On Tue, May 7, 2019 at 12:16 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> Negative ->d_lockref.count are used for "lockref is dead"...
We can change that to just -1, can't we? It's equally easy to test for.
Those aren't supposed to be incremented anyway, which is the whole point.
But we could do what the page refs also did: consider refcounts in the
"small negative range" to be very special, because they are either
critically close to an overflow, or they are actually a sign of a
fatal underflow due to some bug. And make one of those be the dead
marker.
(See page_ref_zero_or_close_to_overflow() for the particular critical
range check for the page ref)
Linus
