Commit efee1713 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Linus Torvalds
Browse files

mm: simplify bdi refcounting 

Move grabbing and releasing the bdi refcount out of the common
wb_init/wb_exit helpers into code that is only used for the non-default
memcg driven bdi_writeback structures.

[hch@lst.de: add comment]
  Link: https://lkml.kernel.org/r/20211027074207.GA12793@lst.de
[akpm@linux-foundation.org: fix typo]

Link: https://lkml.kernel.org/r/20211021124441.668816-6-hch@lst.de


Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJan Kara <jack@suse.cz>
Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 702f2d1e

include/linux/backing-dev-defs.h

+3 −0
Original line number Diff line number Diff line
@@ -103,6 +103,9 @@ struct wb_completion { 
 * change as blkcg is disabled and enabled higher up in the hierarchy, a wb

 * is tested for blkcg after lookup and removed from index on mismatch so

 * that a new wb for the combination can be created.

 *

 * Each bdi_writeback that is not embedded into the backing_dev_info must hold

 * a reference to the parent backing_dev_info.  See cgwb_create() for details.

 */

struct bdi_writeback {

	struct backing_dev_info *bdi;	/* our parent bdi */

mm/backing-dev.c

+5 −8
Original line number Diff line number Diff line
@@ -291,8 +291,6 @@ static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi, 


	memset(wb, 0, sizeof(*wb));



	if (wb != &bdi->wb)

		bdi_get(bdi);

	wb->bdi = bdi;

	wb->last_old_flush = jiffies;

	INIT_LIST_HEAD(&wb->b_dirty);
@@ -316,7 +314,7 @@ static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi, 


	err = fprop_local_init_percpu(&wb->completions, gfp);

	if (err)

		goto out_put_bdi;

		return err;



	for (i = 0; i < NR_WB_STAT_ITEMS; i++) {

		err = percpu_counter_init(&wb->stat[i], 0, gfp);
@@ -330,9 +328,6 @@ static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi, 
	while (i--)

		percpu_counter_destroy(&wb->stat[i]);

	fprop_local_destroy_percpu(&wb->completions);

out_put_bdi:

	if (wb != &bdi->wb)

		bdi_put(bdi);

	return err;

}
@@ -373,8 +368,6 @@ static void wb_exit(struct bdi_writeback *wb) 
		percpu_counter_destroy(&wb->stat[i]);



	fprop_local_destroy_percpu(&wb->completions);

	if (wb != &wb->bdi->wb)

		bdi_put(wb->bdi);

}



#ifdef CONFIG_CGROUP_WRITEBACK
@@ -397,6 +390,7 @@ static void cgwb_release_workfn(struct work_struct *work) 
	struct bdi_writeback *wb = container_of(work, struct bdi_writeback,

						release_work);

	struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);

	struct backing_dev_info *bdi = wb->bdi;



	mutex_lock(&wb->bdi->cgwb_release_mutex);

	wb_shutdown(wb);
@@ -416,6 +410,7 @@ static void cgwb_release_workfn(struct work_struct *work) 


	percpu_ref_exit(&wb->refcnt);

	wb_exit(wb);

	bdi_put(bdi);

	WARN_ON_ONCE(!list_empty(&wb->b_attached));

	kfree_rcu(wb, rcu);

}
@@ -497,6 +492,7 @@ static int cgwb_create(struct backing_dev_info *bdi, 
	INIT_LIST_HEAD(&wb->b_attached);

	INIT_WORK(&wb->release_work, cgwb_release_workfn);

	set_bit(WB_registered, &wb->state);

	bdi_get(bdi);



	/*

	 * The root wb determines the registered state of the whole bdi and
@@ -528,6 +524,7 @@ static int cgwb_create(struct backing_dev_info *bdi, 
	goto out_put;



err_fprop_exit:

	bdi_put(bdi);

	fprop_local_destroy_percpu(&wb->memcg_completions);

err_ref_exit:

	percpu_ref_exit(&wb->refcnt);