Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759372Ab2HHXrs (ORCPT ); Wed, 8 Aug 2012 19:47:48 -0400 Received: from mail-qa0-f53.google.com ([209.85.216.53]:64806 "EHLO mail-qa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753039Ab2HHXrr (ORCPT ); Wed, 8 Aug 2012 19:47:47 -0400 MIME-Version: 1.0 In-Reply-To: <20120808232804.GL6983@dhcp-172-17-108-109.mtv.corp.google.com> References: <1344290921-25154-1-git-send-email-koverstreet@google.com> <1344290921-25154-13-git-send-email-koverstreet@google.com> <20120808232804.GL6983@dhcp-172-17-108-109.mtv.corp.google.com> Date: Wed, 8 Aug 2012 16:47:46 -0700 Message-ID: Subject: Re: [dm-devel] [PATCH v5 12/12] block: Only clone bio vecs that are in use From: Muthu Kumar To: Tejun Heo Cc: Mikulas Patocka , device-mapper development , linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org, axboe@kernel.dk, Kent Overstreet , vgoyal@redhat.com, yehuda@hq.newdream.net, sage@newdream.net, agk@redhat.com, drbd-dev@lists.linbit.com Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1967 Lines: 56 Tejun, This is changing the semantics of the clone. Sorry, I missed this thread and replied separately. But anyway, replying it again here: On Wed, Aug 8, 2012 at 4:28 PM, Tejun Heo wrote: > On Mon, Aug 06, 2012 at 07:16:33PM -0400, Mikulas Patocka wrote: >> Hi Kent >> >> When you change the semantics of an exported function, rename that >> function. There may be external modules that use __bio_clone and this >> change could silently introduce bugs in them. >> >> Otherwise, the patchset looks fine. > > I don't know. This doesn't change the main functionality and should > be transparent unless the caller is doing something crazy. It *might* > be nice to rename but I don't think that's a must here. > > Thanks. -- You are changing the meaning of __bio_clone() here. In old code, the number of io_vecs, bi_idx, bi_vcnt are preserved. But in this modified code, you are mapping bio_src's bi_iovec[bi_idx] to bio_dests bi_iovec[0] and also restricting the number of allocated io_vecs of the clone. It may be useful for cases were we would like a identical copy of the original bio (may not be in current code base, but this implementation is definitely not what one would expect from the name "clone"). May be, call this new implementation some thing else (and use it for bcache)? --- Like Mikulas pointed out, this is an exported function and silently changing the semantics will break external modules. Regards, Muthu > > -- > tejun > -- > 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/ -- 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/