scsi_lib: correctly retry failed zero length REQ_TYPE_FS commands

[ Upstream commit a621bac3044ed6f7ec5fa0326491b2d4838bfa93 ]

When SCSI was written, all commands coming from the filesystem
(REQ_TYPE_FS commands) had data.  This meant that our signal for needing
to complete the command was the number of bytes completed being equal to
the number of bytes in the request.  Unfortunately, with the advent of
flush barriers, we can now get zero length REQ_TYPE_FS commands, which
confuse this logic because they satisfy the condition every time.  This
means they never get retried even for retryable conditions, like UNIT
ATTENTION because we complete them early assuming they're done.  Fix
this by special casing the early completion condition to recognise zero
length commands with errors and let them drop through to the retry code.

Cc: stable@vger.kernel.org
Reported-by: Sebastian Parschauer <s.parschauer@gmx.de>
Signed-off-by: James E.J. Bottomley <jejb@linux.vnet.ibm.com>
Tested-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index b1ab509d0e05f3ddd410ab9257b29e03d123eeee..a11837054d6c880a4e6369158ca13ae8a5f31286 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -919,9 +919,12 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
        }
 
        /*
-        * If we finished all bytes in the request we are done now.
+        * special case: failed zero length commands always need to
+        * drop down into the retry code. Otherwise, if we finished
+        * all bytes in the request we are done now.
         */
-       if (!scsi_end_request(req, error, good_bytes, 0))
+       if (!(blk_rq_bytes(req) == 0 && error) &&
+           !scsi_end_request(req, error, good_bytes, 0))
                return;
 
        /*