From a621bac3044ed6f7ec5fa0326491b2d4838bfa93 Mon Sep 17 00:00:00 2001 From: James Bottomley <James.Bottomley@HansenPartnership.com> Date: Fri, 13 May 2016 12:04:06 -0700 Subject: [PATCH] scsi_lib: correctly retry failed zero length REQ_TYPE_FS commands 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> --- drivers/scsi/scsi_lib.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index b2e332af0f51f..c71344aebdbb1 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -821,9 +821,12 @@ 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; /* -- 2.30.2