Re: SCSI eats error from flush failure during hot plug

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2014-07-03 at 10:18 -0700, Christoph Hellwig wrote:
> On Thu, Jul 03, 2014 at 09:57:32AM -0700, Steven Haber wrote:
> > Both patches work fine -- zero uncommitted writes over several hundred
> > power cycles.
> 
> Thanks for the testing.
> 
> Below is James' patch with a trivial comment fix and a proper changelog.
> James, can I get your signoff for this one?  I'll throw it into the
> core-for-3.16 tree then.

OK, here it is.  I tweaked the comment to be accurate.

James

---

>From 66aba46049037b55c5c77b45974a639f8f48b58b Mon Sep 17 00:00:00 2001
From: James Bottomley <JBottomley@Parallels.com>
Date: Thu, 3 Jul 2014 19:17:34 +0200
Subject: [PATCH] [SCSI] handle flush errors properly

Flush commands don't transfer data and thus need to be special cased
in the I/O completion handler so that we can propagate errors to
the block layer and filesystem.

Reported-by: Steven Haber <steven@qumulo.com>
Tested-by: Steven Haber <steven@qumulo.com>
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f7e3163..3f50dfc 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -733,6 +733,14 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 			scsi_next_command(cmd);
 			return;
 		}
+	} else if (blk_rq_bytes(req) == 0 && result && !sense_deferred) {
+		/*
+		 * Certain non BLOCK_PC requests are commands that don't
+		 * actually transfer anything (FLUSH), so cannot use
+		 * good_bytes != blk_rq_bytes(req) as the signal for an error.
+		 * This sets the error explicitly for the problem case.
+		 */
+		error = __scsi_error_from_host_byte(cmd, result);
 	}
 
 	/* no bidi support for !REQ_TYPE_BLOCK_PC yet */