From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753325AbdBUQEQ (ORCPT ); Tue, 21 Feb 2017 11:04:16 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:40846 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751867AbdBUQEI (ORCPT ); Tue, 21 Feb 2017 11:04:08 -0500 Date: Tue, 21 Feb 2017 17:04:08 +0100 From: Peter Zijlstra To: Elena Reshetova Cc: linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, gregkh@linuxfoundation.org, darrick.wong@oracle.com, Hans Liljestrand , Kees Cook , David Windsor Subject: Re: [PATCH 2/7] fs, xfs: convert xfs_buf.b_hold and xfs_buf.b_lru_ref from atomic_t to refcount_t Message-ID: <20170221160408.GJ6515@twins.programming.kicks-ass.net> References: <1487692147-17066-1-git-send-email-elena.reshetova@intel.com> <1487692147-17066-3-git-send-email-elena.reshetova@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1487692147-17066-3-git-send-email-elena.reshetova@intel.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 21, 2017 at 05:49:02PM +0200, Elena Reshetova wrote: > @@ -1684,10 +1684,11 @@ xfs_buftarg_isolate( > * zero. If the value is already zero, we need to reclaim the > * buffer, otherwise it gets another trip through the LRU. > */ > - if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) { > + if (!refcount_read(&bp->b_lru_ref)) { > spin_unlock(&bp->b_lock); > return LRU_ROTATE; > } > + refcount_dec_and_test(&bp->b_lru_ref); > > bp->b_state |= XFS_BSTATE_DISPOSE; > list_lru_isolate_move(lru, item, dispose); This should never have passed testing.. refcount_dec_and_test() has a __must_check. Furthermore the above seems to suggest thingies can live with a 0 refcount, so a straight conversion cannot work.