On Fri, Apr 11, 2025 at 04:59:11PM +0100, David Howells wrote:
Jarkko Sakkinen jarkko@kernel.org wrote:
- spin_lock_irqsave(&key_graveyard_lock, flags);
- list_splice_init(&key_graveyard, &graveyard);
- spin_unlock_irqrestore(&key_graveyard_lock, flags);
I would wrap this bit in a check to see if key_graveyard is empty so that we can avoid disabling irqs and taking the lock if the graveyard is empty.
Can do, and does make sense.
if (!refcount_inc_not_zero(&key->usage)) {Sorry, but eww. You're going to wangle the refcount twice on every key on the system every time the gc does a pass. Further, in some cases inc_not_zero is not the fastest op in the world.
One could alternatively "test_bit(KEY_FLAG_FINAL_PUT, &key->flags)) && !refcount_inc_not_zero(&key->usage))" without mb() on either side and set_bit() could be at the beginning of key_put().
Race at worst would be an extra refcount_inc_not_zero() but not often.
spin_lock_irqsave(&key_graveyard_lock, flags);list_add_tail(&key->graveyard_link, &key_graveyard);spin_unlock_irqrestore(&key_graveyard_lock, flags); schedule_work(&key_gc_work);This is going to enable and disable interrupts twice and that can be expensive, depending on the arch. I wonder if it would be better to do:
local_irq_save(flags); spin_lock(&key_graveyard_lock); list_add_tail(&key->graveyard_link, &key_graveyard); spin_unlock(&key_graveyard_lock); schedule_work(&key_gc_work); local_irq_restore(flags);
I like this but shouldn't this also comprehend the quota update before (just asking for completeness sake)?
David
BR, Jarkko