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Date: Thu, 19 Feb 2009 15:58:44 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Sitsofe Wheeler <sitsofe@...oo.com>
Cc: linux-kernel@...r.kernel.org,
Alan Stern <stern@...land.harvard.edu>,
James Bottomley <James.Bottomley@...senPartnership.com>
Subject: Re: [SCSI][REGRESSION][BISECTED] Disk errors loop forever in 2.6.29
* Sitsofe Wheeler <sitsofe@...oo.com> wrote:
> Hi,
>
> There appears to be a regression from 2.6.28 in how disk errors are
> handled in 2.6.29rc5 - rather than trying and eventually giving up, it
> appears to try (and report) forever.
>
> Here is the output where it aborts in 2.6.28:
>
> ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
> ata2.01: BMDMA stat 0x65
> ata2.01: cmd c8/00:00:f7:e2:9c/00:00:00:00:00/f1 tag 0 dma 131072 in
> res 00/00:00:00:00:00/00:00:00:00:00/00 Emask 0x2 (HSM violation)
> ata2: soft resetting link
> ata2.00: configured for UDMA/66
> ata2.01: configured for UDMA/66
> ata2: EH complete
> ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
> ata2.01: BMDMA stat 0x65
> ata2.01: cmd c8/00:00:f7:e2:9c/00:00:00:00:00/f1 tag 0 dma 131072 in
> res 00/00:00:00:00:00/00:00:00:00:00/00 Emask 0x2 (HSM violation)
> ata2: soft resetting link
> ata2.00: configured for UDMA/66
> ata2.01: configured for UDMA/66
> ata2: EH complete
> sd 1:0:0:0: [sda] 7880544 512-byte hardware sectors: (4.03 GB/3.75 GiB)
> ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
> ata2.01: BMDMA stat 0x65
> ata2.01: cmd c8/00:00:f7:e2:9c/00:00:00:00:00/f1 tag 0 dma 131072 in
> res 00/00:00:00:00:00/00:00:00:00:00/00 Emask 0x2 (HSM violation)
> ata2: soft resetting link
> ata2.00: configured for UDMA/66
> ata2.01: configured for UDMA/66
> ata2: EH complete
> sd 1:0:0:0: [sda] Write Protect is off
> sd 1:0:0:0: [sda] Mode Sense: 00 3a 00 00
> ata2.01: limiting speed to UDMA/44:PIO4
> ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
> ata2.01: BMDMA stat 0x65
> ata2.01: cmd c8/00:00:f7:e2:9c/00:00:00:00:00/f1 tag 0 dma 131072 in
> res 00/00:00:00:00:00/00:00:00:00:00/00 Emask 0x2 (HSM violation)
> ata2: soft resetting link
> ata2.00: configured for UDMA/66
> ata2.01: configured for UDMA/44
> ata2: EH complete
> ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
> ata2.01: BMDMA stat 0x65
> ata2.01: cmd c8/00:00:f7:e2:9c/00:00:00:00:00/f1 tag 0 dma 131072 in
> res 00/00:00:00:00:00/00:00:00:00:00/00 Emask 0x2 (HSM violation)
> ata2: soft resetting link
> ata2.00: configured for UDMA/66
> ata2.01: configured for UDMA/44
> ata2: EH complete
> sd 1:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
> sda: detected capacity change from 0 to 4034838528
> ata2.01: limiting speed to UDMA/33:PIO4
> ata2.01: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6
> ata2.01: BMDMA stat 0x65
> ata2.01: cmd c8/00:00:f7:e2:9c/00:00:00:00:00/f1 tag 0 dma 131072 in
> res 00/00:00:00:00:00/00:00:00:00:00/00 Emask 0x2 (HSM violation)
> ata2: soft resetting link
> ata2.00: configured for UDMA/66
> ata2.01: configured for UDMA/33
> sd 1:0:1:0: [sdb] Result: hostbyte=0x00 driverbyte=0x08
> sd 1:0:1:0: [sdb] Sense Key : 0xb [current] [descriptor]
> Descriptor sense data with sense descriptors (in hex):
> 72 0b 00 00 00 00 00 0c 00 0a 80 00 00 00 00 00
> 00 00 00 00
> sd 1:0:1:0: [sdb] ASC=0x0 ASCQ=0x0
> end_request: I/O error, dev sdb, sector 27058935
> Buffer I/O error on device sdb2, logical block 444480
> Buffer I/O error on device sdb2, logical block 444481
> Buffer I/O error on device sdb2, logical block 444482
> Buffer I/O error on device sdb2, logical block 444483
> Buffer I/O error on device sdb2, logical block 444484
> Buffer I/O error on device sdb2, logical block 444485
> Buffer I/O error on device sdb2, logical block 444486
> Buffer I/O error on device sdb2, logical block 444487
> Buffer I/O error on device sdb2, logical block 444488
> Buffer I/O error on device sdb2, logical block 444489
> ata2: EH complete
>
> It never gets to end_request on 2.6.29. I've bisected the problem down
> to the following:
>
> [b60af5b0adf0da24c673598c8d3fb4d4189a15ce] [SCSI] simplify scsi_io_completion()
>
> Author: Alan Stern <stern@...land.harvard.edu>
> Date: Mon Nov 3 15:56:47 2008 -0500
>
> [SCSI] simplify scsi_io_completion()
i had SCSI problems with that area of the code, and the patch
below fixed it. Maybe it fixes your problem too.
Ingo
----------------------->
>From 7e4cbd14b28546e6f758d01b0d7f3f4647fada52 Mon Sep 17 00:00:00 2001
From: Alan Stern <stern@...land.harvard.edu>
Date: Tue, 17 Feb 2009 15:10:21 -0500
Subject: [PATCH] fix "scsi: aic7xxx hang since v2.6.28-rc1"
This patch (as1144c) removes scsi_end_request(). The routine had only
one caller, so it is moved inline and simplified.
In addition, if no forward progress has been made then the patch
decrements a request's retry counter before unpreparing and requeuing
it, to avoid infinite retry loops.
Signed-off-by: Alan Stern <stern@...land.harvard.edu>
Cc: James Bottomley <James.Bottomley@...senPartnership.com>
Cc: Jens Axboe <jens.axboe@...cle.com>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
drivers/scsi/scsi_lib.c | 94 ++++++++++-------------------------------------
1 files changed, 20 insertions(+), 74 deletions(-)
diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 940dc32..d4c6ac3 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -703,71 +703,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
static void __scsi_release_buffers(struct scsi_cmnd *, int);
-/*
- * Function: scsi_end_request()
- *
- * Purpose: Post-processing of completed commands (usually invoked at end
- * of upper level post-processing and scsi_io_completion).
- *
- * Arguments: cmd - command that is complete.
- * error - 0 if I/O indicates success, < 0 for I/O error.
- * bytes - number of bytes of completed I/O
- * requeue - indicates whether we should requeue leftovers.
- *
- * Lock status: Assumed that lock is not held upon entry.
- *
- * Returns: cmd if requeue required, NULL otherwise.
- *
- * Notes: This is called for block device requests in order to
- * mark some number of sectors as complete.
- *
- * We are guaranteeing that the request queue will be goosed
- * at some point during this call.
- * Notes: If cmd was requeued, upon return it will be a stale pointer.
- */
-static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
- int bytes, int requeue)
-{
- struct request_queue *q = cmd->device->request_queue;
- struct request *req = cmd->request;
-
- /*
- * If there are blocks left over at the end, set up the command
- * to queue the remainder of them.
- */
- if (blk_end_request(req, error, bytes)) {
- int leftover = (req->hard_nr_sectors << 9);
-
- if (blk_pc_request(req))
- leftover = req->data_len;
-
- /* kill remainder if no retrys */
- if (error && scsi_noretry_cmd(cmd))
- blk_end_request(req, error, leftover);
- else {
- if (requeue) {
- /*
- * Bleah. Leftovers again. Stick the
- * leftovers in the front of the
- * queue, and goose the queue again.
- */
- scsi_release_buffers(cmd);
- scsi_requeue_command(q, cmd);
- cmd = NULL;
- }
- return cmd;
- }
- }
-
- /*
- * This will goose the queue request function at the end, so we don't
- * need to worry about launching another command.
- */
- __scsi_release_buffers(cmd, 0);
- scsi_next_command(cmd);
- return NULL;
-}
-
static inline unsigned int scsi_sgtable_index(unsigned short nents)
{
unsigned int index;
@@ -929,7 +864,6 @@ static void scsi_end_bidi_request(struct scsi_cmnd *cmd)
void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
{
int result = cmd->result;
- int this_count;
struct request_queue *q = cmd->device->request_queue;
struct request *req = cmd->request;
int error = 0;
@@ -980,18 +914,30 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
SCSI_LOG_HLCOMPLETE(1, printk("%ld sectors total, "
"%d bytes done.\n",
req->nr_sectors, good_bytes));
-
- /* A number of bytes were successfully read. If there
- * are leftovers and there is some kind of error
- * (result != 0), retry the rest.
- */
- if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
+ if (blk_end_request(req, error, good_bytes) == 0) {
+ /* This request is completely finished; start the next one */
+ scsi_next_command(cmd);
return;
- this_count = blk_rq_bytes(req);
+ }
error = -EIO;
- if (host_byte(result) == DID_RESET) {
+ /* The request isn't finished yet. Figure out what to do next. */
+ if (result == 0) {
+ /* No error, so carry out the remainder of the request.
+ * Failure to make forward progress counts against the
+ * the number of retries.
+ */
+ if (good_bytes > 0 || --req->retries >= 0)
+ action = ACTION_REPREP;
+ else {
+ action = ACTION_FAIL;
+ description = "Retries exhausted";
+ }
+ } else if (error && scsi_noretry_cmd(cmd)) {
+ /* Retrys are disallowed, so kill the remainder. */
+ action = ACTION_FAIL;
+ } else if (host_byte(result) == DID_RESET) {
/* Third party bus reset or reset for error recovery
* reasons. Just retry the command and see what
* happens.
--
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