From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: [PATCH] libata: get rid of ATA_MAX_QUEUE loop in ata_qc_complete_multiple() Date: Wed, 20 May 2009 09:40:07 +0200 Message-ID: <20090520074006.GI11363@kernel.dk> References: <20090520065752.GC11363@kernel.dk> <4A13B08D.3060005@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from brick.kernel.dk ([93.163.65.50]:52551 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754072AbZETHkG (ORCPT ); Wed, 20 May 2009 03:40:06 -0400 Content-Disposition: inline In-Reply-To: <4A13B08D.3060005@gmail.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Tejun Heo Cc: linux-ide@vger.kernel.org, jeff@garzik.org On Wed, May 20 2009, Tejun Heo wrote: > Hello, Jens. > > Jens Axboe wrote: > > @@ -5039,16 +5039,19 @@ int ata_qc_complete_multiple(struct ata_port *ap, u32 qc_active) > > return -EINVAL; > > } > > > > - for (i = 0; i < ATA_MAX_QUEUE; i++) { > > + while (done_mask) { > > struct ata_queued_cmd *qc; > > + unsigned int next = __ffs(done_mask); > > > > - if (!(done_mask & (1 << i))) > > - continue; > > - > > - if ((qc = ata_qc_from_tag(ap, i))) { > > + qc = ata_qc_from_tag(ap, i + next); > > + if (qc) { > > ata_qc_complete(qc); > > nr_done++; > > } > > + if (++next >= ATA_MAX_QUEUE) > > + break; > > Given that __ffs doesn't care how far the first bit is on most archs > (even the generic one), I think it would be simpler and more efficient > to simply do done_mask &= ~(1 << i) and loop without adding to index > and shifting. It would be easier to read as well, agree. I'll repost it in 2 secs. -- Jens Axboe