[PATCH 3/6] bdi: remove bdi->wb_lock locking around bdi->dev clearing in bdi_unregister()

Tejun Heo
2014-09-07T23:05:01Z

The only places where NULL test on bdi->dev is used are
bdi_[un]register(). The functions can't be called in parallel anyway
and there's no point in protecting bdi->dev clearing with a lock.
Remove bdi->wb_lock grabbing around bdi->dev clearing and move it
after device_unregister() call so that bdi->dev doesn't have to be
cached in a local variable.

This patch shouldn't introduce any behavior difference.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
mm/backing-dev.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 1706cbb..4afeefe 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -402,21 +402,15 @@ static void bdi_prune_sb(struct backing_dev_info *bdi)

void bdi_unregister(struct backing_dev_info *bdi)
{
- struct device *dev = bdi->dev;
-
- if (dev) {
+ if (bdi->dev) {
bdi_set_min_ratio(bdi, 0);
trace_writeback_bdi_unregister(bdi);
bdi_prune_sb(bdi);

bdi_wb_shutdown(bdi);
bdi_debug_unregister(bdi);
-
- spin_lock_bh(&bdi->wb_lock);
+ device_unregister(bdi->dev);
bdi->dev = NULL;
- spin_unlock_bh(&bdi->wb_lock);
-
- device_unregister(dev);
}
}
EXPORT_SYMBOL(bdi_unregister);
--
1.9.3