Re: [PATCH 02/11] vfs: More precise tests in d_invalidate

Linus Torvalds [off-list ref] writes:

On Sat, Feb 15, 2014 at 3:23 PM, Eric W. Biederman
[off-list ref] wrote:

quoted

Except that today d_invalidate drops the dcache lock and
calls shrink_dcache_parent.  Which gets you into exactly the same
complex "walk parents and check all siblings" code.

Hmm. It only does that for directories that have sub-entries, though.

I think you may care just about directories (because that's what your
series is about), but d_invalidate() is used for other cases too,
notably d_revalidate() (ie things like stale NFS lookups of normal
files).

That said, I'll have to think about this more. If d_subdir is empty, I
guess d_walk() will be fairly cheap. It's very different, but maybe
not as disastrous as I thought.

Thank you for taking the time to look.

It is also very true that I have been mostly focusing on the semantics
and correctness rather than on the performance of these changes.

I did keep a weather eye on the performance impact of these changes
though and as long as we can stand a slow down in the rare case where
mount points are present my changes should be fine.

Eric