Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932786Ab3CVGJ7 (ORCPT ); Fri, 22 Mar 2013 02:09:59 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:40543 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754012Ab3CVGJ6 (ORCPT ); Fri, 22 Mar 2013 02:09:58 -0400 Date: Fri, 22 Mar 2013 06:09:53 +0000 From: Al Viro To: Linus Torvalds Cc: Dave Jones , Linux Kernel , "Eric W. Biederman" Subject: Re: [CFT] Re: VFS deadlock ? Message-ID: <20130322060953.GN21522@ZenIV.linux.org.uk> References: <20130322001257.GH21522@ZenIV.linux.org.uk> <20130322012208.GJ21522@ZenIV.linux.org.uk> <20130322014037.GK21522@ZenIV.linux.org.uk> <20130322043715.GL21522@ZenIV.linux.org.uk> <20130322051817.GM21522@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1308 Lines: 24 On Thu, Mar 21, 2013 at 10:33:27PM -0700, Linus Torvalds wrote: > Ok, that's kind of ugly, but shouldn't be a correctness issue. It > should still work - just cycle through inodes quite aggressivelydue to > no longer re-using them - so I suspect Dave could test it (with the > extra line removed I pointed out just a moment ago). > > And I wonder how big of a deal the aggressive dentry deletion is. > Maybe it's even ok to allocate/free the inodes all the time. The whole > "get the inode hash lock and look it up there" can't be all that > wonderful either. It takes the inode->i_lock for each entry it finds > on the hash list, which looks horrible. I suspect our slab allocator > isn't much worse than that, although the RCU freeing of the inodes > could end up being problematic. Hell knows... At the very least, I'd expect /proc/self to be fairly hot. During the boot time - /proc/mounts, /proc/filesystems, /proc/cmdline... Dunno. Would be interesting to slap a printk into proc_lookup_de() and see how much (and what) does it hit on a busy system... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/