I was trying to do something like this:
filter="events/writeback/writeback_mark_inode_dirty/filter"
echo "(flags & 2048) && ((state & 2048) == 0)" > $filter
... but that doesn't work.
This works:
echo "flags & 2048" > $filter
But the problem is this:
echo "(state & 2048) == 0" > $filter
The simplest patch to add this would be add a new filter_ops so we
could do this:
echo "(state !& 2048)" > $filter
... but that's pretty ugly. But adding more general expression
parsing in the ftrace event filter code would be non-trivial, and if
we start trying to make things like "!(state & 2048)" or "(state &
2048) == 0", then at some point some crazy person might request
supporting something like this: "(state ^ flags) == 2048". :-)
So I guess the main question I want to ask is your opinion about
whether a patch that adds support for the operator "!&" is too ugly to
live?
Thanks,
- Ted
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