Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751916Ab3CSLFT (ORCPT ); Tue, 19 Mar 2013 07:05:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:8862 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750971Ab3CSLFR (ORCPT ); Tue, 19 Mar 2013 07:05:17 -0400 Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: References: <1363184193-1796-3-git-send-email-miklos@szeredi.hu> <1363184193-1796-1-git-send-email-miklos@szeredi.hu> <1944.1363525619@warthog.procyon.org.uk> <20130318153936.GB28508@quack.suse.cz> <20130318215333.GE21522@ZenIV.linux.org.uk> <20130318230103.GF21522@ZenIV.linux.org.uk> <20130319013805.GG21522@ZenIV.linux.org.uk> To: Miklos Szeredi Cc: dhowells@redhat.com, Al Viro , Jan Kara , torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, akpm@linux-foundation.org, apw@canonical.com, nbd@openwrt.org, neilb@suse.de, jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu, sedat.dilek@googlemail.com, hooanon05@yahoo.co.jp, mszeredi@suse.cz Subject: Re: [PATCH 2/9] vfs: export do_splice_direct() to modules Date: Tue, 19 Mar 2013 11:04:10 +0000 Message-ID: <28283.1363691050@warthog.procyon.org.uk> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 913 Lines: 21 Miklos Szeredi wrote: > > BTW, I wonder what's the right locking for that sucker; overlayfs is > > probably too heavy - we are talking about copying a file from one fs to > > another, which can obviously take quite a while, so holding ->i_mutex on > > _parent_ all along is asking for very serious contention. > > Copy up is a once-in-a-lifetime event for an object. Optimizing it is > way down in the list of things to do. I'd drop splice in a jiffy if > it's in the way. Yes, but it could block the parent directory for a long time. I suspect it's fine if you can RCU walk through the parent, but if you have to grab a lock on it... David -- 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/