Re: SCSI eats error from flush failure during hot plug

James Bottomley
2014-06-26T18:52:37Z

On Thu, 2014-06-26 at 08:02 -0700, Christoph Hellwig wrote:
> Hi Steven,
>
> can you test the patch below?
>
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index f7e3163..9b56e48 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 (req->cmd_flags & REQ_FLUSH) {
> + /*
> + * Flush request don't transfer data, so we can't try
> + * to complete the good bytes first before checking
> + * the error.
> + */
> + if (result && !sense_deferred)
> + error = __scsi_error_from_host_byte(cmd, result);

Well, no, that's wrong. To catch all of the corner cases that slip
through here, the check is for a zero length command with and error
otherwise we get the same problem for failed discards.

This is what the check should be.

James

---

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index f7e3163..83e447e 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, DISCARD), so cannot use
+ * good_bytes == 0 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 */