaque numbers.

             Linus