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Date: Wed, 11 Sep 2013 10:39:05 +1000 From: Dave Chinner <dchinner@...hat.com> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Al Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Stephen Rothwell <sfr@...b.auug.org.au>, linux-next <linux-next@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Glauber Costa <glommer@...nvz.org> Subject: Re: linux-next: manual merge of the akpm tree with Linus' tree 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@...iv.linux.org.uk> 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@...hat.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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