From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 04/19] fs: Implement lazy LRU updates for inodes. Date: Sat, 16 Oct 2010 20:47:10 -0400 Message-ID: <20101017004710.GC1614@infradead.org> References: <1287216853-17634-1-git-send-email-david@fromorbit.com> <1287216853-17634-5-git-send-email-david@fromorbit.com> <20101016092916.GA32197@amd> <20101016165930.GA20626@infradead.org> <20101016172924.GA3519@amd> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Dave Chinner , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Nick Piggin Return-path: Content-Disposition: inline In-Reply-To: <20101016172924.GA3519@amd> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Sun, Oct 17, 2010 at 04:29:24AM +1100, Nick Piggin wrote: > > I don't think the pointer check will work either. By the time we retake > > the lru lock the inode might already have been reaped through a call > > to invalidate_inodes. There's no way we can do anything with it after > > I don't think you're right. If we re take inode_lock, ensure it is on > the LRU, and call the can_unuse checks, there is no more problem than > the regular loop taking items from the LRU, AFAIKS. As long as we have the global inode lock it should indeed be safe. But once we have a separate lru lock (global or per-zone, with or without i_lock during the addition) there is nothing preventing the inode from getting reused and re-added to the lru in the meantime. Sure this is an extremly unlikely case, but there is no locking to prevent it once inode_lock is gone.