[fuse] Unexpectedly large number of getattr() and lookup requests

[Nikolaus Rath <Nikolaus@rath.org>]

Hello,

I am seeing an unexpectedly large number of getattr() and lookup()
requests being sent to userspace fuse. I am setting a very large
attr_timeout and entry_timeout, so I would have expected that the
maximum number of getattr() and lookup() requests is capped by the
number of distinct files in the filesystem plus the number of forget
requests.

However, actual numbers are much higher. For example, when running tests
on a filesystem with 2960 directory entries, I am getting scenarios
with 203447 lookup requests, 12970 getattr requests, and zero forget
requests.

Did I misunderstand something about how dentry and attribute caching
works?

Thanks,
-Nikolaus
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