From: Jens Axboe <axboe@suse.de>

Following some consideration, I think it's better to simply always invoke
the request_fn even if the device wasn't plugged if someone unplugs it. 
This solves the problem of md + dm setting the plugged bit unconditionally
_outside_ of the queue lock, thus confusing some drivers that checks this
bit for sanity in the request_fn.


---

 /dev/null                         |    0 
 25-akpm/drivers/block/ll_rw_blk.c |    2 +-
 25-akpm/drivers/md/dm.c           |    1 -
 25-akpm/drivers/md/md.c           |    5 +----
 drivers/md/dm-table.c             |    0 
 5 files changed, 2 insertions(+), 6 deletions(-)

diff -puN drivers/block/ll_rw_blk.c~per-backing_dev-unplugging-dm-md-rethink drivers/block/ll_rw_blk.c
--- 25/drivers/block/ll_rw_blk.c~per-backing_dev-unplugging-dm-md-rethink	2004-03-17 02:23:34.770201872 -0800
+++ 25-akpm/drivers/block/ll_rw_blk.c	2004-03-17 02:24:29.705850384 -0800
@@ -1138,7 +1138,7 @@ static inline void __generic_unplug_devi
 	 * always call down, since we can race now with setting the plugged
 	 * bit outside of the queue lock
 	 */
-	(void) blk_remove_plug(q);
+	blk_remove_plug(q);
 
 	/*
 	 * was plugged, fire request_fn if queue has stuff to do
diff -puN drivers/md/dm.c~per-backing_dev-unplugging-dm-md-rethink drivers/md/dm.c
--- 25/drivers/md/dm.c~per-backing_dev-unplugging-dm-md-rethink	2004-03-17 02:23:34.772201568 -0800
+++ 25-akpm/drivers/md/dm.c	2004-03-17 02:23:34.784199744 -0800
@@ -580,7 +580,6 @@ static void dm_unplug_all(request_queue_
 	struct mapped_device *md = q->queuedata;
 	struct dm_table *map = dm_get_table(md);
 
-	clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
 	if (map) {
 		dm_table_unplug_all(map);
 		dm_table_put(map);
diff -puN drivers/md/dm-table.c~per-backing_dev-unplugging-dm-md-rethink drivers/md/dm-table.c
diff -puN drivers/md/md.c~per-backing_dev-unplugging-dm-md-rethink drivers/md/md.c
--- 25/drivers/md/md.c~per-backing_dev-unplugging-dm-md-rethink	2004-03-17 02:23:34.776200960 -0800
+++ 25-akpm/drivers/md/md.c	2004-03-17 02:23:37.173836464 -0800
@@ -171,10 +171,8 @@ void md_unplug_mddev(mddev_t *mddev)
 	ITERATE_RDEV(mddev, rdev, tmp) {
 		request_queue_t *r_queue = bdev_get_queue(rdev->bdev);
 
-		if (r_queue->unplug_fn) {
-			set_bit(QUEUE_FLAG_PLUGGED, &r_queue->queue_flags);
+		if (r_queue->unplug_fn)
 			r_queue->unplug_fn(r_queue);
-		}
 	}
 }
 EXPORT_SYMBOL(md_unplug_mddev);
@@ -183,7 +181,6 @@ static void md_unplug_all(request_queue_
 {
 	mddev_t *mddev = q->queuedata;
 
-	clear_bit(QUEUE_FLAG_PLUGGED, &q->queue_flags);
 	md_unplug_mddev(mddev);
 }
 
diff -puN -L opt/kernel/linux-2.6.5-rc1-mm1/drivers/block/ll_rw_blk.c /dev/null /dev/null
diff -puN -L opt/kernel/linux-2.6.5-rc1-mm1/drivers/md/dm.c /dev/null /dev/null
diff -puN -L opt/kernel/linux-2.6.5-rc1-mm1/drivers/md/dm-table.c /dev/null /dev/null
diff -puN -L opt/kernel/linux-2.6.5-rc1-mm1/drivers/md/md.c /dev/null /dev/null

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