Patch "blk-mq: NVMe 512B/4K+T10 DIF/DIX format returns I/O error on dd with split op" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

blk-mq: NVMe 512B/4K+T10 DIF/DIX format returns I/O error on dd with split op

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:

     blk-mq-nvme-512b-4k-t10-dif-dix-format-returns-i-o-error-on-dd-with-split-op.patch

and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Wen Xiong <[email protected]>
Date: Wed, 10 May 2017 08:54:11 -0500
Subject: blk-mq: NVMe 512B/4K+T10 DIF/DIX format returns I/O error on dd with split op

From: Wen Xiong <[email protected]>

[ Upstream commit f36ea50ca0043e7b1204feaf1d2ba6bd68c08d36 ]

When formatting NVMe to 512B/4K + T10 DIf/DIX, dd with split op returns "Input/output error". Looks block layer split the bio after calling bio_integrity_prep(bio). This patch fixes the issue.

Below is how we debug this issue:
(1)format nvme to 4K block # size with type 2 DIF (2)dd with block size bigger than 1024k. oflag=direct
dd: error writing '/dev/nvme0n1': Input/output error

We added some debug code in nvme device driver. It showed us the first op and the second op have the same bi and pi address. This is not correct.

1st op: nvme0n1 Op:Wr slba 0x505 length 0x100, PI ctrl=0x1400,

	dsmgmt=0x0, AT=0x0 & RT=0x505
	Guard 0x00b1, AT 0x0000, RT physical 0x00000505 RT virtual 0x00002828

2nd op: nvme0n1 Op:Wr slba 0x605 length 0x1, PI ctrl=0x1400, dsmgmt=0x0,

	AT=0x0 & RT=0x605  ==> This op fails and subsequent 5 retires..
	Guard 0x00b1, AT 0x0000, RT physical 0x00000605 RT virtual 0x00002828

With the fix, It showed us both of the first op and the second op have correct bi and pi address.

1st op: nvme2n1 Op:Wr slba 0x505 length 0x100, PI ctrl=0x1400,

	dsmgmt=0x0, AT=0x0 & RT=0x505
	Guard 0x5ccb, AT 0x0000, RT physical 0x00000505 RT virtual
	0x00002828
2nd op: nvme2n1 Op:Wr slba 0x605 length 0x1, PI ctrl=0x1400, dsmgmt=0x0,
	AT=0x0 & RT=0x605
	Guard 0xab4c, AT 0x0000, RT physical 0x00000605 RT virtual
	0x00003028

---
 block/blk-mq.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -1252,13 +1252,13 @@ static blk_qc_t blk_mq_make_request(stru
 
 	blk_queue_bounce(q, &bio);
 
+	blk_queue_split(q, &bio, q->bio_split);
+
 	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
 		bio_io_error(bio);
 		return BLK_QC_T_NONE;
 	}
 
-	blk_queue_split(q, &bio, q->bio_split);
-
 	if (!is_flush_fua && !blk_queue_nomerges(q) &&
 	    blk_attempt_plug_merge(q, bio, &request_count, &same_queue_rq))
 		return BLK_QC_T_NONE;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/blk-mq-nvme-512b-4k-t10-dif-dix-format-returns-i-o-error-on-dd-with-split-op.patch