Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756809AbaBFRES (ORCPT ); Thu, 6 Feb 2014 12:04:18 -0500 Received: from fieldses.org ([174.143.236.118]:49264 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756793AbaBFREP (ORCPT ); Thu, 6 Feb 2014 12:04:15 -0500 Date: Thu, 6 Feb 2014 12:03:48 -0500 From: "J. Bruce Fields" To: Al Viro Cc: Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, Miklos Szeredi , Harshula , hfuchi@redhat.com, Trond Myklebust Subject: Re: [PATCH] dcache: make d_splice_alias use d_materialise_unique Message-ID: <20140206170348.GD14575@fieldses.org> References: <20140115151749.GF23999@fieldses.org> <20140117121723.GA18375@infradead.org> <20140117153917.GA26636@fieldses.org> <20140117210343.GD26636@fieldses.org> <20140117212655.GE26636@fieldses.org> <20140123212700.GA30466@fieldses.org> <20140131184258.GN10323@ZenIV.linux.org.uk> <20140131194758.GA24618@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140131194758.GA24618@fieldses.org> 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 On Fri, Jan 31, 2014 at 02:47:58PM -0500, J. Bruce Fields wrote: > (Then one remaining thing I don't understand is how to make that fixing > up reliable. Or is there some reason nobody hits the _EBUSY case of > __d_unalias?) In fact, a reproducer found thanks to Hideshi Yamaoka: On server: while true; do mv /exports/DIR /exports/TO/DIR mv /exports/TO/DIR /exports/DIR done On client: mount -olookupcache=pos /mnt while true; do ls /mnt/TO; done Also on client: while true; do strace -e open cat /mnt/DIR/test.txt 2>&1 | grep EBUSY done Once all three of those loops are running I hit open("/mnt/DIR/test.txt", O_RDONLY) = -1 EBUSY very quickly. The "lookupcache=pos" isn't really necessary but makes the reproducer more reliable. (Originally this was seen on a single client: the client itself was doing the renames but also continually killing the second mv. I suspect that means the client sends the RENAME but then fails to update its dcache, the result being again that the client's dcache is out of sync with the server's tree and hence lookup is stuck trying to grab a dentry from another directory.) Is there some solution short of making ->lookup callers drop the i_mutex and retry??? --b. -- 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/