[PATCH] block: fix partition reload bug with non-elevator devices

[Jens Axboe]

The partition reload code was changed to quiesce the block
queue so that partition IO stats could safely hold a reference
to the partition table. elv_quiesce_{start,end} do not
properly work on non-elevator devices. Improve the helper
functions so that they don't care, this way we can use
the generic interface on partition reload without having
to check for queue structures or types.

Reported-by: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: Jens Axboe <jaxboe@xxxxxxxxxxxx>
---
 block/elevator.c         |   31 +++++++++++++++++++++++--------
 block/genhd.c            |   10 +---------
 fs/partitions/check.c    |    5 -----
 include/linux/elevator.h |    2 ++
 4 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/block/elevator.c b/block/elevator.c
index 282e830..5461075 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -590,11 +590,8 @@ void elv_drain_elevator(struct request_queue *q)
 /*
  * Call with queue lock held, interrupts disabled
  */
-void elv_quiesce_start(struct request_queue *q)
+void __elv_quiesce_start(struct request_queue *q)
 {
-	if (!q->elevator)
-		return;
-
 	queue_flag_set(QUEUE_FLAG_ELVSWITCH, q);
 
 	/*
@@ -610,11 +607,31 @@ void elv_quiesce_start(struct request_queue *q)
 	}
 }
 
-void elv_quiesce_end(struct request_queue *q)
+void elv_quiesce_start(struct request_queue *q)
+{
+	if (q->elevator) {
+		spin_lock_irq(q->queue_lock);
+		__elv_quiesce_start(q);
+		spin_unlock_irq(q->queue_lock);
+	}
+}
+
+void __elv_quiesce_end(struct request_queue *q)
 {
 	queue_flag_clear(QUEUE_FLAG_ELVSWITCH, q);
 }
 
+void elv_quiesce_end(struct request_queue *q)
+{
+	if (q->elevator) {
+		unsigned long flags;
+
+		spin_lock_irqsave(q->queue_lock, flags);
+		__elv_quiesce_end(q);
+		spin_unlock_irqrestore(q->queue_lock, flags);
+	}
+}
+
 void elv_insert(struct request_queue *q, struct request *rq, int where)
 {
 	int unplug_it = 1;
@@ -969,7 +986,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 	 * Turn on BYPASS and drain all requests w/ elevator private data
 	 */
 	spin_lock_irq(q->queue_lock);
-	elv_quiesce_start(q);
+	__elv_quiesce_start(q);
 
 	/*
 	 * Remember old elevator.
@@ -995,9 +1012,7 @@ static int elevator_switch(struct request_queue *q, struct elevator_type *new_e)
 	 * finally exit old elevator and turn off BYPASS.
 	 */
 	elevator_exit(old_elevator);
-	spin_lock_irq(q->queue_lock);
 	elv_quiesce_end(q);
-	spin_unlock_irq(q->queue_lock);
 
 	blk_add_trace_msg(q, "elv switch: %s", e->elevator_type->elevator_name);
 
diff --git a/block/genhd.c b/block/genhd.c
index a8adf96..7d4d860 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -930,14 +930,9 @@ static void disk_free_ptbl_rcu_cb(struct rcu_head *head)
 	struct disk_part_tbl *ptbl =
 		container_of(head, struct disk_part_tbl, rcu_head);
 	struct gendisk *disk = ptbl->disk;
-	struct request_queue *q = disk->queue;
-	unsigned long flags;
 
 	kfree(ptbl);
-
-	spin_lock_irqsave(q->queue_lock, flags);
-	elv_quiesce_end(q);
-	spin_unlock_irqrestore(q->queue_lock, flags);
+	elv_quiesce_end(disk->queue);
 }
 
 /**
@@ -962,10 +957,7 @@ static void disk_replace_part_tbl(struct gendisk *disk,
 	if (old_ptbl) {
 		rcu_assign_pointer(old_ptbl->last_lookup, NULL);
 
-		spin_lock_irq(q->queue_lock);
 		elv_quiesce_start(q);
-		spin_unlock_irq(q->queue_lock);
-
 		call_rcu(&old_ptbl->rcu_head, disk_free_ptbl_rcu_cb);
 	}
 }
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index b81bfc0..cf4d1ee 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -367,16 +367,13 @@ static void delete_partition_rcu_cb(struct rcu_head *head)
 	struct hd_struct *part = container_of(head, struct hd_struct, rcu_head);
 	struct gendisk *disk = part_to_disk(part);
 	struct request_queue *q = disk->queue;
-	unsigned long flags;
 
 	part->start_sect = 0;
 	part->nr_sects = 0;
 	part_stat_set_all(part, 0);
 	put_device(part_to_dev(part));
 
-	spin_lock_irqsave(q->queue_lock, flags);
 	elv_quiesce_end(q);
-	spin_unlock_irqrestore(q->queue_lock, flags);
 }
 
 void delete_partition(struct gendisk *disk, int partno)
@@ -398,9 +395,7 @@ void delete_partition(struct gendisk *disk, int partno)
 	kobject_put(part->holder_dir);
 	device_del(part_to_dev(part));
 
-	spin_lock_irq(q->queue_lock);
 	elv_quiesce_start(q);
-	spin_unlock_irq(q->queue_lock);
 
 	call_rcu(&part->rcu_head, delete_partition_rcu_cb);
 }
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 80a0ece..2d30300 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -122,7 +122,9 @@ extern void elv_completed_request(struct request_queue *, struct request *);
 extern int elv_set_request(struct request_queue *, struct request *, gfp_t);
 extern void elv_put_request(struct request_queue *, struct request *);
 extern void elv_drain_elevator(struct request_queue *);
+extern void __elv_quiesce_start(struct request_queue *);
 extern void elv_quiesce_start(struct request_queue *);
+extern void __elv_quiesce_end(struct request_queue *);
 extern void elv_quiesce_end(struct request_queue *);
 
 /*
-- 
1.7.3


-- 
Jens Axboe

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