Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751984AbaKCMWO (ORCPT ); Mon, 3 Nov 2014 07:22:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60051 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751175AbaKCMWN (ORCPT ); Mon, 3 Nov 2014 07:22:13 -0500 Message-ID: <54577368.9060000@redhat.com> Date: Mon, 03 Nov 2014 13:22:00 +0100 From: Laszlo Ersek User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 MIME-Version: 1.0 To: Vitaly Kuznetsov , Konrad Rzeszutek Wilk CC: Boris Ostrovsky , David Vrabel , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, Jeff Moyer , Andrew Jones Subject: Re: [PATCH] xen/blkfront: improve protection against issuing unsupported REQ_FUA References: <1414417478-20268-1-git-send-email-vkuznets@redhat.com> In-Reply-To: <1414417478-20268-1-git-send-email-vkuznets@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/27/14 14:44, Vitaly Kuznetsov wrote: > Guard against issuing unsupported REQ_FUA and REQ_FLUSH was introduced > in d11e61583 and was factored out into blkif_request_flush_valid() in > 0f1ca65ee. However: > 1) This check in incomplete. In case we negotiated to feature_flush = REQ_FLUSH > and flush_op = BLKIF_OP_FLUSH_DISKCACHE (so FUA is unsupported) FUA request > will still pass the check. > 2) blkif_request_flush_valid() is misnamed. It is bool but returns true when > the request is invalid. > 3) When blkif_request_flush_valid() fails -EIO is being returned. It seems that > -EOPNOTSUPP is more appropriate here. > Fix all of the above issues. > > This patch is based on the original patch by Laszlo Ersek and a comment by > Jeff Moyer. > > Signed-off-by: Vitaly Kuznetsov > --- > drivers/block/xen-blkfront.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c > index 5ac312f..2e6c103 100644 > --- a/drivers/block/xen-blkfront.c > +++ b/drivers/block/xen-blkfront.c > @@ -582,12 +582,14 @@ static inline void flush_requests(struct blkfront_info *info) > notify_remote_via_irq(info->irq); > } > > -static inline bool blkif_request_flush_valid(struct request *req, > - struct blkfront_info *info) > +static inline bool blkif_request_flush_invalid(struct request *req, > + struct blkfront_info *info) > { > return ((req->cmd_type != REQ_TYPE_FS) || > - ((req->cmd_flags & (REQ_FLUSH | REQ_FUA)) && > - !info->flush_op)); > + ((req->cmd_flags & REQ_FLUSH) && > + !(info->feature_flush & REQ_FLUSH)) || > + ((req->cmd_flags & REQ_FUA) && > + !(info->feature_flush & REQ_FUA))); > } > > /* > @@ -612,8 +614,8 @@ static void do_blkif_request(struct request_queue *rq) > > blk_start_request(req); > > - if (blkif_request_flush_valid(req, info)) { > - __blk_end_request_all(req, -EIO); > + if (blkif_request_flush_invalid(req, info)) { > + __blk_end_request_all(req, -EOPNOTSUPP); > continue; > } > > Not sure if there has been some feedback yet (I can't see anything threaded with this message in my inbox). FWIW I consulted "Documentation/block/writeback_cache_control.txt" for this review. Apparently, REQ_FLUSH forces out "previously completed write requests", whereas REQ_FUA delays the IO completion signal for *this* request until "the data has been committed to non-volatile storage". So, indeed, support for REQ_FLUSH only does not guarantee that REQ_FUA can be served. Reviewed-by: Laszlo Ersek Thanks Laszlo -- 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/