Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754634Ab1FTNSY (ORCPT ); Mon, 20 Jun 2011 09:18:24 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:41776 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754215Ab1FTNSU (ORCPT ); Mon, 20 Jun 2011 09:18:20 -0400 Date: Mon, 20 Jun 2011 14:18:18 +0100 From: Al Viro To: David Howells Cc: linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [RFC] get_write_access()/deny_write_access() without inode->i_lock Message-ID: <20110620131818.GR11521@ZenIV.linux.org.uk> References: <20110619235147.GQ11521@ZenIV.linux.org.uk> <21839.1308574037@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21839.1308574037@redhat.com> 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: 756 Lines: 19 On Mon, Jun 20, 2011 at 01:47:17PM +0100, David Howells wrote: > Al Viro wrote: > > > + for (v = atomic_read(&inode->i_writecount); v >= 0; v = v1) { > > + v1 = atomic_cmpxchg(&inode->i_writecount, v, v + 1); > > + if (likely(v1 == v)) > > + return 0; > > + } > > You don't need to reissue the atomic_read(). atomic_cmpxchg() returns the > current value of the memory location. Just set v to v1 before going round the > loop again. That's precisely what that loop is doing... -- 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/