From: Luben Tuikov <[EMAIL PROTECTED]>
- If the device reports an uncorrectable MEDIUM ERROR, such as SK MEDIUM
ERROR, ASC UNRECOVERED READ ERR, AMNF DATA FIELD or RECORD NOT FOUND,
then: In scsi_check_sense() return SUCCESS so as to not retry -- the
error is uncorrectable -- this speeds up total processing time.
- In scsi_io_completion(), retry if and only if there was at least one
byte completed, i.e. good_bytes != 0. If good_bytes == 0, don't try to
retry.
Without this patch, SCSI Core gets hung reading sector 0 forever, for
example when reading the partition table of a (newly discovered) device.
Here is what happens: sector 0 is broken -- the device cannot read the media
at that location. The device properly returns a certain type of uncorrectable
MEDIUM ERROR (ASC: UNRECOVERABLE READ ERR).
SCSI Core loops around its retries (which this patch fixes) and eventually
gives up and sends it for "completion". This is what happens when
scsi_check_sense() returns NEEDS_RETRY to scsi_decide_disposition() to
scsi_softirq(). The first chunk of the patch fixes this.
We end up in scsi_io_completion(), where good_bytes = 0, and result =
0x08000002 (DRIVER SENSE and CHECK CONDITION).
This statement in scsi_io_completion() causes the infinite retry loop:
if (scsi_end_request(cmd, 1, good_bytes, !!result) == NULL)
return;
substitute to get: scsi_end_request(cmd, uptodate=1, uptodate bytes=0,
retry=1) Yeah, but it doesn't make sense to call scsi_end_request() with
uptodate=1 and uptodate bytes = 0. This causes the infinite retry, since the
code tries to re-read the whole xfer size (0 bytes were uptodate and retry=1),
from the bad media.
That is, we want to set uptodate=1 iff there was at least 1 byte up to date.
Else if nothing was read, uptodate bytes = 0, then we should pass uptodate =
0, uptodate_bytes = total xfer, to mean the whole xfer is not uptodate; and
retry iff there was no error. (This is the very bottom of the function.)
Signed-off-by: Luben Tuikov <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
drivers/scsi/scsi_error.c | 5 +++++
drivers/scsi/scsi_lib.c | 3 ++-
2 files changed, 7 insertions(+), 1 deletion(-)
diff -puN
drivers/scsi/scsi_error.c~fix-sense-key-medium-error-processing-and-retry
drivers/scsi/scsi_error.c
--- a/drivers/scsi/scsi_error.c~fix-sense-key-medium-error-processing-and-retry
+++ a/drivers/scsi/scsi_error.c
@@ -359,6 +359,11 @@ static int scsi_check_sense(struct scsi_
return SUCCESS;
case MEDIUM_ERROR:
+ if (sshdr.asc == 0x11 || /* UNRECOVERED READ ERR */
+ sshdr.asc == 0x13 || /* AMNF DATA FIELD */
+ sshdr.asc == 0x14) { /* RECORD NOT FOUND */
+ return SUCCESS;
+ }
return NEEDS_RETRY;
case HARDWARE_ERROR:
diff -puN
drivers/scsi/scsi_lib.c~fix-sense-key-medium-error-processing-and-retry
drivers/scsi/scsi_lib.c
--- a/drivers/scsi/scsi_lib.c~fix-sense-key-medium-error-processing-and-retry
+++ a/drivers/scsi/scsi_lib.c
@@ -871,7 +871,8 @@ void scsi_io_completion(struct scsi_cmnd
* are leftovers and there is some kind of error
* (result != 0), retry the rest.
*/
- if (scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
+ if (good_bytes &&
+ scsi_end_request(cmd, 1, good_bytes, result == 0) == NULL)
return;
/* good_bytes = 0, or (inclusive) there were leftovers and
_
-
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