Bug 300871 - Busy status on tape write results in incorrect residual returned to tape driver
Busy status on tape write results in incorrect residual returned to tape driver
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kernel (Show other bugs)
All Linux
medium Severity medium
: ---
: ---
Assigned To: Jonathan Lim
Martin Jenner
: Reopened
Depends On:
Blocks: 425461
  Show dependency treegraph
Reported: 2007-09-21 13:45 EDT by Jonathan Lim
Modified: 2008-05-21 10:55 EDT (History)
9 users (show)

See Also:
Fixed In Version: RHBA-2008-0314
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2008-05-21 10:55:50 EDT
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
linux-2.6-scsi-clear-resid.patch (418 bytes, patch)
2007-09-26 14:55 EDT, Jonathan Lim
no flags Details | Diff

  None (edit)
Description Jonathan Lim 2007-09-21 13:45:35 EDT
Description of problem:

A scsi i/o request to a tape drive can receive a "stale" residual when an
immediate mode rewind request is in progress.   The i/o request receives a BUSY
response from the tape drive.  The low-level driver sets the residual field of
the scsi request to the request length and returns

  (DID_OK << 16) | scsi_status

in the result field.  The result field contains "8" which breaks down as
status_byte(result) == 4, i.e. BUSY.

scsi_softirq_done() calls scsi_decide_disposition() which returns
ADD_TO_MLQUEUE.  scsi_softirq_done() then calls scsi_queue_insert() which, on
the way to resubmitting the request to the driver, calls scsi_init_cmd_errh().

The following patch modifies scsi_init_cmd_errh() to zero the residual before
the command is (re)submitted.  This results in the correct residual being
returned when the command finally completes.

The patch was posted to linux-scsi mailing list on September 17, 2007, and
applies to 2.6.23-rc6-git7.  It should apply (+/-) to rhel5-latest.

--- linux-2.6.23-rc6-git7.orig/drivers/scsi/scsi_lib.c  2007-09-17
14:02:03.000000000 -0700
+++ linux-2.6.23-rc6-git7/drivers/scsi/scsi_lib.c       2007-09-17
14:05:51.000000000 -0700
@@ -443,6 +443,7 @@ EXPORT_SYMBOL_GPL(scsi_execute_async);
 static void scsi_init_cmd_errh(struct scsi_cmnd *cmd)
        cmd->serial_number = 0;
+       cmd->resid = 0;
        memset(cmd->sense_buffer, 0, sizeof cmd->sense_buffer);
        if (cmd->cmd_len == 0)
                cmd->cmd_len = COMMAND_SIZE(cmd->cmnd[0]);

Version-Release number of selected component (if applicable):

How reproducible:

During tape write when immediate mode rewind request is in progress.

Steps to Reproduce:

See description above.
Actual results:

Incorrect residual value returned.

Expected results:

Residual value 0 returned.

Additional info:

A diff to the RHEL5.1 kernel source will be posted here once the patch has been
confirmed to be upstream.
Comment 2 RHEL Product and Program Management 2007-09-26 14:54:19 EDT
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update
Comment 3 Jonathan Lim 2007-09-26 14:55:19 EDT
Created attachment 207371 [details]

Diff against 2.6.18-47.el5 kernel source.
Comment 4 Jonathan Lim 2007-09-27 14:39:46 EDT
Changed status per instructions from Don Zickus.
Comment 6 Don Zickus 2007-11-29 12:07:00 EST
in 2.6.18-58.el5
You can download this test kernel from http://people.redhat.com/dzickus/el5
Comment 7 Jonathan Lim 2008-01-04 16:37:02 EST
Fix verified at SGI.
Comment 11 errata-xmlrpc 2008-05-21 10:55:50 EDT
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.


Note You need to log in before you can comment on or make changes to this bug.