drivers/block/ll_rw_blk.c |   49 ++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/blkdev.h    |    1 
 2 files changed, 50 insertions(+)

--- linux-2.6.0-test6/drivers/block/ll_rw_blk.c~dev_read_only_2.6.0	2003-10-14 19:56:55.000000000 +0400
+++ linux-2.6.0-test6-alexey/drivers/block/ll_rw_blk.c	2003-10-22 01:35:56.000000000 +0400
@@ -2213,6 +2213,9 @@ end_io:
 
 		if (test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))
 			goto end_io;
+		if (test_bit(QUEUE_FLAG_RDONLY, &q->queue_flags)
+				&& bio->bi_rw == WRITE)
+			goto end_io;
 
 		/*
 		 * If this device has partitions, remap block n
@@ -2867,6 +2870,52 @@ void blk_unregister_queue(struct gendisk
 	}
 }
 
+#define MAX_RDONLY_DEVS		16
+
+static struct block_device *rdonly_devs[MAX_RDONLY_DEVS] = {0, };
+
+/*
+ * Debug code for turning block devices "read-only" (will discard writes
+ * silently).  This is for filesystem crash/recovery testing.
+ */
+void dev_set_rdonly(struct block_device *bdev, int no_write)
+{
+	if (bdev) {
+		request_queue_t *q;
+
+		q = bdev_get_queue(bdev);
+		if (!q) {
+			printk(KERN_ERR
+				"dev_set_rdonly() for non-existing device\n");
+			return;
+		}
+		printk(KERN_WARNING "Turning device %s read-only\n",
+				bdev->bd_disk ? bdev->bd_disk->disk_name : "?");
+		set_bit(QUEUE_FLAG_RDONLY, &q->queue_flags);
+		rdonly_devs[no_write] = bdev;
+	}
+}
+
+void dev_clear_rdonly(int no_write)
+{
+	request_queue_t *q;
+	
+	if (rdonly_devs[no_write] == NULL)
+		return;
+	
+	q = bdev_get_queue(rdonly_devs[no_write]);
+	if (!q) {
+		printk(KERN_ERR
+			"dev_clear_rdonly: no queue for device at slot %d\n",
+			no_write);
+		return;
+	}
+	clear_bit(QUEUE_FLAG_RDONLY, &q->queue_flags);
+	rdonly_devs[no_write] = NULL;
+}
+
+EXPORT_SYMBOL(dev_set_rdonly);
+EXPORT_SYMBOL(dev_clear_rdonly);
 
 EXPORT_SYMBOL(process_that_request_first);
 EXPORT_SYMBOL(end_that_request_first);
--- linux-2.6.0-test6/include/linux/blkdev.h~dev_read_only_2.6.0	2003-10-14 19:57:05.000000000 +0400
+++ linux-2.6.0-test6-alexey/include/linux/blkdev.h	2003-10-21 23:31:18.000000000 +0400
@@ -367,6 +367,7 @@ struct request_queue
 #define	QUEUE_FLAG_READFULL	3	/* write queue has been filled */
 #define QUEUE_FLAG_WRITEFULL	4	/* read queue has been filled */
 #define QUEUE_FLAG_DEAD		5	/* queue being torn down */
+#define QUEUE_FLAG_RDONLY	6	/* queue accepts reads only */
 
 #define blk_queue_plugged(q)	!list_empty(&(q)->plug_list)
 #define blk_queue_tagged(q)	test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)

_