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Commit 1ad7c311 authored by Tony Breeds's avatar Tony Breeds Committed by Linus Torvalds
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[PATCH] Fix soft lockup with iSeries viocd driver 



Fix soft lockup with iSeries viocd driver, caused by eventually calling
end_that_request_first() with nr_bytes 0.

Some versions of hald do an SG_IO ioctl on the viocd device which becomes a
request with hard_nr_sectors and hard_cur_sectors set to zero.  Passing zero
as the number of sectors to end_request() (which calls
end_that_request_first()) causes an infinite loop when the bio is being freed.

This patch makes sure that the zero is never passed.  It only requires some
number larger the the request size the terminate the loop.

The lockup is triggered by hald, interrogating the device.

Signed-off-by: default avatarTony Breeds <tony@bakeyournoodle.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 5fdc2abe

drivers/cdrom/viocd.c

+23 −4
Original line number Diff line number Diff line
@@ -376,6 +376,25 @@ static int send_request(struct request *req) 
	return 0;

}



static void viocd_end_request(struct request *req, int uptodate)

{

	int nsectors = req->hard_nr_sectors;



	/*

	 * Make sure it's fully ended, and ensure that we process

	 * at least one sector.

	 */

	if (blk_pc_request(req))

		nsectors = (req->data_len + 511) >> 9;

	if (!nsectors)

		nsectors = 1;



	if (end_that_request_first(req, uptodate, nsectors))

		BUG();

	add_disk_randomness(req->rq_disk);

	blkdev_dequeue_request(req);

	end_that_request_last(req, uptodate);

}



static int rwreq;
@@ -385,11 +404,11 @@ static void do_viocd_request(request_queue_t *q) 


	while ((rwreq == 0) && ((req = elv_next_request(q)) != NULL)) {

		if (!blk_fs_request(req))

			end_request(req, 0);

			viocd_end_request(req, 0);

		else if (send_request(req) < 0) {

			printk(VIOCD_KERN_WARNING

					"unable to send message to OS/400!");

			end_request(req, 0);

			viocd_end_request(req, 0);

		} else

			rwreq++;

	}
@@ -601,9 +620,9 @@ static void vio_handle_cd_event(struct HvLpEvent *event) 
					"with rc %d:0x%04X: %s\n",

					req, event->xRc,

					bevent->sub_result, err->msg);

			end_request(req, 0);

			viocd_end_request(req, 0);

		} else

			end_request(req, 1);

			viocd_end_request(req, 1);



		/* restart handling of incoming requests */

		spin_unlock_irqrestore(&viocd_reqlock, flags);