On Sat, Apr 12, 2025 at 04:30:24AM +0300, Jarkko Sakkinen wrote:
On Fri, Apr 11, 2025 at 11:37:25PM +0300, Jarkko Sakkinen wrote:
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
Refactoring the changes to key_put() would be (draft):
I'll post a fresh patch set later :-) Deeply realized how this does not make sense as it is. So yeah, it'll be a patch set.
One change that would IMHO make sense would be
diff --git a/security/keys/key.c b/security/keys/key.c index 7198cd2ac3a3..aecbd624612d 100644 --- a/security/keys/key.c +++ b/security/keys/key.c @@ -656,10 +656,12 @@ void key_put(struct key *key) spin_lock_irqsave(&key->user->lock, flags); key->user->qnkeys--; key->user->qnbytes -= key->quotalen; + set_bit(KEY_FLAG_FINAL_PUT, &key->flags); spin_unlock_irqrestore(&key->user->lock, flags); + } else { + set_bit(KEY_FLAG_FINAL_PUT, &key->flags); + smp_mb(); /* key->user before FINAL_PUT set. */ } - smp_mb(); /* key->user before FINAL_PUT set. */ - set_bit(KEY_FLAG_FINAL_PUT, &key->flags); schedule_work(&key_gc_work); } }
I did not see anything obvious that would endanger anything and reduces the number of smp_mb()'s. This is just on top of mainline ...
BR, Jarkko