On Fri, Oct 05, 2018 at 07:16:04PM -0600, Jens Axboe wrote:

On 10/4/18 3:27 PM, Logan Gunthorpe wrote:

quoted

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 [off-list ref]
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 [off-list ref]
    Signed-off-by: Bjorn Helgaas [off-list ref]
    Reviewed-by: Christoph Hellwig [off-list ref]

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| \