ACK/cmnt: [SRU][Xenial][Yakkety][Zesty][Artful][PATCH 1/1] blk-mq: NVMe 512B/4K+T10 DIF/DIX format returns I/O error on dd with split op

[Stefan Bader]

On 14.07.2017 17:46, Joseph Salisbury wrote:
> From: Wen Xiong <wenxiong at linux.vnet.ibm.com>
> 
> BugLink: http://bugs.launchpad.net/bugs/1689946
> 
> 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
> 
> Signed-off-by: Wen Xiong <wenxiong at linux.vnet.ibm.com>
> Signed-off-by: Jens Axboe <axboe at fb.com>
> (cherry picked from commit f36ea50ca0043e7b1204feaf1d2ba6bd68c08d36)
> Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>

> ---

SRU justification needs to be added to bug report.
>  block/blk-mq.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 567a3ed..d45989b 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1295,13 +1295,13 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
>  
>  	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;
> 


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