[SCSI] fix recovered error handling

We have a problem with recovered error handling in that any command
which goes down as BLOCK_PC but which returns a sense code of RECOVERED
ERROR gets completed with -EIO.  For actual SG_IO commands, this doesn't
matter at all, since the error return code gets dropped in favour of
req->errors which contain the SCSI completion code.

However, if this command is part of the block system, then it will pay
attention to the returned error code.  In particularly if a SYNCHRONIZE
CACHE from a barrier command completes with RECOVERED ERROR, the
resulting -EIO on the barrier causes block to error the request and
return it to the filesystem.  Fix this by converting the -EIO for
recovered error to zero, plus remove the printing of this from sd and sr
so the message isn't double printed.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 4b13e36d3aa0..d1cb64ad1a3f 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -791,7 +791,22 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
                                       "%d bytes done.\n",
                                       req->nr_sectors, good_bytes));
 
-        /* A number of bytes were successfully read.  If there
+        /*
+         * Recovered errors need reporting, but they're always treated
+         * as success, so fiddle the result code here.  For BLOCK_PC
+         * we already took a copy of the original into rq->errors which
+         * is what gets returned to the user
+         */
+        if (sense_valid && sshdr.sense_key == RECOVERED_ERROR) {
+                if (!(req->cmd_flags & REQ_QUIET))
+                        scsi_print_sense("", cmd);
+                result = 0;
+                /* BLOCK_PC may have set error */
+                error = 0;
+        }
+
+        /*
+         * A number of bytes were successfully read.  If there
          * are leftovers and there is some kind of error
          * (result != 0), retry the rest.
          */