Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752540AbaAQMRb (ORCPT ); Fri, 17 Jan 2014 07:17:31 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:58177 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752484AbaAQMR2 (ORCPT ); Fri, 17 Jan 2014 07:17:28 -0500 Date: Fri, 17 Jan 2014 04:17:23 -0800 From: Christoph Hellwig To: "J. Bruce Fields" Cc: Al Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, Miklos Szeredi Subject: Re: [PATCH] dcache: fix d_splice_alias handling of aliases Message-ID: <20140117121723.GA18375@infradead.org> References: <20140115151749.GF23999@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140115151749.GF23999@fieldses.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 15, 2014 at 10:17:49AM -0500, J. Bruce Fields wrote: > From: "J. Bruce Fields" > > d_splice_alias can create duplicate directory aliases (in the !new > case), or (in the new case) d_move without holding appropriate locks. > > d_materialise_unique deals with both of these problems. (The latter > seems to be dealt by trylocks (see __d_unalias), which look like they > could cause spurious lookup failures--but that's at least better than > corrupting the dcache.) I'm a bit worried about those spurious failures, maybe we should retry in that case? Also looking over the changes I wonder if the explicit cecking for aliases for every non-directory might have a major performance impact, all the dcache growling already was a major issues in NFS workloads years ago and I dumb it's become any better. Also looking at this area I'd like to suggest that if you end up merging the two I'd continue using the d_splice_alias name and calling conventions. Also the inode == NULL case really should be split out from d_materialise_unique into a separate helper. It shares almost no code, is entirely undocumented to the point that I don't really understand what the purpose is, and the only caller that can get there (fuse) already branches around that case in the caller anyway. -- 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/