On Tue, Sep 10, 2013 at 05:01:23PM -0700, Linus Torvalds wrote: > On Tue, Sep 10, 2013 at 4:53 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > list_lru_add() can fail if it's already on the list; leaving the counter > > alone should've been conditional on that, setting the flag - no. Said > > that, it probably should be WARN_ON(!...); this_cpu_inc(); ... |= ...; > > That WARN_ON_(!..) might indeed be better (maybe just WARN_ON_ONCE()).. > > That DCACHE_LRU_LIST bit needs to be coherent with "the dentry->d_lru > entry is on _some_ list" (whether it's the dentry one or the shrinker > one), so if that list_lru_add() ever fails, that would be a sign of > badness. > > And that whole function is very performance-critical, to the point > where we not only don't want to call down to list_lry_add(), we don't > even want to touch the d_lru list entry itself to even _look_ if it's > empty or not, because that will take a cache miss. Which was obviously > the whole reason for that DCACHE_LRU_LIST bit existing... Guys, I'm about to be out of the office for 4-5 days, so this is real bad timing for me. When I get back I'll put some effort into validating that everything still works properly and performs as expected. Cheers, Dave. -- Dave Chinner dchinner@xxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
