[PATCH v8 4/8] writeback, cgroup: switch to rcu_work API in inode_switch_wbs()

Roman Gushchin
2021-06-08T01:31:19Z

Inode's wb switching requires two steps divided by an RCU grace
period. It's currently implemented as an RCU callback
inode_switch_wbs_rcu_fn(), which schedules inode_switch_wbs_work_fn()
as a work.

Switching to the rcu_work API allows to do the same in a cleaner and
slightly shorter form.

Signed-off-by: Roman Gushchin <guro@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
---
fs/fs-writeback.c | 18 ++++--------------
1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index e2cc860a001b..96974e13a203 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -335,8 +335,7 @@ struct inode_switch_wbs_context {
struct inode *inode;
struct bdi_writeback *new_wb;

- struct rcu_head rcu_head;
- struct work_struct work;
+ struct rcu_work work;
};

static void bdi_down_write_wb_switch_rwsem(struct backing_dev_info *bdi)
@@ -352,7 +351,7 @@ static void bdi_up_write_wb_switch_rwsem(struct backing_dev_info *bdi)
static void inode_switch_wbs_work_fn(struct work_struct *work)
{
struct inode_switch_wbs_context *isw =
- container_of(work, struct inode_switch_wbs_context, work);
+ container_of(to_rcu_work(work), struct inode_switch_wbs_context, work);
struct inode *inode = isw->inode;
struct backing_dev_info *bdi = inode_to_bdi(inode);
struct address_space *mapping = inode->i_mapping;
@@ -469,16 +468,6 @@ static void inode_switch_wbs_work_fn(struct work_struct *work)
atomic_dec(&isw_nr_in_flight);
}

-static void inode_switch_wbs_rcu_fn(struct rcu_head *rcu_head)
-{
- struct inode_switch_wbs_context *isw = container_of(rcu_head,
- struct inode_switch_wbs_context, rcu_head);
-
- /* needs to grab bh-unsafe locks, bounce to work item */
- INIT_WORK(&isw->work, inode_switch_wbs_work_fn);
- queue_work(isw_wq, &isw->work);
-}
-
/**
* inode_switch_wbs - change the wb association of an inode
* @inode: target inode
@@ -536,7 +525,8 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
* lock so that stat transfer can synchronize against them.
* Let's continue after I_WB_SWITCH is guaranteed to be visible.
*/
- call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
+ INIT_RCU_WORK(&isw->work, inode_switch_wbs_work_fn);
+ queue_rcu_work(isw_wq, &isw->work);
return;

out_free:
--
2.31.1