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Commit ebe41ab0 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

writeback: implement bdi_for_each_wb() 



This will be used to implement bdi-wide operations which should be
distributed across all its cgroup bdi_writebacks.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 693108a8

include/linux/backing-dev.h

+63 −0
Original line number Diff line number Diff line
@@ -383,6 +383,61 @@ static inline struct bdi_writeback *inode_to_wb(struct inode *inode) 
	return inode->i_wb;

}



struct wb_iter {

	int			start_blkcg_id;

	struct radix_tree_iter	tree_iter;

	void			**slot;

};



static inline struct bdi_writeback *__wb_iter_next(struct wb_iter *iter,

						   struct backing_dev_info *bdi)

{

	struct radix_tree_iter *titer = &iter->tree_iter;



	WARN_ON_ONCE(!rcu_read_lock_held());



	if (iter->start_blkcg_id >= 0) {

		iter->slot = radix_tree_iter_init(titer, iter->start_blkcg_id);

		iter->start_blkcg_id = -1;

	} else {

		iter->slot = radix_tree_next_slot(iter->slot, titer, 0);

	}



	if (!iter->slot)

		iter->slot = radix_tree_next_chunk(&bdi->cgwb_tree, titer, 0);

	if (iter->slot)

		return *iter->slot;

	return NULL;

}



static inline struct bdi_writeback *__wb_iter_init(struct wb_iter *iter,

						   struct backing_dev_info *bdi,

						   int start_blkcg_id)

{

	iter->start_blkcg_id = start_blkcg_id;



	if (start_blkcg_id)

		return __wb_iter_next(iter, bdi);

	else

		return &bdi->wb;

}



/**

 * bdi_for_each_wb - walk all wb's of a bdi in ascending blkcg ID order

 * @wb_cur: cursor struct bdi_writeback pointer

 * @bdi: bdi to walk wb's of

 * @iter: pointer to struct wb_iter to be used as iteration buffer

 * @start_blkcg_id: blkcg ID to start iteration from

 *

 * Iterate @wb_cur through the wb's (bdi_writeback's) of @bdi in ascending

 * blkcg ID order starting from @start_blkcg_id.  @iter is struct wb_iter

 * to be used as temp storage during iteration.  rcu_read_lock() must be

 * held throughout iteration.

 */

#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id)		\

	for ((wb_cur) = __wb_iter_init(iter, bdi, start_blkcg_id);	\

	     (wb_cur); (wb_cur) = __wb_iter_next(iter, bdi))



#else	/* CONFIG_CGROUP_WRITEBACK */



static inline bool inode_cgwb_enabled(struct inode *inode)
@@ -445,6 +500,14 @@ static inline void wb_blkcg_offline(struct blkcg *blkcg) 
{

}



struct wb_iter {

	int		next_id;

};



#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id)		\

	for ((iter)->next_id = (start_blkcg_id);			\

	     ({	(wb_cur) = !(iter)->next_id++ ? &(bdi)->wb : NULL; }); )



static inline int inode_congested(struct inode *inode, int cong_bits)

{

	return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);