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Subject[PATCH 05/10] block: drop unnecessary blk_get/put_queue() in scsi_cmd_ioctl() and blk_get_tg()
Date
blk_get/put_queue() in scsi_cmd_ioctl() and throtl_get_tg() are
completely bogus. The caller must have a reference to the queue on
entry and taking an extra reference doesn't change anything.

For scsi_cmd_ioctl(), the only effect is that it ends up checking
QUEUE_FLAG_DEAD on entry; however, this is bogus as queue can die
right after blk_get_queue(). Dead queue should be and is handled in
request issue path (it's somewhat broken now but that's a separate
problem and doesn't affect this one much).

throtl_get_tg() incorrectly assumes that q is rcu freed. Also, it
doesn't check return value of blk_get_queue(). If the queue is
already dead, it ends up doing an extra put.

Drop them.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-throttle.c | 8 +-------
block/scsi_ioctl.c | 3 +--
2 files changed, 2 insertions(+), 9 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index f3f495e..ecba5fc 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -324,12 +324,8 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
/*
* Need to allocate a group. Allocation of group also needs allocation
* of per cpu stats which in-turn takes a mutex() and can block. Hence
- * we need to drop rcu lock and queue_lock before we call alloc
- *
- * Take the request queue reference to make sure queue does not
- * go away once we return from allocation.
+ * we need to drop rcu lock and queue_lock before we call alloc.
*/
- blk_get_queue(q);
rcu_read_unlock();
spin_unlock_irq(q->queue_lock);

@@ -339,13 +335,11 @@ static struct throtl_grp * throtl_get_tg(struct throtl_data *td)
* dead
*/
if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
- blk_put_queue(q);
if (tg)
kfree(tg);

return ERR_PTR(-ENODEV);
}
- blk_put_queue(q);

/* Group allocated and queue is still alive. take the lock */
spin_lock_irq(q->queue_lock);
diff --git a/block/scsi_ioctl.c b/block/scsi_ioctl.c
index 4f4230b..fbdf0d8 100644
--- a/block/scsi_ioctl.c
+++ b/block/scsi_ioctl.c
@@ -565,7 +565,7 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod
{
int err;

- if (!q || blk_get_queue(q))
+ if (!q)
return -ENXIO;

switch (cmd) {
@@ -686,7 +686,6 @@ int scsi_cmd_ioctl(struct request_queue *q, struct gendisk *bd_disk, fmode_t mod
err = -ENOTTY;
}

- blk_put_queue(q);
return err;
}
EXPORT_SYMBOL(scsi_cmd_ioctl);
--
1.7.3.1


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