Re: [Bugme-new] [Bug 7667] New: BUG at drivers/scsi/scsi_lib.c:1118 caused by "pktsetup dvd /dev/sr0"

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Le 12.12.2006 15:21, Boaz Harrosh a écrit :
Christoph Hellwig wrote:
On Tue, Dec 12, 2006 at 11:38:42AM +0100, Christoph Hellwig wrote:
This is because the packet driver tries to send down read/write
BLOCK_PC commands that don't use a bio and do not use sg lists.
As part of the patch you mentioned I added strict assertations for that
case because the scsi layer doesn't handle those anymore.

The right fix is to replace all the packet_command stuff in the packet
driver by scsi_execute() which needs to be lifted from scsi code to
the block code for that.  I'll prepare a patch this weekend unless
someone beets me in doing that work.
Please try the patch below to fix the bug for now.  It's not the
full way to a generic execute block pc infrastcuture but should fix
the bug for the time beeing:


Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Index: linux-2.6/drivers/block/pktcdvd.c
===================================================================
--- linux-2.6.orig/drivers/block/pktcdvd.c	2006-12-12 11:30:45.000000000 +0100
+++ linux-2.6/drivers/block/pktcdvd.c	2006-12-12 14:23:37.000000000 +0100
@@ -765,47 +765,34 @@
  */
 static int pkt_generic_packet(struct pktcdvd_device *pd, struct packet_command *cgc)
 {
-	char sense[SCSI_SENSE_BUFFERSIZE];
-	request_queue_t *q;
+	request_queue_t *q = bdev_get_queue(pd->bdev);
 	struct request *rq;
-	DECLARE_COMPLETION_ONSTACK(wait);
-	int err = 0;
+	int ret = 0;
- q = bdev_get_queue(pd->bdev);
+	rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ?
+			     WRITE : READ, __GFP_WAIT);
+
+	if (cgc->buflen) {
+		if (blk_rq_map_kern(q, rq, cgc->buffer, cgc->buflen, __GFP_WAIT))
+			goto out;
+	}
+
+	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);
+	memcpy(rq->cmd, cgc->cmd, CDROM_PACKET_SIZE);
+	if (sizeof(rq->cmd) > CDROM_PACKET_SIZE)
+		memset(rq->cmd + CDROM_PACKET_SIZE, 0, sizeof(rq->cmd) - CDROM_PACKET_SIZE);
- rq = blk_get_request(q, (cgc->data_direction == CGC_DATA_WRITE) ? WRITE : READ,
-			     __GFP_WAIT);
-	rq->errors = 0;
-	rq->rq_disk = pd->bdev->bd_disk;
-	rq->bio = NULL;
-	rq->buffer = NULL;
 	rq->timeout = 60*HZ;
-	rq->data = cgc->buffer;
-	rq->data_len = cgc->buflen;
-	rq->sense = sense;
-	memset(sense, 0, sizeof(sense));
-	rq->sense_len = 0;
 	rq->cmd_type = REQ_TYPE_BLOCK_PC;
 	rq->cmd_flags |= REQ_HARDBARRIER;
 	if (cgc->quiet)
 		rq->cmd_flags |= REQ_QUIET;
-	memcpy(rq->cmd, cgc->cmd, CDROM_PACKET_SIZE);
-	if (sizeof(rq->cmd) > CDROM_PACKET_SIZE)
-		memset(rq->cmd + CDROM_PACKET_SIZE, 0, sizeof(rq->cmd) - CDROM_PACKET_SIZE);
-	rq->cmd_len = COMMAND_SIZE(rq->cmd[0]);
-
-	rq->ref_count++;
-	rq->end_io_data = &wait;
-	rq->end_io = blk_end_sync_rq;
-	elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
-	generic_unplug_device(q);
-	wait_for_completion(&wait);
-
-	if (rq->errors)
-		err = -EIO;
+ blk_execute_rq(rq->q, pd->bdev->bd_disk, rq, 0);
+	ret = rq->errors;
+out:
 	blk_put_request(rq);
-	return err;
+	return ret;
 }
/*
-
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I'm afraid this might not be enough because of code in drivers/ide/ide-cd.c. It does IO off of request->data.

[background]
pkt_generic_packet and ton of other places mainly cd(s), floppy(s), and other ide code paths,
are using what I call BLACK requests. They put some data on request->buffer or request->data
stick it in the Q and than advance on them later down the ladder. Remove of "buffer" and "data" from
struct request will reveal all these places. At one time I had plans to do just that. But 1/2 way through I gave
up, it is too risky, too much Hardware that I don't have, that needs checking.

below patch combined with your patch might get a bit closer for this code path.
At struct request I have changed the name of "data" member to "user_data". than changed the code paths that used
"data" as IO to use request->buffer instead. This is just as bad but is a more common practice.

I suspect there is a problem with what I did in scsi_lib.c Christoph please check me out with the new BUG_ON.
Mainly what you need from below is only the code in ide-cd.c.
(And there are 3-4 places that do exactly like pkt_generic_packet, though I'm not sure they end up through SCSI.
At first I thought this code doesn't either)

[patch snipped]

Christoph's patch fixed the BUG, while Boaz's patch didn't fix anything (both tested with kernel 2.6.16-rc6-mm2).
Please note I don't use ide-cd, I use libata+pata_via+sr_mod.

Boaz, when you wrote "below patch combined with your patch...", did you mean your patch should be applied on top of Christoph's one ? In this case, it fails with:
  patching file drivers/block/pktcdvd.c
  Hunk #1 FAILED at 778.
  1 out of 1 hunk FAILED -- rejects in file drivers/block/pktcdvd.c

--
laurent
-
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