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Mon, 14 Sep 2020 14:52:16 +0000 (UTC) Received: from localhost (unknown [10.18.25.174]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 8D7CC5F9D1; Mon, 14 Sep 2020 14:52:10 +0000 (UTC) Date: Mon, 14 Sep 2020 10:52:09 -0400 From: Mike Snitzer To: Damien Le Moal Cc: Ming Lei , Vijayendra Suman , "dm-devel@redhat.com" , "linux-block@vger.kernel.org" Subject: Re: [PATCH 1/3] block: fix blk_rq_get_max_sectors() to flow more carefully Message-ID: <20200914145209.GB14410@redhat.com> References: <20200911215338.44805-1-snitzer@redhat.com> <20200911215338.44805-2-snitzer@redhat.com> <20200912135252.GA210077@T590> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sun, Sep 13 2020 at 8:43pm -0400, Damien Le Moal wrote: > On 2020/09/12 22:53, Ming Lei wrote: > > On Fri, Sep 11, 2020 at 05:53:36PM -0400, Mike Snitzer wrote: > >> blk_queue_get_max_sectors() has been trained for REQ_OP_WRITE_SAME and > >> REQ_OP_WRITE_ZEROES yet blk_rq_get_max_sectors() didn't call it for > >> those operations. > > > > Actually WRITE_SAME & WRITE_ZEROS are handled by the following if > > chunk_sectors is set: > > > > return min(blk_max_size_offset(q, offset), > > blk_queue_get_max_sectors(q, req_op(rq))); > > > >> Also, there is no need to avoid blk_max_size_offset() if > >> 'chunk_sectors' isn't set because it falls back to 'max_sectors'. > >> > >> Signed-off-by: Mike Snitzer > >> --- > >> include/linux/blkdev.h | 19 +++++++++++++------ > >> 1 file changed, 13 insertions(+), 6 deletions(-) > >> > >> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > >> index bb5636cc17b9..453a3d735d66 100644 > >> --- a/include/linux/blkdev.h > >> +++ b/include/linux/blkdev.h > >> @@ -1070,17 +1070,24 @@ static inline unsigned int blk_rq_get_max_sectors(struct request *rq, > >> sector_t offset) > >> { > >> struct request_queue *q = rq->q; > >> + int op; > >> + unsigned int max_sectors; > >> > >> if (blk_rq_is_passthrough(rq)) > >> return q->limits.max_hw_sectors; > >> > >> - if (!q->limits.chunk_sectors || > >> - req_op(rq) == REQ_OP_DISCARD || > >> - req_op(rq) == REQ_OP_SECURE_ERASE) > >> - return blk_queue_get_max_sectors(q, req_op(rq)); > >> + op = req_op(rq); > >> + max_sectors = blk_queue_get_max_sectors(q, op); > >> > >> - return min(blk_max_size_offset(q, offset), > >> - blk_queue_get_max_sectors(q, req_op(rq))); > >> + switch (op) { > >> + case REQ_OP_DISCARD: > >> + case REQ_OP_SECURE_ERASE: > >> + case REQ_OP_WRITE_SAME: > >> + case REQ_OP_WRITE_ZEROES: > >> + return max_sectors; > >> + }>> + > >> + return min(blk_max_size_offset(q, offset), max_sectors); > >> } > > > > It depends if offset & chunk_sectors limit for WRITE_SAME & WRITE_ZEROS > > needs to be considered. > > That limit is needed for zoned block devices to ensure that *any* write request, > no matter the command, do not cross zone boundaries. Otherwise, the write would > be immediately failed by the device. Thanks for the additional context, sorry to make you so concerned! ;) Mike