[PATCH 0/2] block,scsi: BLK_STS_AGAIN clarification

[PATCH 0/2] block,scsi: BLK_STS_AGAIN clarification

[Hannes Reinecke]

Hi all,

BLK_STS_AGAIN should only be used under very specify circumstances,
so we should better document that. And modify the SCSI midlayer to
not return it, of course.

As usual, comments and reviews are welcome.

Hannes Reinecke (2):
  block: document BLK_STS_AGAIN usage
  scsi: return BLK_STS_TRANSPORT for ALUA transitioning

 drivers/scsi/scsi_lib.c   | 2 +-
 include/linux/blk_types.h | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

-- 
2.29.2

[PATCH 1/2] block: document BLK_STS_AGAIN usage

[Hannes Reinecke]

BLK_STS_AGAIN should only be used if RQF_NOWAIT is set and the bio
would block. So we'd better document that to avoid accidental misuse.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 include/linux/blk_types.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 1973ef9bd40f..8fb8f79cb74e 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -105,6 +105,10 @@ typedef u16 blk_short_t;
 /* hack for device mapper, don't use elsewhere: */
 #define BLK_STS_DM_REQUEUE    ((__force blk_status_t)11)
 
+/*
+ * BLK_STS_AGAIN should only be returned if RQF_NOWAIT is set
+ * and the bio would block (cf bio_wouldblock_error())
+ */
 #define BLK_STS_AGAIN		((__force blk_status_t)12)
 
 /*
-- 
2.29.2

Re: [PATCH 1/2] block: document BLK_STS_AGAIN usage

[Christoph Hellwig]

On Tue, May 24, 2022 at 07:56:30AM +0200, Hannes Reinecke wrote:
> BLK_STS_AGAIN should only be used if RQF_NOWAIT is set and the bio
> would block. So we'd better document that to avoid accidental misuse.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

given that nothing in patch 2 depends on this it would be good to just
get this into the block tree ASAP.

Re: [PATCH 1/2] block: document BLK_STS_AGAIN usage

[Chaitanya Kulkarni]

On 5/23/22 22:56, Hannes Reinecke wrote:
> BLK_STS_AGAIN should only be used if RQF_NOWAIT is set and the bio
> would block. So we'd better document that to avoid accidental misuse.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---


Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck

[PATCH 2/2] scsi: return BLK_STS_TRANSPORT for ALUA transitioning

[Hannes Reinecke]

When the 'ALUA state transitioning' sense code is returned we
cannot use BLK_STS_AGAIN, as this has a very specific use-case.
So return BLK_STS_TRANSPORT here.

Signed-off-by: Hannes Reinecke <hare@suse.de>
---
 drivers/scsi/scsi_lib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 8d18cc7e510e..a55deb5caa34 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -779,7 +779,7 @@ static void scsi_io_completion_action(struct scsi_cmnd *cmd, int result)
 					action = ACTION_DELAYED_RETRY;
 					break;
 				case 0x0a: /* ALUA state transition */
-					blk_stat = BLK_STS_AGAIN;
+					blk_stat = BLK_STS_TRANSPORT;
 					fallthrough;
 				default:
 					action = ACTION_FAIL;
-- 
2.29.2

Re: [PATCH 2/2] scsi: return BLK_STS_TRANSPORT for ALUA transitioning

[Chaitanya Kulkarni]

On 5/23/22 22:56, Hannes Reinecke wrote:
> When the 'ALUA state transitioning' sense code is returned we
> cannot use BLK_STS_AGAIN, as this has a very specific use-case.
> So return BLK_STS_TRANSPORT here.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---

Do we need a fixes tag ? irrespective of that looks good.

Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>

-ck

Re: [PATCH 2/2] scsi: return BLK_STS_TRANSPORT for ALUA transitioning

[Martin K. Petersen]

Hannes,

> When the 'ALUA state transitioning' sense code is returned we cannot
> use BLK_STS_AGAIN, as this has a very specific use-case.  So return
> BLK_STS_TRANSPORT here.

Applied to 5.19/scsi-staging, thanks!

-- 
Martin K. Petersen	Oracle Linux Engineering

Re: (subset) [PATCH 0/2] block,scsi: BLK_STS_AGAIN clarification

[Jens Axboe]

On Tue, 24 May 2022 07:56:29 +0200, Hannes Reinecke wrote:
> BLK_STS_AGAIN should only be used under very specify circumstances,
> so we should better document that. And modify the SCSI midlayer to
> not return it, of course.
> 
> As usual, comments and reviews are welcome.
> 
> Hannes Reinecke (2):
>   block: document BLK_STS_AGAIN usage
>   scsi: return BLK_STS_TRANSPORT for ALUA transitioning
> 
> [...]

Applied, thanks!

[1/2] block: document BLK_STS_AGAIN usage
      commit: 98d40e76652e9aeb3aec4065f600d633ed335e94

Best regards,
-- 
Jens Axboe