linux-kernel - Re: [PATCH v9 07/13] block: Add PCI P2P flag for request queue and check support for requests

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Date:   Wed, 10 Oct 2018 14:59:01 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Logan Gunthorpe <logang@...tatee.com>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-nvme@...ts.infradead.org, linux-rdma@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-block@...r.kernel.org,
        Sagi Grimberg <sagi@...mberg.me>,
        Christian König <christian.koenig@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Stephen Bates <sbates@...thlin.com>,
        Keith Busch <keith.busch@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v9 07/13] block: Add PCI P2P flag for request queue and
 check support for requests

On Fri, Oct 05, 2018 at 07:16:04PM -0600, Jens Axboe wrote:
> On 10/4/18 3:27 PM, Logan Gunthorpe wrote:
> > QUEUE_FLAG_PCI_P2P is introduced meaning a driver's request queue
> > supports targeting P2P memory. This will be used by P2P providers and
> > orchestrators (in subsequent patches) to ensure block devices can
> > support P2P memory before submitting P2P backed pages to submit_bio().
> 
> Nit pick, but the subject line still says that it checks support
> for requests. This patch just adds the ability to flag support
> in the queue.

What about the following?  MAINTAINERS doesn't list a specific
maintainer for include/linux/blkdev.h (maybe the "BLOCK LAYER" entry
should have an F: pattern for it?), but I'd really like your ack
before merging this.

commit 7e647ae1eda290786851c3dff4f38189b982386d
Author: Logan Gunthorpe <logang@...tatee.com>
Date:   Thu Oct 4 15:27:41 2018 -0600

    block: Add PCI P2P flag for request queue
    
    Add QUEUE_FLAG_PCI_P2P, meaning a driver's request queue supports targeting
    P2P memory.  This will be used by P2P providers and orchestrators (in
    subsequent patches) to ensure block devices can support P2P memory before
    submitting P2P-backed pages to submit_bio().
    
    Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
    Reviewed-by: Christoph Hellwig <hch@....de>

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 6980014357d4..c32f7171899b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -699,6 +699,7 @@ struct request_queue {
 #define QUEUE_FLAG_SCSI_PASSTHROUGH 27	/* queue supports SCSI commands */
 #define QUEUE_FLAG_QUIESCED    28	/* queue has been quiesced */
 #define QUEUE_FLAG_PREEMPT_ONLY	29	/* only process REQ_PREEMPT requests */
+#define QUEUE_FLAG_PCI_P2PDMA  30	/* device supports PCI p2p requests */
 
 #define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\
 				 (1 << QUEUE_FLAG_SAME_COMP)	|	\
@@ -731,6 +732,8 @@ bool blk_queue_flag_test_and_clear(unsigned int flag, struct request_queue *q);
 #define blk_queue_dax(q)	test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags)
 #define blk_queue_scsi_passthrough(q)	\
 	test_bit(QUEUE_FLAG_SCSI_PASSTHROUGH, &(q)->queue_flags)
+#define blk_queue_pci_p2pdma(q)	\
+	test_bit(QUEUE_FLAG_PCI_P2PDMA, &(q)->queue_flags)
 
 #define blk_noretry_request(rq) \
 	((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \