writeback, cgroup: switch to rcu_work API in inode_switch_wbs()

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.

Link: https://lkml.kernel.org/r/20210608230225.2078447-5-guro@fb.com
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>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Jan Kara <jack@suse.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index e2cc860a001b968bff0f2a6febb984d9b3d1761d..96974e13a20358b31d87c05921294f60bc0a1236 100644 (file)
--- 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 @@ skip_switch:
        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: